well when u plug ur iphone in. Itunes will pop open. go to the devices tab and click on ur iphone. then after ur there. go to the photo's tab. now its up to you to select what u want to unsync. now ur phone will not auto sync all photo's from the selected folder. next if the space is still high it might be pictures and videos taken with the camera. u will now have to also manually delte these with ur phone.
best answer if i am right plz.