When taking a macro picture the lens is usually very close to the subject. In some cases less then an Inch. Depth of Field (DOF) can be as shallow as two or three millimeters. The Auto-focus mechanism can not always detect what is most important to you in a macro shot – if it is not the center, you are better off making the decision yourself.
The more expensive your camera body is the faster is the AF sensor it has. If you have a fast lens, your autofocus will be even faster. But even the fastest focus engine can not always compete with fast action shots.
Sometime auto focus is not really an option at all. if you want to benefit some of the fine old lenses, you may find that they do not have auto focus capability at all or that they are not compatible with your SLR autofocus system.
For example, if you want to use the razor Nikkor 28mm f/2.8 lens you have no choice – you must go manual.
It is hard for the autofocus sensor to focus in low light. Even fast lenses with wide apertures can have a hard time in a dark room like a church or a cave.
Sometimes you want to have some artistic control over in a particular picture and create a blur effect for artistic reasons.
You may want to have the entire picture out of focus or have a negligible, almost off the frame object, in focus. In either case, moat auto focus mechanism will not allow you to perform the first and will give you a hard time achieving the second.
Have you ever wondered how the take those stunning nature shots that have both the nice rocks at the close front and the water fall at the far back sharp. Hyper Focal Distance is a photography term used to note the point that if you set your focus to it, you will gain the most Depth of Field front to back.
Jeff from has a great Hyper Focal Distance tutorial, which is recommended both for the technical enthusiastic and starting nature photographer.
When taking a panning picture, you have to follow a moving subject. One way to deal with the movement is to set your focus mode to AF-C (continuous auto focus), another is to rapidly half-press the shutter release.
Lensbabies are lots of fun. they give a nice shallow focus effect.
Lensbabies do that by having a flexible mount which imitates tilt/shift lens.
Just like old lenses, Lensbabies are manual focus only. On the other hand, this is just what you’d expect from a lens baby – you make the artistic call, including setting the focus point.
When Stitching a panorama it is important that all the pictures in the panorama will have the same parameters. Of course this include focal length and zoom; but you also need to place the following settings on manual: White balance; aperture, shutter, ISO and exposure in general.