How would people find a city that is always moving?

Question: I have a country of desert nomads called Sahid, and the capital city is called 'Al'magor the wandering city.' This being literal, how would people be able to find this city easily? I have imagined the city crawling through the desert on stubby insect-like legs
Comment: half-serious: just follow the trace of waste and excrements?
Comment: How this city travels? I mean, a flying city will be much harder to track than floating city, which is harder to track than "walking" city (which leaves track. pun intended)
Comment: We may need more information. Desert nomads don't normally have walking machines, do they have technology or magic? How fast is the city? If it was fast enough it could be following even a clear trail is non-viable. How often do people leave, and how far do they go?
Comment: You could stay in one place and eventually it would come to you. Though it might be a long wait.
Comment: Go read Mortal Engines by Phillip Reeve. Cities have tracks and wheels instead of legs, but it's pretty much what you are asking.
Answer: Something the size of a city could be found by the devastation it leaves behind and the clouds of dust it lifts. Also it would be followed by their own inhabitants, scavenging wood, game, fruits, fish...
If not, just act like with any other animal: find the biggest source of water and sooner or later the city will need to come near it. Even a small city of a thousand people needs a lot of water each day just for drinking
Answer: Moving a city around just for the sake of moving it is a massive waste of resources. You haven't explained why the city needs to move, so let's assume it travels from oasis to oasis depending on the season.
Moving your city around isn't going to cheap. It will take a massive amount of energy. Whether it's magic or food or fuel, something is going to have to power the movement. Therefore, your city should always be taking the shortest possible route from one place to another.
As long as the destination is known, any resident of the city should be able to make a very good approximation of its location based on its known speed and its current route. For example, if your city is 5 days into the 20-day journey from A to B, you can estimate that it is 1/4th of the way from A to B along the standard travel route. With something that large, it doesn't even need to be a precise estimate.
If your city is wandering around aimlessly, it will be much harder to find. If the city is being moved around to hide it from attackers, the residents are probably doing their best to disguise its course, so the best solution would probably be prearranged meeting points (maybe it wanders aimlessly for 2 months and then makes a 3-day stop in Oasis A, so you just need to be in Oasis A during that 3-day stop).
If it isn't being moved for the sake of hiding it, the best solution is to use smoke signals. A pillar of smoke is visible for many miles and would make it easy for your nomads to relocate the city.
Answer: Cycles
Perhaps the city moves in a predictable pattern. Maybe it follows the migration of certain animals. Maybe it just moves between oases that dry up and then it has to move to another to let them replenish. Or maybe it just follows a celestial cycle related to its cosmic masters.
Communication
If the wandering city is inhabited, perhaps the citizens send out messengers periodically to let the rest of the world know where it's heading. I mean, if it's the capital lots of people will be interested in where it is, and presumably it's not moving very fast. So, even transmitting information by the speed of horse and carrier pigeon, it should be possible to keep the city's general whereabouts known.
Also, smoke in the day and lights at night could make the city visible from a considerable distance even beyond the horizon, so seekers would only have to get within a few dozen miles to be sure of its location.
Direction
Related to Communication, perhaps the inhabitants can control or influence where it goes, and thus make a schedule which can be shared.
Answer: Seems like they can't find their capital city easily; this is why they are nomads...
More seriously, @Harabeck I think has the right idea, which is that the people in the city can be sending out messengers.  The Mongols, famously nomadic, had a nice courier system that you could borrow:  https://en.wikipedia.org/wiki/Yam_(route)
Your messengers could have established routes ... messenger X periodically goes to a given oasis.  He tells everyone there the latest scoop on the city's location and vector and importantly, takes a bunch of homing pigeons back to the city.  Then he can send word via pigeon until he runs out, as which point he goes back to the oasis for another batch.
Over time, these oases might become more important to the people than the nominal capital, because they're reliable.  They stay where they belong, and you can always find them when you want them.


Buffy in mental hospital

Question: In one of the Buffy episodes, there is a quick flash of a scene where she is in a mental hospital. Was it ever resolved why this scene was shown? I seem to remember the implication being that her whole life was a mental breakdown.
Comment: Any chance the answer below might be accepted?  No new info has turned up for almost two years.
Comment: Go on then, because it's you
Comment: You're a dear.  :-)
Answer: The episode you are referring to is "Normal Again".  It isn't a "quick flash of a scene".  The entire episode is a tug of war between her being in a mental institution (in which the doctor and her parents are trying to convince her that being a slayer is a delusion) and the life we are accustomed to seeing her lead in Sunnydale.

Ostensibly, the mental institution is the delusion (rather than her life as a slayer), and the visions of the mental institution are brought on after Buffy is stung by a demon, thereby exposing her to a hallucinogenic venom.  In-universe, this is why we are seeing these scenes.
That being said, the episode ends in an ambiguous way, so as to suggest that her life as a slayer in Sunnydale might actually be the hallucination.
Out-of-universe, this is what led to the episode in question:

According to Joss Whedon, this episode was the "ultimate postmodern look at the concept of a writer writing a show", as it questioned fantastical or inconsistent elements of the show "the way any normal person would". Whedon added that the episode is intentionally left open to interpretation... "If the viewer wants," Whedon says, "the entire series takes place in the mind of a lunatic locked up somewhere in Los Angeles... and that crazy person is me." Although, "Personally, I think it really happened."

(Source, derived from here.)
Comment: The *ultimate* postmodern look at the concept of a writer writing a show. *Some*one has a high opinion of himself, *hmmm?*
Comment: @Beta: well, yeah. He created *Buffy the Vampire Slayer*, and wrote and directed many of its best episodes. Opinion is accurately high.
Comment: IIRC - the demon didn't bite Buffy - it stabbed her with a needle thing on its arm...
Comment: @JonClements : Was working off of memory.  Corrected --- thanks.

Buffy in mental hospital


Is the 'finally' portion of a 'try ... catch ... finally' construct/structure even necessary?

Question: Some languages (such as C++ and early versions of PHP) don't support the finally part of a try ... catch ... finally construct. Is finally ever necessary? Because the code in it always runs, why wouldn't/shouldn't I just place that code after a try ... catch block without a finally clause? Why use one? (I'm looking for a reason/motivation for using/not using finally, not a reason to do away with 'catch' or why it's legal to do so.)
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/20632/discussion-on-question-by-agi-hammerthief-is-the-finally-portion-of-a-try).
Answer: As others have mentioned, there's no guarantee that code after a try statement will execute unless you catch every possible exception. That said, this:
try {
   mightThrowSpecificException();
} catch (SpecificException e) {
   handleError();
} finally {
   cleanUp();
}

can be rewritten1 as:
try {
   mightThrowSpecificException();
} catch (SpecificException e) {
   try {
       handleError();
   } catch (Throwable e2) {
       cleanUp();
       throw e2;
   }
} catch (Throwable e) {
   cleanUp();
   throw e;
}
cleanUp();

But the latter requires you to catch all unhandled exceptions, duplicate the cleanup code, and remember to re-throw. So finally isn't necessary, but it's useful.
C++ doesn't have finally because Bjarne Stroustrup believes RAII is better, or at least suffices for most cases:

Why doesn't C++ provide a "finally" construct?
Because C++ supports an alternative that is almost always better: The "resource acquisition is initialization" technique (TC++PL3 section 14.4). The basic idea is to represent a resource by a local object, so that the local object's destructor will release the resource. That way, the programmer cannot forget to release the resource.

1 The specific code to catch all exceptions and rethrow without losing stack trace information varies by language. I have used Java, where the stack trace is captured when the exception is created. In C# you'd just use throw;.
Comment: You also have to catch the Exceptions in `handleError()` in the second case, no?
Comment: @AgiHammerthief The nested `try` is inside the `catch` for the *specific* exception. Secondly, it's possible you don't know whether you can handle the error successfully until you've examined the exception, or that the cause of the exception also prevents you from handling the error (at least at that level). That's fairly common when doing I/O. The rethrow is there because the only way to guarantee `cleanUp` runs is to catch *everything*, but the original code would allow exceptions originating in the `catch (SpecificException e)` block to propagate upwards.
Comment: You may also be throwing an error. I would rephrase that `catch (Throwable t) {}`, with the try .. catch block around the entire initial block (to catch throwables from `handleError` as well)
Comment: I'd actually add the extra try-catch you omitted when calling `handleErro();` which will make it even better argument as to why finally blocks are useful (even though that was not the original question).
Comment: This answer doesn't really address the question of why C++ doesn't have `finally`, which is a lot more nuanced.
Comment: @JuriRobl: Indeed so.  Incidentally, it may be interesting to note that nowadays Java compilers are required to rewrite try/catch/finally constructs into the form indicated above (including a catch within `handleError`); this could in some situations involving N nested try/finally blocks require the cleanup code to be expanded out an exponential number of times.
Comment: Why are you using a nested `try ... catch` in your catch for a general exception? Surely a `handleError()` function that might throw an exception is badly coded? Why rethrow a caught exception? What am I missing?
Comment: @AgiHammerthief so that it gets logged by the top-level exception handler?
Answer: In addition to what others have said, it's also possible for an exception to be thrown inside the catch clause. Consider this:
try {
    throw new SomeException();
} catch {
    DoSomethingWhichUnexpectedlyThrows();
}
Cleanup();

In this example, the Cleanup() function never runs, because an exception gets thrown in the catch clause and the next highest up catch in the call stack will catch that. Using a finally block removes this risk, and makes the code cleaner to boot.
Comment: Thank you for a concise and direct answer that doesn't digress into theory and 'language X is better than Y' territory.
Answer: finally blocks are usually used to clear up resources which can help with readability when using multiple return statements:
int DoSomething() {
    try {
        open_connection();
        return get_result();
    }
    catch {
        return 2;
    }
    finally {
        close_connection();
    }
}

vs
int DoSomething() {
    int result;
    try {
        open_connection();
        result = get_result();
    }
    catch {
        result = 2;
    }
    close_connection();
    return result;
}

