I deleted every single photo from my iPhone (after backing up on computer), including both camera roll and photostream (I disabled photostream afterwards). For some reason it’s still showing 1GB of “camera roll” in settings -> general -> usage -> photos. When I connect it to iTunes, it shows something weird like “189mb” of photos. Anyone know what’s causing this and how to fix it? Even if there are still photos in some apps shouldn’t these be in the “documents and data” category not photos?
Assuming you have IOS 8.x…
Go to Photos -> Albums -> recently deleted.
Tap on Select (upper right) then “Delete All” lower left. That should do it. My experience is that the space used will take a while to update to reflect the removed images.