Where
exactly are your photos now?
Do you have iCloud Photos enabled? (Settings>Photos>iCloud Photos>ON or OFF?)
- If you're using iCloud Photos, not a problem. Just restore your iPhone as new and your photos will be available from your iCloud account. Photos are not part of your backup and they don't need to be, since they're in iCloud.
If you're
not using iCloud Photos, that means that you have photos save on your iPhone in Camera Roll, and possibly "My Photo Stream" (if enabled).
- Camera Roll is not a problem either since it is part of your backup (whether you backup to iTunes or iCloud).
- But "My Photo Stream" is deceiving ... in iCloud only the last 30 days' worth of photos are in My Photo Stream, but on your iPhone that copy of My Photo Stream may have many more photos than the last 30 days. But the devious part is that My Photo Stream is not backed up, so if you restore your backup the only thing that you get back in My Photo Stream is the last 30 days' worth of photos.
So before you proceed, know where your photos are being kept.