Comment: Perhaps even more common is returning inside the try block, rather than inside the catch block.
Comment: To my mind, the code doesn't adequately explain the use of `finally`. (I'd use code as in the second block as multiple return statements are discouraged where I work.)
Answer: As you've apparently already surmised, yes, C++ provides the same capabilities without that mechanism. As such, strictly speaking, the try/finally mechanism is not really necessary.
That said, doing without it does impose some requirements on the way the rest of the language is designed. In C++ the same set of actions is embodied in a class' destructor. This works primarily (exclusively?) because destructor invocation in C++ is deterministic. This, in turn, leads to some rather complex rules about object lifetimes, some of which are decidedly non-intuitive.
Most of the other languages provide some form of garbage collection instead. While there are things about garbage collection that are controversial (e.g., its efficiency relative to other methods of memory management) one thing generally isn't: the exact time when an object will be "cleaned up" by the garbage collector is not tied directly to the scope of the object. This prevents its use when cleanup needs to be deterministic either when it's simply required for correct operation, or when dealing with resources so precious that their cleanup most not be delayed arbitrarily. try/finally provides a way for such languages to deal with those situations that require that deterministic cleanup.
I think those claiming that C++ syntax for this capability is "less friendly" than Java's are rather missing the point. Worse, they're missing a much more crucial point about the division of responsibility that goes far beyond syntax, and has a great deal more to do with how code is designed.
In C++, this deterministic cleanup happens in the object's destructor. That means the object can be (and normally should be) designed to clean up after itself. This goes to the essence of object oriented design--a class should be designed to provide an abstraction, and enforce its own invariants. In C++, one does precisely that--and one of the invariants for which it provides is that when the object is destroyed, the resources controlled by that object (all of them, not just memory) will be destroyed correctly.
Java (and similar) are somewhat different. While they do (sort of) support a finalize that could theoretically provide similar capabilities, the support is so weak that it's basically unusable (and in fact, essentially never used).
As a result, rather than the class itself being able to do the required cleanup, the client of the class needs to take steps to do so. If we do a sufficiently short-sighted comparison, it can at first glance appear that this difference is fairly minor and Java is quite competitive with C++ in this respect. We end up with something like this. In C++, the class looks something like this:
class Foo {
    // ...
public:
    void do_whatever() { if (xyz) throw something; }
    ~Foo() { /* handle cleanup */ }
};

...and the client code looks something like this:
void f() {
    Foo f;
    f.do_whatever();
    // possibly more code that might throw here
}

In Java we exchange a little more code where the object is used for a little less in the class. This initially looks like a pretty even trade-off. In reality, it's far from it though, because in most typical code we only define the class in one place, but we use it many places. The C++ approach means we only write that code to handle the cleanup in one place. The Java approach means we have to write that code to handle the cleanup many times over, in many places--every place we use an object of that class.
In short, the Java approach basically guarantees that many abstractions we try to provide are "leaky"--any and every class that requires deterministic cleanup obliges the client of the class to know about the details of what to cleanup and how to do the cleanup, rather than those details being hidden in the class itself.
Although I've called it "the Java approach" above, try/finally and similar mechanisms under other names aren't entirely restricted to Java. For one prominent example, most (all?) of the .NET languages (e.g., C#) provide the same.
Recent iterations of both Java and C# also provide something of a halfway point between "classic" Java and C++ in this regard. In C#, an object that wants to automate its cleanup can implement the IDisposable interface, which provides a Dispose method that's (at least vaguely) similar to a C++ destructor. While this can be used via a try/finally like in Java, C# automates the task a little more with a using statement that lets you define resources that will be created as a scope is entered, and destroyed when the scope is exited. Though still well short of the level of automation and certainty provided by C++, this is still a substantial improvement over Java. In particular, the class designer can centralize the details of how to dispose of the class in its implementation of IDisposable. All that's left for the client programmer is the lesser burden of writing a using statement to assure that the IDisposable interface will be used when it should be. In Java 7 and newer, the names have been changed to protect the guilty, but the basic idea is basically identical.
Comment: Perfect answer. Destructors are **THE** must-have feature in C++.
Comment: Similar to IDisposable, python offers `with` [context managers](https://docs.python.org/3/reference/datamodel.html#context-managers).
Answer: Can't believe nobody else has raised this (no pun intended) - you don't need a catch clause!
This is perfectly reasonable:
try
{
   AcquireManyResources();
   DoSomethingThatMightFail();
}
finally
{
   CleanUpThoseResources();
}

No catch clause anywhere is sight, because this method can't do anything useful with those exceptions; they are left to propagate back up the call stack to a handler that can.  Catching and re-throwing exceptions in every method is a Bad Idea, especially if you're just re-throwing the same exception.  It completely goes against how Structured Exception Handling is supposed to work (and is pretty close to returning an "error code" from every method, just in the "shape" of an Exception).
What this method does have to do, though, it to clean up after itself, so that the "Outside World" never needs to know anything about the mess that it got itself into.  The finally clause does just that - no matter how the called methods behave, the finally clause will be executed "on the way out" of the method (and the same is true for every finally clause between the point at which the Exception is thrown and the eventual catch clause that handles it); each one is run as the call stack "unwinds".
Answer: What would happen if and exception was thrown that you were not expecting. The try would exit in the middle of it and no catch clause is executed.
The finally block is to help with that and ensure that no matter the exception the cleanup will happen.
Comment: That's not sufficient reason for a `finally`, as you can prevent "unexpected" exceptions with `catch(Object)` or `catch(...)` catch-alls.
Comment: Which sounds like a work around. Conceptually finally is cleaner. Though I must confess to rarely using it.
Answer: Some languages offer both constructors and destructors for their objects (e.g. C++ I believe). With these languages you can do most (arguably all) of what is usually done in finally in a destructor. As such - in those languages - a finally clause may be superfluous.
In a language without destructors (e.g. Java) it is difficult (maybe even impossible) to achieve correct cleanup without the finally clause. NB - In Java there is a finalise method but there is no guarantee it will ever be called.
Comment: It may be useful to note that destructors help with cleaning resources when destruction is *deterministic*. If we don't know when the object will be destructed and/or garbage-collected, then destructors are not safe enough.
Comment: @Morwenn - Good point. I hinted at it with my reference to Java's `finalise` but I would prefer not to get into the political arguments around destructors/finalies at this time.
Comment: In C++ destruction is deterministic. When the scope containing an automatic object exits (e.g. it gets popped off the stack), its destructor is called. (C++ allows you to allocate objects on the stack, not just the heap.)
Comment: @RobK - And this is the exact functionality of a `finalise` but with both an extensible flavor and an oop-like mechanism - very expressive and comparable to the `finalise` mechanism of other languages.
Answer: Try finally and try catch are two different things which only share the: "try" keyword.
Personally I would have like to see that different. The reason you see them together is because exceptions produce a "jump".
And try finally is designed to run code even if programming flow jumps out. Whether that be because of an exception or any other reason. It's a neat way to acquire a resource and make sure it's cleaned up after without having to worry about jumps.
Comment: In .NET they are implemented using separate mechanisms; in Java, however, the only construct recognized by the JVM is semantically equivalent to "on error goto", a pattern which directly supports `try catch` but not `try finally`; code using the latter is converted into code using only the former, by copying the content of the `finally` block in all spots of the code where it might need to execute.
Comment: @supercat nice, thanks for the extra info about Java.
Answer: Since this question doesn't specify C++ as a language I'll consider a mix of C++ and Java, since they take a different approach to object destruction, which is getting suggested as one of the alternatives.
Reasons you might use a finally block, rather than code after the try-catch block

you return early from the try block: Consider this
Database db = null;
try {
 db = open_database();
 if(db.isSomething()) {
   return 7;
 }
 return db.someThingElse();
} finally {
  if(db!=null)
    db.close();
}

compared with:
Database db = null;
int returnValue = 0;
try {
 db = open_database();
 if(db.isSomething()) {
   returnValue = 7;
 } else {
   returnValue = db.someThingElse();
 }
} catch(Exception e) {
  if(db!=null)
    db.close();
}
return returnValue;

you return early from the catch block(s) :  Compare
Database db = null;
try {
 db = open_database();
 db.doSomething();
} catch (DBIntegrityException e ) {
  return 7;
} catch (DBIsADonkeyException e ) {
  return 11;
} finally {
  if(db!=null)
    db.close();
}

vs:
Database db = null;
try {
 db = open_database();
 db.doSomething();
} catch (DBIntegrityException e ) {
  if(db!=null)
    db.close();
  return 7;
} catch (DBIsADonkeyException e ) {
  if(db!=null)
    db.close();
  return 11;
}
db.close();

You rethrow exceptions. Compare:
Database db = null;
try {
 db = open_database();
 db.doSomething();
} catch (DBIntegrityException e ) {
  throw convertToRuntimeException(e,"DB was wonkey");
} finally {
  if(db!=null)
    db.close();
}

vs:
Database db = null;
try {
 db = open_database();
 db.doSomething();
} catch (DBIntegrityException e ) {
  if(db!=null)
    db.close();
  throw convertToRuntimeException(e,"DB was wonkey");
}
if(db!=null)
  db.close();

These examples don't make it seem too bad, but often you have several of these cases interacting and more than one exception/resource type in play. finally can help keep your code from becoming a tangled maintenance nightmare.
Now in C++ these can be handled with scope based objects. But IMO there are two disadvantges to this approach 1. syntax is less friendly. 2. Order of construction being the reverse of order of destruction can make things less clear.
In Java you can't hook the finalize method to do your cleanup since you don't know when it will happen - (well you can but thats a path filled with fun race conditions - JVM has a lot of scope in deciding when it destroys things - often its not when you expect it - either earlier or later than you might expect - and that can change as the hot-spot compiler kicks in... sigh...)
Answer: All that is logicaly  "necessary" in a programming language are the instructions:
assignment a = b
subtract a from b
goto label
test a = 0
if true goto label

Any algorithm can be implemented using only the instructions above, all other language constructs are there to make programs easier to write and more understandable to other programmers.
See oldie worldy computer for actual hardware using such a minimal instruction set.
Comment: Your answer is certainly true, but I don't code in assembly; it's too painful. I'm asking why use a feature I don't see the point of in languages that support it, not what the bare minimum instruction set of a language is.
Comment: The point is any language implementing just these 5 operations can implement any algorithm --  albeit rather tortuously. Most vers/operators in high level languages are not "necessary" if the goal is merely to implement an algorithm. If the goal is to have rapid development of readable maintainable code then most are necessary but "readable" and "maintainable" are not measurable and extremely subjective. The nice language developers put in lots of features: if you don't have a use for some of them then don't use them.
Answer: Actually the bigger gap to me is usually in the languages that support finally but lack destructors, because you can model all the logic associated with "cleanup" (which I'll separate into two categories) through destructors at a central level without manually dealing with cleanup logic in every relevant function. When I see C# or Java code doing things like manually unlocking mutexes and closing files in finally blocks, that feels outdated and kinda like C code when all of that is automated in C++ through destructors in ways that frees humans of that responsibility.
However, I would still find a mild convenience if C++ included finally and it's because there's two types of clean-ups:

Destroying/freeing/unlocking/closing/etc local resources (destructors are perfect for this).
Undoing/rolling back external side effects (destructors are adequate for this).

