Deleted all photos/apps on iPhone 4s but settings shows 3.1 GB of photo storage used
This may have been caused by a bug in iOS 8. I had the same problem and just now solved it by doing the following:


Go to Settings, then General, then Date &amp; Time.


Untoggle "Set Automatically". (We'll toggle it on again in the end.)
Set the time several months back in time. I set it a year back.
Go to the Photos app. The Recently Deleted album will still say that it has 0 photos, but if you actually open it, you may see that there are actually many in there! You can then click "delete all" and you will have cleared up that space.
You can now go to Usage in settings to see that space has been cleared up. If there is still some, try setting the time back and forward and see if you discover more photos in the Recently Deleted album.



That worked for me. I cleared up 8GB of "deleted" hidden photos.