iPhone 5 says photo library is 7.1 GB but isn't and Storage Full prompt is shown My iPhone 5 tells me my photo library has 7.1 GB but in actuality it doesn't just 50 pictures. Can someone explain why I'm getting the "storage full" prompt?

Apps take up very little room and I deleted all videos and most pictures on my phone. Is there a cache that's taking up space?

Photo Library appears to be the culprit-files don't seem to be deleting though they don't show up.
Go into Photos > Albums > recently deleted.  Check that isn't full of pictures. You can delete them from there to permanently purge them.