The second one at least doesn't map so intuitively to the idea of resource destruction, though you can do it just fine with scope guards which automatically roll back changes when they're destroyed prior to being committed. There finally arguably provides at least a slightly (just by a teeny bit) more straightforward mechanism for the job than scope guards.
However, an even more straightforward mechanism would be a rollback block which I've never seen in any language before. It's kind of a pipe dream of mine if I ever designed a language that involved exception-handling. It would resemble this:
try
{
    // Cause external side effects. These side effects should
    // be undone if we don't finish successfully.
}
rollback
{
    // Reverse external side effects. This block is *only* executed
    // if the 'try' block above faced a premature return out
    // of the function. It is different from 'finally' which
    // gets executed regardless of whether or not the function
    // exited prematurely. This block *only* gets executed if we
    // exited prematurely from  the try block so that we can undo
    // whatever side effects it failed to finish making. If the try
    // block succeeded and didn't face a premature exit, then we
    // don't want this block to execute.
}

That would be the most straightforward way to model side effect rollbacks, while destructors are pretty much the perfect mechanism for local resource cleanups. Now it only saves a couple extra lines of code from the scope guard solution, but the reason I so want to see a language with this in there is that side effect rollback tends to be the most neglected (but trickiest) aspect of exception-handling in languages that revolve around mutability. I think this feature would encourage developers to think about exception-handling the proper way in terms of rolling back transactions whenever functions cause side effects and fail to complete and, as a side bonus when people see how difficult it can be to do rollbacks properly, they might favor writing more functions free of side effects in the first place.
There are also some obscure cases where you just want to do miscellaneous things no matter what upon exiting a function, regardless of how it exited, like maybe logging a time stamp. There finally is arguably the most straightforward and perfect solution for the job, since trying to instantiate an object only to use its destructor for the sole purpose of logging a timestamp just feels really weird (even though you can do it just fine and quite conveniently with lambdas).
Answer: Like so many other unusual things about the C++ language, the lack of a try/finally construct is a design flaw, if you can even call it that in a language that frequently appears to not have had any actual design work done at all.
RAII (the use of scope-based deterministic destructor invocation on stack-based objects for cleanup) has two serious flaws.  The first is that it requires the use of stack based objects, which are an abomination that violate the Liskov Substitution Principle.  There are plenty of good reasons why no other OO language before or since C++ has used them--within epsilon; D doesn't count as it's based heavily on C++ and has no market share anyway--and explaining the problems they cause is beyond the scope of this answer.
Second, what finally can do is a superset of object destruction.  Much of what is done with RAII in C++ would be described in the Delphi language, which does not have garbage collection, with the following pattern:
myObject := MyClass.Create(arguments);
try
   doSomething(myObject);
finally
   myObject.Free();
end;

This is the RAII pattern made explicit; if you were to create a C++ routine that contains only the equivalent to the first and third lines above, what the compiler would generate would end up looking like what I wrote in its basic structure.  And because it's the only access to the try/finally construct that C++ provides, C++ developers end up with a rather myopic view of try/finally: when all you have is a hammer, everything starts to look like a destructor, so to speak.
But there are other things that an experienced developer can do with a finally construct.  It's not about deterministic destruction, even in the face of an exception being raised; it's about deterministic code execution, even in the face of an exception being raised.
Here's another thing you might commonly see in Delphi code:  A dataset object with user controls bound to it.  The dataset holds data from an external source, and the controls reflect the state of the data.  If you're about to load a bunch of data into your dataset, you will want to temporarily disable the data binding so that it doesn't do strange things to your UI, trying to update it over and over with every new record that's entered, so you would code it like this:
dataset.DisableControls();
try
   LoadData(dataset);
finally
   dataset.EnableControls();
end;

Clearly, there is no object being destroyed here, and no need for one.  The code is simple, concise, explicit, and efficient.
How would this be done in C++?  Well, first you would have to code up an entire class.  It would probably be called DatasetEnabler or somesuch thing.  Its entire existence would be as a RAII helper.  Then you would need to do something like this:
dataset.DisableControls();
{
   raiiGuard = DatasetEnabler(dataset);
   LoadData(dataset);
}

Yes, those apparently-superfluous curly braces are necessary to manage the proper scoping and ensure that the dataset gets re-enabled immediately and not at the end of the method.  So what you end up with does not take less lines of code (unless you use Egyptian braces).  It requires a superfluous object to be created, which has overhead. (Isn't C++ code is supposed to be fast?)  It is not explicit, but instead relies upon compiler magic.  The code that gets executed is described nowhere in this method, but instead resides in an entirely different class, possibly in an entirely different file.  In short, it is in no way a better solution than being able to write the try/finally block yourself.
This kind of problem is common enough in language design that there's a name for it: abstraction inversion.  It occurs when a high-level construct is built on top of a low-level construct, and then the low-level construct is not directly supported in the language, requiring those who wish to use it to re-implement it in terms of the high-level construct, often at steep penalties to both code readability and efficiency.
Comment: **Comments are meant to clarify or improve a question and answer.  If you would like to have a discussion about this answer then please go to the chat room.  Thank you.**


Prove that the function $g(x)=A_{x}$ is lower semicontinuous.

Question: Given $X\subseteq \Bbb R^m, f:X\to\Bbb R$ and $x\in X$, we say $f$ is lower semicontinous (l.s.c for short) at x if$\forall \varepsilon>0\ \exists\ \delta >0\ \forall \in B(\delta,x), \ f(x)\le f(y)+\varepsilon$. If x is a limit point of $X$, then f is lower semicontinuous iff $f(x)\le \lim_{\delta\to0^+}\ \inf\ f{\restriction}(X\cap B^*(\delta,y))$.
And, it is also given that $A\subseteq\Bbb R^m\times\Bbb R$, put $\pi(A)=\{x\in \Bbb R^m:\exists p\in \Bbb R,(x,p)\in A\}$, the projection of $A$ on $\Bbb R^m$. For $x\in\Bbb R^m$, put $A_x=\{p\in \Bbb R:(x,p)\in A\}$, the fiber of $A$ over $x$.
Then, I need to show: if $A\subseteq\Bbb R^m\times\Bbb R$ is compact and $g:\pi(A)\to\Bbb R$ is defined by $g(x)=\inf\ A_x$, then g is lower semicontinuous.
I got some idea about this problem, which is bu using the iff statement of limit inferior to show if g is not lsc, then it contradicts to the condition that $A$ is not compact. But I just do not know how to show this formally.
Answer: Assume that the iff statement is violated. Then you get $\varepsilon > 0$ and a sequence $x_n \to x$ with $g(x) > g(x_n) + \varepsilon$.. Now this should help you to get a contradiction with the definition of $g$ / the compacity of $A$.


Monster footsteps (animation)

Question: I've got a short animation I'm working on where a statue comes alive and wreaks havoc on a bunch of chickens. Lately, I'm having a bit of difficulty with its footsteps. I've been trying to use different types of boulder/rock crashing/exploding sounds as well as putting an LPF on rocket-type explosions and using fades to give them a shorter decay. Anybody have any other interesting ideas to try out/experience cutting to something like this?
Answer: On top of the footsteps, you should think about the effect the footsteps have on their surrounding environment. This could be rattling floorboards in a chicken coop, slapback from distant hills, debris falling, anything like that.
Answer: Pitch the chickens up a bit to give the contrast effect of the footsteps sounding deeper and lower.
Answer: How about thunder for the footsteps? I agree with Roger on the effects of the footsteps on the surrounding so perhaps some earthquake or avalanche type rumbling as well. The faster he walks, the bigger the 'earthquake' he causes.
Answer: Maybe something like an concert base drumb, maybe put some metallic pieces on it to give it that low rubble with a rattle. I really want to see this sequence, it sound great.
Answer: Heres something I discovered by accident once. I was doing a sound remix for fun and I was making footsteps of a giant robot monster that destroys buildings.  Open the sound of rubbing a balloon and use that, pitch it, whatever...
Answer: Wow, these are all some great ideas.
@Roger had definitely thought of that, since the monster is running around a temple ruin I'm messing a lot with additional smaller rock debris sounds, although your comment sparked the idea of its entrance affecting the BGs, having birds suddenly scattering.
@Tak I'll have to try out the thunder and let you know of the results.
@Peter I've got something kind of similar going on for my "bass" layer right now, some very deep footsteps that sound a bit like gigantic de-tuned drums.
@Chris That's...interesting. I'll have to mess with that to see what you mean, but did the balloon sound emulate the sound of bending steel in the buildings or something?

Monster footsteps (animation)


Do I need an RTC if my Raspberry Pi is continuously connected to the Internet?

