Photos taking up storage on iPhone when I have no photos

There might be phantom photos still in your Photos app. Just do these things and it will solve your problem.

1. Go to Settings
2. Date & Time
3. Untoggle "Set Automatically"
4. Manually change the date back. For example, today is December 10, 2016, choose something ex: like March 21, 2015. (You can change it back once we're done)
5. Close out of that
6. Open "Photos"
7. Select "Albums" you had already cleared out everything from the Camera Roll and "Recently Deleted" folder, But now you'll see that your "Recently Deleted" folder now has thousands of images back. Those are your phantom photos
8. Open it, "Select" and start deleting
9. Now, go back into Settings - General - Usage - Storage - Manage Storage - and you'll notice your Photo & Camera is empty if you deleted everything.

I had the same issue and no date/time tricks or whatever I found on the Internet worked for me. I managed to finally find and remove the photos using iExplorer application. Here is the youtube video. The app is not free but you can run it in demo mode and still find and remove the hidden photos.