Jay Bolton finds his iPhone, with 700 or so photos, has filled up its memory. He wonders after trashing other images why he’s still got a full phone, and doesn’t want to turn to iCloud Photo Library to help.
I’ve seen many times that iOS devices will retain as much as gigabytes of old items—especially in the Messages app—that it doesn’t purge when it’s no longer needed locally or has been deleted. The only way to restore this missing storage is perform a backup and restore, which wipes the phone. This dumps allocated but unneeded files, though it’s a time sink. (Apple’s guide will walk you through it.)
Read more here:: How to delete images from Photos