Question: How accurate would the time on my Raspberry Pi 3 be if it is continuously connected to the Internet, but without an RTC?
Comment: The RTC isn't used for timekeeping when the system is up. It's one hwclock read on boot and one hwclock write on shutdown. When the system is up, HPET or other CPU timers are used, they are much more precise.
Comment: I don't now a precise answer, but it's a lot better than a second. How acurate do you need?
Comment: About 1 second accuracy would be good enough.
Answer: Because the NTP protocol attempts to measure and compensate for network latency and other delays, it is very accurate even when using public time servers.
RTC is used to maintain system time when power is removed, and it not necessarily even accurate, after your raspberry PI has booted up and received the time from NTP it will continue to count time without an RTC even if network is disconnected.
When using NTP you are not continuously synchronizing to the network, the system time is maintained with a timer based on the cpu clock.

When run with a local network time server, NTP can achieve accuracy of <1ms.
When run over the public internet, dynamic and potentially asymmetric routing of packets contributes to a poorer estimate of network delays. However, you can expect accuracy of well under 1s  with most documentation claiming an accuracy of 100ms over the public internet.
If you need better synchronization, without better accuracy, you may consider running a local NTP server to synchronize multiple raspberry pi relative to each other with better than 1ms synchronization (good for aligning sensor data) .
If you need both accuracy and synchronization, you can run a Stratum 1 NTP server using GPS as the time source.
Comment: In fact, on a good internet connection the error is usually in the single-digit milliseconds. Those specs are from when computers and network connections were both quite a bit slower.
Answer: According to wikipedia, the Network Time Protocol used by default on Raspbian and millions of other networked devices and computers:

is intended to synchronize all participating computers to within a few milliseconds

In fact, NTP is used on systems (servers, PCs, etc.) that have an RTC in order to correct for the drift computer clocks may have.  Meaning, if you added an RTC, it would be kept accurate by using the exact same network mechanisms that are used to set the OS "software" clock already (which, realistically, is tied to the processor frequency, i.e., there's crystal in there somewhere that effectively keeps the time while the system is on).
Answer: Presence or absence of RTC has nothing to do with timekeeping precision. It's purely a matter of being able to keep (a poor approximation of) current time while the device is powered down so that the system time is correct before you bring up the network device and ntpd.
Note that if you want a secure remote clock source rather than plain ntp, you'll need to know a rough idea of the current time (accurate within month scale) in order to validate certificates; this is probably the main modern purpose of an RTC on internet-connected devices.
Answer: Having done experiments with C++ on my RPI3 (Stretch) using the sys/time.h function gettimeofday(**) and the wiringPi API then measuring against a scope, streamlined applications can obtain sub-millisecond resolution and accuracy on timing.
Now if you are using other languages on the RPI you may not be able to obtain those speeds.
Answer: We get accuracy of better than a second on several units using a public NTP server the other side of a complex and busy network.  We also only need accuracy of the order of 1s (which the system clock can maintain for days while powered up).
Check out the ntpd man page, but after configuring a server, making sure that ntpd -g runs on boot should be all you need. The -g gets you back to real time if the clock is way out, such as after loss of power.
Comment: https://chrony.tuxfamily.org/comparison.html#Performance
Comment: `chrony` performs much better than `ntpd` on systems that might have their connection come and go at any time.
Comment: @hobbs that's interesting. Better in what way? Mine are wired because of an [issue with password storage](https://unix.stackexchange.com/q/242811/47326) and the connection is reliable. In fact they're more likely to lose power than network, but slowdowns sometimes happen.
Comment: In addition to the "unreliable network" operation, chrony can make a larger correction to the system clock frequency.  If the difference between nominal clock frequency and observed clock frequency is more than ±500 parts per million, ntpd will not correct it.  Basically, chrony works better in a virtual machine than ntpd.


SQL Server 2005 and SQL Server Express on the same machine?

Question: Can we have both version installed on the same computer?
Answer: Yes, you can even install SQL 2005 multiple times and multiple 2008 installs on the same computer.
Since quite some version SQL Server instances are named (with the exception of the default instance), and the express version has a defined different name.
Answer: yes, you can certainly. But you need to name the sql engine instance differently, such as sql express 2005 as sqlexpress2005, sql 2005 as sqlserver2005, sql server express 2008 as sqlexpress2008, sql server 2008 as sqlserver2008 etc.


Why do people answer old questions

Question: While browsing for an answer to a question I had, I found someone answered a question that was almost 3 years old. The post already has accepted answer. My question is: What's the use of answering old questions?
Comment: One could ask why do people answer *new* questions? Because we like to help. Same with old questions.
Comment: And what's the should be: a contemporary answer (or edit) or the more of recent ones... And the rule system that changed which accepted previous.
Answer: It could be useful to the original asker, who will be notified that another answer has been posted.
It will also be useful for those who find the post later, like you did, either through Stack Exchange or through Google.
It also can be important if the technologies or standards change, so that newer updated answers can be shown.
There are badges just for people who answer old questions.
Comment: *"t also can be important if the technologies or standards change"* [For example.](http://stackoverflow.com/a/17177156/2509)
Comment: Thanks...neatly explained
Answer: There are more than one ways to skin a cat. I don't know much about Android, but given that the answer has downvotes, I'm assuming its incorrect. However, if it were an valid alternate solution, there's a good chance that someone would find it later and find it useful.
I think it's been made pretty clear that SO isn't about the OP. It's more about the people coming to the question afterwards. Also, the OP will see the notification that an answer has been posted, and it could be helpful to them as well.
Answer: The poster of that answer explained in detail why he posted the answer:

[Stack Overflow] is a global knowledge base, which generally prevents you for asking new question if they already were covered. So for example if someone has the problem now, he/she still should use this question pile. So having an alternative answer is really valuable. So far no one marked as the answer post had value for me.

In other words, the accepted answer didn't work for him, and asking a new question would have caused a close as duplicate, so he posted what did work for him on the existing question.
Comment: Yes, I agree with you and the most reason to post the question here is to get the answer and clearing the misconception, that I got.

Why do people answer old questions


Which cuts of beef are suitable for slow cooking methods?

Question: If I want to simmer or braise a piece of beef for a few hours, how do I choose suitable meat? Which of the usual cuts are great, which are adequate, and which ones will just turn tough? It would be great if you could, beside giving a list of the good cuts, also give some advice on visually recognizing the good meat, in case I am faced with a supermarket selection with no labels (or misleading labels) and no qualified personnel.
Comment: How slow do you mean?  45 mins is probably the shortest long cook, but 1 hour, 3 hours and 6 hours are all possible and effect the beef selection
Comment: @NBenatar Interesting, I wasn't aware that there is a meat which can be slow cooked in 45 minutes. Are you talking about roasting a large cut of tender meat at once until the inside is medium rare? Because in my word usage, this is not slow cooking. But in case I am missing something, let's say cooking times of 3+ hours.
Comment: I'm not sure this question can be answered clearly without defining what "great" or "adequate" means. I don't think any beef generally "turns tough" when cooked *long enough*. Certain cuts when braised at too high temperature can become tough and "overdone" but will eventually soften when cooked longer. So, from my perspective, it then comes down to what you prefer in terms of texture, fat content, etc. Some people love the fattiness of chuck, while others (not as many) like a lean round or rump. You could braise a rib roast too, but most would consider that a waste since it's already tender.
Comment: @Athanasius I was not aware of such a possibility. To my knowledge, the very tender cuts (the ones normally cooked as steaks) don't have sufficient collagen to soften no matter how long you cook them. But maybe you can write an answer centered around that?
Answer: Beef for Slow cooking methods:
When shopping for beef that will be cooked long and slow, price per pound within a grade will be a helpful guide. Less tender cuts that will be best cooked long with liquid will be much less expensive than the naturally tender cuts that require less cooking i.e. filet mignon.
From http://life.familyeducation.com/

When shopping in the supermarket for meat destined for your slow cooker, here are the cuts to look for:
Shanks - Shoulder - Round - Rump
Even if they are not labeled as such, you'll know you've selected the
  proper slow cooker cuts when you compare the price of these cuts with
  cuts such as tenderloin, sirloin, and rib. And there is no need to go
  for the high-priced Prime grade meats. Choice and Standard quality are
  just fine.

To visually find the right cuts of beef for slow cooking look for:

Multiple muscle groups within the cut. In between each muscle is where you find the connective tissue that will break down. This shank has several.

Course grain is found in the working muscles of the animal. You can see the long fibers in this flank steak.

Fat - good marbling within the cut, but not too much on the exterior, like this pot roast.

A great guide to beef cuts can be found at chefsteps.com
Answer: For simmering and braising it's good to choose a working cut, that is from a load-bearing part of the animal, as this will have connective tissue which will break down into gelatin as it is cooked. These make terrible roasts but great braises and stews. The other consideration is fat content - you have to remember in a braise or stew the fat isn't going to be able to drip out, so if you have a fatty piece of meat you could end up with a greasy dish.
In the past I've gotten very good results from shin (leg, foreleg), brisket, flank, and silverside (round). Parts from the neck and shoulder I personally avoid as they often have lots of gristle and fat, making it work to get at the good meat. A decently butchered pot roast would do though.
One thing to remember is to get a good quality meat. In the US most of what you find in the stores is Select grade, which has a huge range in quality, so look for good color with decent marbling. You are getting a tough cut, so when touching don't expect much give. In fact, if you get lots of give with a working cut don't buy it - it's probably old.
Comment: You won't see good connective tissue, if you see it it's gristle. You are right that roasts aren't the best choice for slow cooking, however a pot roast isn't really a roast - the pot part means it should be cooked in a pot with liquid, in other words braised.
Comment: I've been told that a roast shouldn't be slow-cooked (see http://cooking.stackexchange.com/questions/43385/should-a-roast-be-covered-in-liquid-in-a-slow-cooker).  Can you provide a visual example of what good connective tissue looks like and how do I know the difference between connective tissue and gristle?
Comment: @GdD I am the one who mentioned visible marbling, and I am still convinced that the looks make a difference. Connective tissue is visible. And besides, gristle itself also provides collagen.
Comment: I would add cheek to this list - it's hard to get hold of and needs a long, slow braise, but the flavour and texture is amazing.
Answer: Short answer: Buy a cheap hunk of beef that looks like it has characteristics you like (e.g., lots of fat vs. little fat).  Cook slowly.  Enjoy.

