Picture gets black and cant get them back

I'm sad to inform that the file that contains those pictures are most likely corrupted. A restore and backup of the OS will not bring them back.

This usually happens if photos are stored for a long time and the camera roll gets too big. Over 1,000 photos has been known to be risky though the newer iOS versions have been better at file management. I would recommend to sync regularly and remove your photos from the phone to a computer.

In hopes of recovering the pictures affected, you will need special software that can recover lost photos like they have for damaged SD cards. Though I cannot think of one in particular you may use on the iPhone.

Hope this helps and good luck,

Danny.