I don't think there's a single answer to this question.  It all depends on the texture, flavor, and amount of fat you want, as well as what you're willing to pay.  The last consideration of cost is generally the driving factor for most people when slow-cooking.  Slow-cooking methods like braising are typically used for cheaper tougher cuts.
Basically, most people tend to like tender meat, and there's no way to make chuck or round (for example) very tender without prolonged cooking.  So we tend to use slow (and often moist) methods.  But the reverse isn't true for tender cuts: you could cook a tenderloin or a rib roast and braise them like a pot roast.  But there's little reason to, since you can find cheaper cuts that have similar textures and flavors.  (That said, I have had a long-cooked braised ribeye once, and it was one of the best "pot roast" type meats I've ever eaten.)
From my perspective, any cut of beef is theoretically "suitable" for slow cooking.  Braising, like long pit-roasting, is a "catch-all" cooking method that will work for just about anything.  All meat will eventually break down and soften if cooked long enough.  Many people tend to like meats that have a lot of collagen, fat, and other connective tissue to break down -- such as chuck, short ribs, or even less common cuts like oxtail.  These end up with a significant "succulent" texture after the beef breaks down, which many people find desirable.
On the other hand, I know people who find cuts like chuck to be way too fatty for their taste.  They're perfectly content with a leaner cut from the round, for example, to make a leaner pot roast, usually served with flavorful gravy or sauce.  It's all a matter of preference.
Some people like the strong "beefy" flavor that can come from bony areas like a shank (sometimes seen as a shin or leg cut) or oxtail, or even more "variety meat" elements like tongue or heart.  These are all great candidates for slow-cooking methods, if you want that much flavor.  Others prefer milder cuts.
Now, you could use ribeye instead of chuck for a fatty result, or use sirloin or even filet mignon instead of round for a lean result, and end up with a similar end-product.  But why would you spend the money?  (Actually, there is a bit of a disadvantage to using tenderloin/filet, since it doesn't have as much flavor as lean tougher cuts like round.  But there's no reason you couldn't braise a tenderloin for several hours; some people may actually prefer milder flavors.  Everyone has their own preferences.)
The one advantage to using a tender cut for slow cooking is that it will soften again faster.  Where a chuck roast might need 6-8 hours (or more) in a slow cooker to become tender, a rib roast might be fork tender in half that time or less.   But that's usually a high price to pay for a quicker pot roast.  And many people would prefer to make rarer "prime rib" or steaks instead with that cut.

If you are in the US and are looking at graded meat, it's also important to take into account that the USDA grading system is designed to tell which carcasses produce the most tender steaks.  For most meat you see a grocery store, grading will only represent degree of marbling (which adds both tenderness and flavor when cooking fast).  The grading is NOT designed for evaluating tougher cuts that will be cooked for long periods.  Someone in my family was once convinced at a high-end butcher shop to buy a "Prime" chuck roast at close to three times the cost of a "normal" chuck roast.  The quantity of fat within this roast was incredible.  It was bought to become a pot roast, and after many hours in a slow-cooker, it had shrunk to less than 1/3 of its original size, sitting in a giant pool of liquid fat.  (In fact, there was so much fat left that I siphoned it off and used it for multiple batches of tortillas.)
Bottom line: the USDA grading system tells you nothing about "quality" for a slow-cooker.  Again, most people use slow cooking methods to cook cheap cuts, and lower grades are often fine for this purpose.
Comment: I am very tempted to give you the bounty, as it is so well-thought out and presented. But I am highly skeptical that a cut with minimal amounts of connective tissue (like filet mignon) will taste good after many hours at a simmering temperature. Both my experience and the books I have say it will be tough. And even though many things in cooking are a matter of taste, I have never met someone who liked tough meat. So I'll go with the conventional wisdom in Debbie's answer. But I wish this answer would get more upvotes than just mine, it deserves them.
Comment: @rumtscho - I wasn't after the bounty; just trying to provide some other info. I've never cooked a whole tenderloin or hunk of filet this way, and I think it would be a terrible waste of an expensive cut - mainly because it would be incredibly bland and would be too easy to "dry out", not because it would be tough. It also goes against my primary advice, which is to buy "cheap." Can you point me to a source that says filet cooked for many hours will remain tough? (I did once use it as large stew meat chunks when I had extra; it certainly wasn't tough, but it was rather bland.)


What lens should I buy to get better pictures of a one-year old running around a dimly-lit house?

Question: I'm an amateur photographer with a Canon Rebel XS, and I'm trying to figure out what type of lens I should buy to take better photos of my one year old when she is running around in our dimly lit house. I seem to find myself in a lot of situations where there are kids on the move in low light, and my 50mm f/1.8 II just isn't able to do it.  Suggestions?
Comment: I hear you completely.  Another couple of questions on this topic are:  [how can I get good pictures of a fast-moving child without high fps](http://photo.stackexchange.com/questions/16247/how-can-i-get-good-pictures-of-a-fast-moving-child-without-high-fps) or [how to keep flash from disrupting scene](http://photo.stackexchange.com/questions/15965/how-to-keep-flash-from-disrupting-the-scene).  My own personal answer has been mostly to "pray and spray" with the 50 f/1.8, often at ISO 1600, but I'm also trying to bounce the flash off the ceiling more.
Answer: I don't think another lens is necessarily what you need, although since 50mm is a bit narrow indoors on a Rebel XS, you may want to consider something a bit wider. (The question Will a 35mm lens work for great indoor pictures of my kids? asks about Nikon but the answers will apply in general.) A Rebel-series camera has a sensor which is about 22mm wide, which means that the 50mm lens you have acts as a short telephoto. This is great for portraits of stationary subjects, but not so good for fast-moving small children indoors.
Something in the 28mm to 35mm range will be more "normal", a length which gives a convenient, natural perspective in many different circumstances. If you're feeling like it's often difficult to get everything you want in the frame with your current lens, this is something to explore.
For the low-light issue, though, the f/1.8 maximum aperture of your current lens is quite good. You can't go much faster without spending a ton of money. Image stabilization might help if your problem is that you can't stay still enough for longer shutter speeds, but I'm guessing the main problem with movement is in your subject, and nothing in the lens can help that. In fact, a fast lens (one with a wide aperture, like yours) is actually harder to use in this case, since your little one is apt to zoom right out of the narrow area of focus.
So, I think the main thing you need is more light. Since you probably don't want to add stadium floodlights to your house, take a look at Prime lens or flash: which upgrade will most improve baby photos? — with a focus on the "flash" aspect.  A better flash provide a lot more illumination than the pop-up flash does, and more importantly, will allow you to bounce light off the ceiling, not just flash it forward, avoiding the harsh light and shadows often associated with amateur flash photography.
Canon's lower-mid-range flash, the Speedlite 430EX II, is a little pricey at $300 — but that's less than a nice lens might cost. It's also very well featured and able to grow with you as you upgrade the rest of your photography. You could also choose a compatible third-party option like the Metz 50 AF-1 ($200) or the more basic (all-automatic only) but very powerful Sigma EF610 DG ST ($150). Or, you can get a much-cheaper all-manual Yongnuo YN-560 ($70!), but that may not be what you want for in-the-moment kid photos.
Comment: _"In fact, a fast lens (one with a wide aperture, like yours) is actually harder to use in this case, since your little one is apt to zoom right out of the narrow area of focus."_ -- it's hard to overstate this.  My mother would tell pictures of having the nose in focus and the ears out-of-focus, but until I had my own toddler (and camera), I didn't really appreciate this.  At f/1.8, you can't even rely on framing by focusing with the center point & repositioning, since even that much movement can change what's in focus.
Comment: "little one is apt to zoom" pun intended?! Hahah!
Comment: Thanks for the ideas, I think I might go for the flash rather than a new lens.  I didn't really consider this because I hate the way the built in flash looks and I normally opt for natural light if at all possible, even if it means boosting my ISO to 1600 and using the 1.8 aperture setting.  I'm guessing that the flash you recommended is fast (being called the "Speedlite" and all).  The slowness of the built in flash and the distraction the strobe causes often ruins the moment.  Have you found this to be an issue with the external?
Answer: Creating Memories
I think that what you're trying to do is capture memorable images of your daughter.  (Correct me if I'm wrong!). I don't think you're aiming for photographic perfection.
As a result, many compromises - which may sound technically iffy - are fine for this kind of photography.
Bearing that in mind here are a few suggestions...
Don't be afraid to bump up the ISO
Even if the result is very noisy, if you get "the" shot, then nobody will notice the noise.
Slow down the subject
This works differently with different children, but giving them a toy (especially a cute, cuddly, photogenic toy) might make her stop moving for several seconds (!) - enough time for you to snap off a shot.  The trick is not to let her see it until you give it to her.  You could have a helper do this.
You could place a big cushion in her path and lie in wait. Negotiating the obstacle will present some interesting shots.
When you have no light, any light is good light!
Get a work lamp and put it in the room. I would point it at the ceiling to get good diffused / spread out light.
Set an appropriate white-balance (or shoot in raw).
Also, consider using the pop-up flash on your camera - perhaps dialled down (set the flash exposure compensation to -1 or even -1.5 stops).
Comment: +1 for **creating (and capturing) memories** rather than technical perfection.
Comment: Thanks for the suggestions!  I've employed these strategies to some success, but I still feel like I'm limited in what I can capture with this lens. I've tried using the highest ISO (1600) along with the 1.8 aperture, but even then I'm often unable to get enough light to produce a fast enough shutter speed for a nice looking photo.  I can capture the moment to some degree, but I'd love to have a better quality photo instead of one with some features out of focus or blurred.
Comment: @MichaelKjörling:  Agree. Or, at least my wife would agree, and I struggle with it.  ;-)
Comment: Well, @Meghan, then you just need to get some more light in there - strobes or something.  To quote Scotty: Ye canna change the laws of physics!  Good luck :)
Answer: Having a good lens is important for indoor shots: I recently reviewed a 35mm lens that I use with my Nikon Camera;
http://www.amazon.com/review/R30I905GN3RLGM/ref=cm_cr_rdp_perm
I would think a good 35mm lens for a Canon would produce similar results. It is also important to ensure that the ISO setting is appropriate for the light setting. Some people avoid ISO settings above say 600 because the image can get "noisy". However, modern cameras are better and I find I can get quite a good shot at ISO 1000+. It's important to experiment at different settings (ISO, f stop and shutter speed) to get a feel for the quality of images your camera can produce.
Comment: Hi Denys! This comes across as a little promotional, with the link to your off-site review. And I'm not sure it really directly answers the question, especially as Meghan mentions that she already has lens of equivalent speed; can you comment on that? And since she mentions that she's not happy with the results, why assume that she hasn't experimented with different settings?
Comment: Good points; I am not trying to promote the 35mm Nikon, just show I have had some experience with it. Although the 50mn canon lens stops down to f/1.8 there could still be differences in performance between what I was assuming was a "lens that comes with the camera" and a prime lens.
However my main point was to note the importance of ISO in low light photography. No one appears to have mentioned this so far. I assumed that if Meghan had tested different ISO settings, etc., with the lens she would have mentioned this.
Apologies if I have made too many assumptions!
Comment: Thanks for the clarifications, and welcome to Photo Stack Exchange!
Comment: I think I've maxed out the capabilities of my lens and camera and I'm ready for an upgrade!  Thanks though.
Answer: Your lens is fine, what's missing is light. That means a flash, increasing light conditions in your house by turning on some lights, and/or increasing the EI of your camera.
Do not make the (very common, sadly) mistake that everything is to be solved by adding more gear to your kit.
Comment: Yes, I agree light is an issue. It seems to be an issue pretty frequently though, and I can't always add more light when I'm taking photos at other people's houses. My in laws have a really dark house and that is the main place I'm taking photos of my daughter and her cousins.  Christmas, Thanksgiving, and birthday photos come out less than perfect, and I'd like to improve what I can do with my equipment rather than moving lamps around at their house.  Thanks for the input though.


What happens to a person who consumes spoiled food?

Question: I'm asking specifically in the cases of meat and milk. Is the worst case simply an upset stomach?
Comment: It really depends on the spoilage.  Could be anything from botulism to vomiting.  Should I answer, or is the question too broad?
Comment: @can-ned_food It seems too broad to me, but if you think you can master a good answer go for it.
Comment: DaveL:  A)  Why do you ask?  B)  Why meat and milk specifically?  C)  Do you only want to know what's the severest that can happen?  Or do you want to know both the lightest and severest?
Comment: At the time of my asking, I was concerned about meat/milk specifically, because it seemed to be like proteins would go bad more quickly than carbohydrates, but I wasn't sure. I wanted to ask because I wanted to know about the range of possible consequences, depending on how severe the spoilage.
Answer: The worst case scenario is death from complications due to bacterial food poisoning. The specific species' will vary by location. Here in the UK, food poisoning from meat and dairy products are most commonly due to Enterobacteriaceae (esp E coli),
Campylobacter and Salmonella. Common symptoms include diarrhoea, vomiting, stomach cramps, elevated temperature, which if left untreated may lead to death due to organ failure from dehydration.
Note that eating spoiled food has the potential to cause illness, but may not do so. There is no way to know in advance. Also note that the species of bacteria that cause illness are often not the ones which cause products to be noticeably spoiled. Thus it it is possible to consume (visibly/smellably spoiled) food such as dairy (spoiled due to lactic acid produced by Lactobaccilus) but it is unikely that lactic acid or its by-products will make you sick (Lactobaccilus is included in many "probiotics")
Sources:
Borch, Elisabeth, Marie-Louise Kant-Muermans, and Ylva Blixt. "Bacterial spoilage of meat and cured meat products." International journal of food microbiology 33.1 (1996): 103-120
https://www.ncbi.nlm.nih.gov/pubmed/8913812


SE Photography Redesign

Question: I don't know if this is the right place or way to post this, but I wonder if there's anything to proposing a redesign for this site. It's very functional (like all SE sites), but it's hardly had any polish added to it since it was originally designed in 2010. Not to say that it's poorly designed or anything, I've just seen some of the new sites (like gd.se, AskDifferent and work.se) they've got very clean, bright and fresh designs that would be great to see over here too. I apologize if this inappropriate, but I couldn't help but atleast raise the question.
Answer: We're actually in the process of converting existing graduated SE sites to a new LESS(CSS) set up. While we're doing that, we've been giving some older sites some design updates, as well as retina support(svg) for site logos and icons. I'd love to hear some feedback from this community about new design direction. I still love the weekly community photo feature in the header. As for as the main site design goes, I'm definitely open to update logo, and overall look and feel. As for Meta, making it a dark theme was the biggest mistake I made.
Feel free to use this thread to submit design ideas.
Comment: FYI: "dark theme" doesn't mean "bright grey background". The background should be #000.
Answer: I agree, we should have a redesign. Our site was designed pretty simply and pretty quickly, without a lot of input from the membership. Personally, I've never cared much for how our meta came out, and overall I think our design could really use some spicing up. Our logo is too simple, I think, it doesn't really speak to photography, it feels more graphic-design like.
We have also had a number of funky issues with the "negative" nature of our meta site that makes soemthings show up incorrectly, difficult to read, etc. Some have been fixed, I don't know that all have.
I don't know how this is done on StackExchange, but a redesign of our site definitely gets my vote.
Comment: @MichaelT IMHO it would be confusing...but that may just be because I've only used a camera with a split prism once about 12 years ago.
Comment: A logo that was like a head on view of a camera, where the lens was the focal point would be quite eye catching...
Comment: Do I smell a logo design contest?
Comment: Do people still associate the split prism in the viewfinder with photography? Or would that confuse people who never touched a manual focus body?
Answer: Now, I'm actually indifferent to the layout of this site; however, I will ask this one question: why change it?
Are we wanting to change it just to change it, have we had a lot of people complain in meta or chat, or do we want to look closer every other SE site that has just updated?
Again, I'm indifferent on the current layout and I'd like to see some ideas before I say this is a good or bad, but I'd like to know why change it in the first place.

SE Photography Redesign


Was using the Force Projection ability responsible for what happened to Luke?

Question: I've seen some interesting posts regarding why Luke dies in Star Wars Episode VIII The Last Jedi, and also how Force Projection works and the similarities between Force Ghosts and Force Projection.  I was left very unsatisfied by Luke's death because the reason for it isn't apparent.  It's possible the strain of Force Projection is what killed him, but that reasoning doesn't sit well with me.  Maybe Force Projection is an ability gained by a Jedi Master after or during the transition to Force Ghost.  I prefer this idea, since it would mean Luke would have had to have had one foot on either side of Life and Death to pull it off, and certainly we know of no one who's returned to Life after gaining the abilities of a Force Ghost.
Comment: I read it as death after an enormous exertion.
Comment: @AbalogProphet I have a different viewpoint. What if much experience and skill level is required to even attempt Force Projection? Because even Luke Skywalker could only do it when he was old. Another point is what if this technique was forbidden and hidden for the very reason, given that Luke and the Jedi Council would have known how hard and dangerous it would be? I think it can be safely concluded that Luke knew that what he was attempting was a last resort.
Comment: I have several problems with that explanation.  From a story perspective, if death from extertion with the Force were possible, why haven't any Jedi died that way before?  Why aren't there stories of the many impetuous Padawans who burned themselves out doing something brave and/or stupid with the Force?  Not to mention, this tradeoff of life for power seems more a Sith thing to do than Jedi.  I can already hear people arguing 'But maybe it's a secret' and to that I say, 'How very *deus ex machina*.'  That may very well turn out to be the official explanation, but I really don't like it.
Comment: Yoda is distraught after lifting the X-wing out of the swamp, so yes, using the force can have physical manifestations.
Comment: He died because they couldn't decide which film they were making. Does Luke fight Kylo Ren in person, or via a projection? If he fights Kylo in person, does he lose? Does he die? Just do all of them! Luke fights Kylo, gets hit, but big surprise, he's not really there, and the swing hit nothing!  He survived!  And then he died!  For some reason!
Answer: Something to note is that the first time Kylo and Rey do their force communication thing, Kylo at first thinks Rey is using Force Projection but then he realizes she isn't when he says to himself "You're not doing this, the effort would kill you"
So to some extent early on in the movie they set up that Force Projection over long distances could be fatal.
Answer: That's not the first time we see this kind of death. The first time was Ben Kenobi during his fight against Vader (Star Wars IV: A New Hope), and Yoda after the Jedi training of Luke (Star Wars V: Empire Strikes Back). Both of these deaths seem to be on purpose or like an accomplishment(Ben's death to let Luke handle the suite and give him motivation? And Yoda's death because he finished training Luke)
We can see other kinds of death that are more "traditional" (without
the disappearing effect) in the different Star Wars movies (for example: Qui-Gon Jinn) but they don't seem as peaceful as the others I quoted.
So, I think the death of Luke was not due to the projection but because of his accomplishment in helping the Rebellion for the last time, like a redemption for his disappearence during the past 10 years (not sure of the time).
Answer:
Yes, it contributed, but it may be philosophically debatable what the IMPACT of "choosing" to die a particular way means for a Jedi...

"I don't want to get too explicit, because I like people being able to
  have their own interpretations. But I think definitely the act of what
  he does at the end literally just takes everything out of him. That's
  a huge thing. Also... he's having his final act be something of
  myth-making in a way."
Of course, we said "final scene" and not "death scene" because there's
  always the possibility that Luke could return as a Force ghost in
  Episode IX, which J.J. Abrams and Chris Terrio are now writing, with
  Abrams to direct. Johnson agreed that the son of Skywalker could
  indeed make an encore, saying Luke's ending in The Last Jedi "seems
  like it just gives you a whole other realm to get into if [Abrams and
  Terrio] chose to in the next film."
  http://www.syfy.com/syfywire/rian-johnson-what-really-happened-to-luke-last-jedi

Rian Johnson has said that Luke astral projecting did contribute in exhausting Luke, but clearly, given what we have seen before with older Jedi Masters (Obi-Wan, Yoda), Luke also "chose" to become one with the Force, given the way his body disappeared/dematerialized.

When other Jedi characters either do not choose to and/or are unprepared to die (Qui-Gon Jinn), their body is left behind and it may be harder for either their Force Ghost to come back and/or for other Jedi to communicate with them in the netherworld, as it appears to rely on several factors such as training and/or metaphysical geology in some cases.

"It is I, Qui-Gon Jinn."
  "That cannot be. Dead, you are."
  "No. I am part of the Living Force, Yoda."
―Jinn communes to Yoda during the Clone Wars
Revenge of the Sith - Transcript
YODA: Master Kenobi, wait a moment. In your solitude on Tatooine,
  training I have for you.
OBI-WAN: Training?
YODA: An old friend has learned the path to immortality. One who has returned from the netherworld of the Force. Your old master.
OBI-WAN: Qui-Gon?
YODA: How to commune with him, I will teach you.

Over the past few years, Star Wars "force ghost" mythology has expanded from the Prequels to Star Wars Rebels, to the new trilogy and so on.
One of the really cool advances and unique juxtapositions The Last Jedi added was show viewers an astral projecting Luke, who choses to die at the same time as NEARLY MATERIALIZED Force Ghost Yoda, along with the sudden departure of Snoke.
With Yoda's advancement, it becomes clear that Force Ghosts may be able to play much bigger roles than one may have previously thought; -now being able to more heavily interact in some [metaphysical] spaces!
But to further conclude, this advancement may mean it is not The Last Time one may see either Luke or Snoke (remember Snoke is NOT a Sith and it's unclear what his beliefs with the Force are or originate), let alone they may be able to more aptly pyschically interact with the other characters. Rey and Kylo Ren seem to be a part of some yet to be disclosed force mythology where each has some "raw" power that goes beyond traditional force sensitive beings, thus the stage is "ripe" for these particular dynamics to occur.
Comment: Also some trivia: TFA concept art reveals they were considering bringing back a kind of "struggling" Phantom-Ghost Anakin/Vader entity. So far it seems like they dropped that plot, as TLJ operates as a series of ruse and unclarity and comes off like a monkey wrench to what Abrams' TFA seemed to set up--including Kylo's obsession with Vader seemingly important, but the MYTHOLOGY of TLJ could still tie back to that in some way, when you think about these mythology choices.


How can I verify the Monero coin supply without using a block explorer?

Question: Is there a command I can give the Monero daemon to calculate the total of all coinbase transactions so far?
How do block explorers calculate the Monero coin supply and how can I verify their accuracy?
Answer: Starting with v0.10.1, there is now a command print_coinbase_tx_sum that give you this information.
Answer: There is no such command. However, it'd be easy to add. Feel free to add a request for this on https://github.com/monero-project/bitmonero/issues
Comment: https://github.com/monero-project/monero/pull/1204
Answer: This question has a fundamental misunderstanding of money supply and the link with coinbase transactions.
You would be right in a perfectly secure system, the coinbase transactions are the only way to add coins to the money supply.
The reality however is different. Bugs in the protocol (like the infamous keyimage bug that allowed the creation of infinite money) can create additional coins in the system.
Creating commands like print_coinbase_tx_sum may give you a good indication of the money supply but it should not be taken for facts.
Answer: You can print the total coin supply with the command print_coinbase_tx_sum
However, this assumes that there were no issues with transaction construction. In this case, the supply can be audited afterwards to see if there were any errors. Here is the information for a vulnerability that was found with Monero and patched before exploitation:

In Monero we've discovered and patched a critical bug that affects all CryptoNote-based cryptocurrencies, and allows for the creation of an unlimited number of coins in a way that is undetectable to an observer unless they know about the fatal flaw and can search for it.
We patched it quite some time ago, and confirmed that the Monero blockchain had NEVER been exploited using this, but until the hard fork that we had a few weeks ago we were unsure as to whether or not the entire network had updated.


If entities are all that IS [entities = being], isn't Heidegger's claim that being is something "extra" incongruent?

Question: I saw that there's already a question about this but the emphasis was on what could being be if not an entity. Heidegger thinks of Being as something "extra", a priori, to entities. I'd like to question the "need" to make such a differentiation between entity and being.
Comment: It is unclear what you are asking, I am afraid, incongruent with what? Late Heidegger's position was that the traditional Western metaphysics, starting with Plato and Aristotle, obscured the experience of being, and confused being with beings ("entities"). But he is not alone in criticizing metaphysics for loosing the sight of life under the play of abstractions, neglecting the practical, taking essence over existence, as Sartre put it. The issue is not specific to Heidegger's phrasing in terms of the meaning of being, the distinction between being and beings, etc.
Comment: I made an edit which you may roll back or continue editing. I am hoping that someone will be able to answer this. I am curious about it as well. Welcome.
Comment: Thank you for the edit - Replying to Conifold now: I thought the definition of entities (beings) was precisely to be (being). If Being, as per Heidegger, somewhat underlies entities, then what are entities?
Comment: Heidegger makes a distinction between individual entities and what they all have in common, or between 'beings' and Being. If we take away everything that makes a being discrete (qualities, attributes etc) then there is still something left over. Kant called this the thing-in-itself' and thought it was plural, Heidegger calls it Being and thought it was singular. Both place the reality of phenomena beyond the qualities that make it a distinct individual. A fundamental theory requires that this distinction be made.  .   ,  .
Comment: Yeah, I don't know how we can answer this question as worded. It's basically asking "if Heidegger is wrong and there's no Being, what's the point of talking about Being?" *answer: none.*
Answer: Heidegger makes a (difficult) distinction between 'beings' — entities that exist in the world, like tables, papayas, or wombats — and 'Being,' which is the activity of existing. This is a noun/verb distinction: just as you have 'runners' and 'running,' where the former are entities that are defined by the latter activity, so we have 'beings' that are entities defined by the activity of 'Being.' 'Being' is not itself an entity; it is the condition by which something is classified as an entity.
Being is not something extra to beings. Instead, beings are specific instantiations of the general principle of Being.
Heidegger makes this distinction because he wants to get at the nature of this activity of being-ness without getting bogged down in specific examples of being-ness (i.e., entities). In fact, Heidegger thinks that the focus on entities obscures the question of Being. If we look at a table, we tend to start at the premise "that table exists," and lose track of what Heidegger thinks is the important question: what activity is that table engaged in that means it exists? We need this conceptual division or we will collapse into a kind of reductionism (a mere list of particular beings, not an understanding of the nature of Being itself).


Salutations or greetings for the various Jewish holidays

Question: Is it right to, and is there a particular salutation for most of the major holidays in the Jewish calendar?
I have a couple of new friends who celebrate their Jewish faith, I was wondering if there was a generic salutation or specific salutations for the various holidays?
Specifically thinking about Shavuot, but was wondering in general too.
https://www.hebcal.com/holidays/2018
Comment: [Welcome to MiYodeya](https://judaism.meta.stackexchange.com/a/3887/11501) Gabriel. It is a perfectly fine question.
Comment: I hope this is an ok place to ask this kind of question :)
Answer: One traditional greeting for Jewish holidays is Chag sameach, meaning "a joyous holiday".
Some of the holidays have specific variations of the greeting, or specific greetings, e.g., taking your list in order

Pesach: Chag kasher vesameach (meaning a kosher and joyous holiday, a reference to the fact Jews don't eat leavened products on Pesach)
Tisha b'Av: due to the sad nature of the day, Jews do not greet each other on that day
Rosh Hashana: Shana tova (a good year)
Yom Kippur: Chatima tova (a good signature - as we hope to be inscribed in the book of the living for the year to come)

But you cannot go wrong with Chag sameach ! (except on Tisha b'Av as noted above)


Is there a service available to help continuously check for plagiarism online?

Question: We have a website with several thousand pages and it is frequently copied elsewhere; we'd like to know when and where this takes place to so we can make sure we are attributed correctly.
Answer: Plagiarism Today has a resource page with a bunch of tools for use in various contexts(feeds, images, etc.) The standard for text content for some time now seems to be Copyscape, and their Copysentry is a paid and automated service.
You should give that page a scan for some other techniques you'd probably want to consider.
Answer: FairShare offers a free service that tries to automatically detect where and when your content is being reused, based on an RSS feed you supply.
Supply your feed address in the first step, then choose "I don't license my content" in the second step (unless you want to license it for reuse):

Click the link they send you by email, and FairShare then publishes two RSS feeds that you can subscribe to containing sites reusing your content (one containing all examples of reuse separately and one with a weekly summary). They say that there can be a delay of 12 hours between a site reusing your content and them detecting it.
You could also include unique codes/keywords in your content and set up Google Alerts to detect them.
Comment: I tested fairshare but sadly it wasn't sensitive enough compared with copyscape. Copyscape came up with a number of sites that ripped us off, sadly fairshare came up with none.
Answer: You can also use Google Alerts to notify you whenever Google finds a page that contain you specify. In your case you would have Google look for unique text in your pages.


Best ways to get questions re-looked at?

Question: I recently looked at the questions I had asked earlier and found that they were worded improperly. So I reworded them the best I could. However I have found that when I reword a question (to improve it due to the fact that it isn't good) these questions aren't really re-looked at. So why do we tell users to fix existing posts if existing posts don't get re-looked at?
Comment: To get the obvious solution out of the way: Have you considered offering a bounty?
Comment: Exactly what I'm trying to figure out. Why is it if I went back and edited it so the question is more clear (it was interpreted in a different way then I ment it to be) how I have people re-look at it?
Comment: @DanielBeck No. The only question that is not answered I have already put a bounty on before. It did nothing.
Comment: Could you please provide examples? I have some difficulty finding the questions you're referring to. I only found [this](http://superuser.com/q/573277), and it was edited just 18 minutes ago. Its -4 score prevents it from showing up on the from page, and the `[closed]` and score are discouraging new views anyway.
Comment: Why can't I view [this](http://superuser.com/q/573277) question linked by @DanielBeck ?
Comment: @KevinFegan The question has been deleted by three users with [10k or more reputation](http://superuser.com/privileges/moderator-tools).
Answer: Generally speaking, editing older questions and posting bounties will get them looked at again. Edited questions appear on the front page again, they appear on /questions?sort=active, or, in the case of bounties, on the Featured tab. Making the question title clearer and using appropriate tags will get you more question views.
The improvements to the question, like making it clearer and providing more information, serve to improve the chances to get responses (answers or helpful comments) once someone clicks on the question.
All of this has been discussed before, for example here.
If this doesn't work, it doesn't mean that the advice to improve questions by editing is bad. It's just not a panacea. It generally helps, but there's no guarantee. Consider questions that too specialized to get answers on SU: No matter how well researched, clearly written, and well presented a question is, you won't get an answer.

In this specific case (I'm using the one question I found as reference here):

Its score is -4.
It's closed.

These issues make it much more difficult to get any regular user's attention: People mostly or exclusively using the front page will not get to see it due to its score, and in all other lists, the [closed] will serve to deter users from viewing the question again ("What's the point? I can't post an answer anyway.").

You edited it for the first and only time just two minutes before posting this meta question

Are you in a hurry? It often takes quite a lot longer for answers to appear. Please also consider the case that there might be no good solution within the boundaries you have established.

So... what can you do?
Getting the question reopened
General advice is here.
We have a re-open queue for regular users. Closed questions will not automatically appear there though: You need one person to actually vote to re-open, or make a significant edit to your post in order to improve it. Users with reopen privileges can then review your post.
Another option is to flag it for moderator attention. Explain what you changed and why you consider the close reason to now be no longer valid. Make an effort, don't just write "Reopen, it's no longer NARQ".
You could also ask in chat. It's similar to the above, explain that you've fixed the question, and would like them to take a look at it and up vote or vote to re-open (or alternatively explain why it's still not good enough).
Getting people to find it and view it
Getting rid of down votes is difficult if nobody's even accessing the question. And a negative score is a good way to prevent that. You could get additional views (and possibly up votes, leading to increased visibility) by posting a bounty.
Consider making the question title clearer and more specific to entice users to click on it when they see it listed somewhere. Right now, it doesn't explain what the question is about very well. "How should I deal with my pre-installed copy of Windows 8?" is very vague and explains nothing. The comments indicate that you're looking for a very specific kind of solution, so not why ask for it in the title?
If users left a comment on your question, and explained why they down voted or voted to close, and you addressed any issues in your edit, you could let them know that you fixed it. Be nice about it, and make sure you actually addressed what they wrote about. Don't just spam anyone who left a comment. If you're lucky, they'll revise their vote.
Comment: Hangon, there _is_ a reopen queue for regular users - http://superuser.com/review/reopen
Comment: Bringing up an improved question in chat can also help to revert a negative score.
Comment: @Sathya - it says ***"You need at least 3k reputation to review Reopen Votes. "***
Comment: @KevinFegan [It's tied to the close/reopen privilege](http://superuser.com/privileges/close-questions).
Comment: @DanielBeck - I guess I was confused when @(Sathya) said - *"there is a reopen queue for **regular users** - [superuser.com/review/reopen](http://superuser.com/review/reopen)"*. I didn't consider 3k+ users to be ***regular users*** - but I guess all things are relative.
Comment: @KevinFegan Understandable. But consider that something as common as the ability to [vote down](http://superuser.com/privileges/vote-down) is only available to the top ~15% of users on SU! And you neither need to be an employee of Stack Exchange, Inc., nor be an elected moderator for the higher privilege levels. They are automatically awarded once you reach the required reputation. Of course, reputation is used to limit the more powerful privileges to those that are hopefully experienced enough and familiar with site policy, but there are no special requirements besides that.
Comment: @DanielBeck - So, are you saying that 85% of users on SU have a rep of less than 125 (reputation required for priveledge to cast downvotes)? If so, then I'd guess only a very small percentage of users have a reputation of 3k+. I'd consider them something like ***Advanced users*** or ***Very Active users*** not regular users. Well in any case, I'd guess the facts are presented and we are just into semantics, and I didn't mean to turn this into a discussion.
Comment: @Kev By regular users, I meant users who aren't employees/Moderators, context being Daniel's first revision of the post which mentioned "_There's a page listing questions with re-open votes in the moderator tools, but it's only accessible for 10k+ rep users._"
Comment: @Sathya - got it, thanks.


Manual Mode : Dark picture even in broad daylight

Question: I am a new DSLR user. Whenever I click a picture using Manual mode the picture is pitch black. You cannot see anything. Which setting should I change? How can I overcome this problem? It's only like this in the manual mode.
Help!
Comment: Use search function on this site to find already posted questions and answers, like ["How do I know I have the correct exposure in manual mode?"](http://photo.stackexchange.com/q/9625/17441). I suggest to start with reading answers in ["How to start learning photography?"](http://photo.stackexchange.com/questions/5283/how-to-start-learning-photography)
Comment: Whats is the shutter speed and ISO rate? Pls be elaborate
Comment: Remove the lens cap?
Answer: There are 3 things that control how much light enters your camera: Aperture, Shutter Speed and ISO - to get a properly expose picture you need to balance those 3 with the amount of light you have.
If you are shooting outside in direct sunlight start with Aperture:f/8, Shutter Speed 1/400 and ISO 100 (those are middles-ish-of-the-road values chosen according to the "sunny 16 rule", there's nothing magical about them, they are just a sensible starting point to test if your camera is working).
The settings above should give you a close-enough exposure for subject in direct sunlight - if you use them you should see an image and not get black picture - if you still get a dark image slow down your shutter (for example to 1/200, then 1/100...), if the picture is too bright make it faster (1/800...).
After you see you can actually get an image learn how to use your camera's light meter - you should see inside the viewfinder a scale with an arrow, that arrow will tell you if the camera thinks you settings will make the image too bright or two dark - to get the what the camera thinks is a right exposure play with the aperture/shutter speed/ISO settings until the arrow is right in the middle pointing the the zero.
The whole purpose of manual mode is to let you override what the camera thinks is the right exposure, so you don't need to take every picture on the exact middle - but you need to be able to quickly and easily set the expose based on the meter before you can effectively override it.
Answer: Simple answer: don't use manual mode.
I think there's a prevailing attitude among some camera owners that if they're not in manual mode, they're not doing proper photography.  Some people seem to believe that professional photographers always shoot in full manual mode, even if they are taking snapshots of their daughter's friend's birthday party, for example.
Neither is true.  Manual mode is specifically helpful for when you want to be able to set a particular aperture and shutter speed.  If you are not in a specific situation where you want a specific aperture and shutter speed, you don't want manual mode.
When you shoot in full manual mode you are fully responsible for exposing the picture correctly: making it not too light or dark.  The camera will not help you at all.  If you shoot in manual mode but complain that the picture is too light or too dark, you are putting the cart before the horse: the whole point of manual mode is for when you know how to set the exposure better than the camera would if you let it choose them automatically.  Using manual mode should start with knowing what aperture and shutter speed will result in the desired exposure.
What's happening in your situation is that you are using full manual mode but have not taken the care to choose an aperture and shutter speed that would result in a correct exposure.
The long answer to this is to teach you all about aperture and shutter speed and how exposure is calculated.
But the more concise answer, in my opinion, is just to advise you to use auto mode.
Professional photographers venture away from auto mode because they want to achieve a specific effect by using a particular shutter speed or aperture (or both).  That is, they understand what effect a particular aperture or shutter speed has on a picture and want to exploit that.  It doesn't sound like you're in this position since you expected the camera to get the exposure right.
If you would like to learn more about the effects of aperture and shutter speed, by all means do so.  Also check out the Aperture-Priority and Shutter-Priority modes on your camera, as they allow you to have full control over just one of these settings at a time while the other one is adjusted automatically by the camera.


How can I safely clear the media cache on a production sitecore CD instance?

Question: I would like to manually clear the media cache on a production CD instance. Is there a way to clear the cache without causing disruption to the site?
Answer: Other option is to delete from time to time media cache using an schedule agent. Current value is 24 days but if you need to clear more ofen just decrease max age parameter of the last setting (see below settings). It is not recommended to clear media cache very often because you will have some performance impact.
<code>  <agent type="Sitecore.Tasks.CleanupAgent" method="Run" interval="01:00:00">
    <files hint="raw:AddCommand">
      <remove folder="$(dataFolder)/audit" pattern="audit.*.txt" maxCount="5" minAge="01:00:00" />
      <remove folder="$(dataFolder)/logs" pattern="log.*.txt" maxCount="5" minAge="01:00:00" />
      <remove folder="$(dataFolder)/viewstate" pattern="*.txt" maxAge="01:00:00" recursive="true" />
      <remove folder="/App_Data/MediaCache" pattern="*.*" maxAge="24.00:00:00" recursive="true" />
    </files>
  </agent>
</code>
Answer: It is completely safe to just delete the folder /App_data/MediaCache without causing disruption. The minute an image gets called up again, it will be cached again, so no worries about the functionality of your website. We make sure it get's cleaned up every week.
In addition you can set up a clean up job to do the work for you. Unfortunately the usage of /sitecore/admin/cache.aspx does not clear the mediacache for you.
If you have an high performance on your website and do not want to cache your media items at all, you can always set this up in the sitecore.config file
<code><!--  MEDIA - CACHE FOLDER
        The folder under which media files are cached by the system.
        Default value: /App_Data/MediaCache
  -->
<setting name="Media.CacheFolder" value="/App_Data/MediaCache" />
<!--  MEDIA - CACHING ENABLED
        Indicates if caching of media files is enabled.
        Default value: true
  -->
<setting name="Media.CachingEnabled" value="false" />
</code>
In addition, you can use an orchestration tool like puppet to periodically clean up your cache folder based on the timestamp of the files, this way, you don't have to worry about your cached items as they will be cleaned up automatically.
Answer: I have just manually deleted the folders under App_Data/MediaCache/[site name] on each CD server. Never seems to have caused disruption since Sitecore will fetch the image from the database again if it does not find a cached version.
Answer: It shouldn't be a problem deleting it however, the initial load time for each page will increase as it needs to fetch the media items fresh from the server.
Usually not a best practice to delete ~/App_Data/MediaCache on the production server during business hours. I would recommend lowering the maxAge in the clean up agent as mentioned above.