when I clicked on my photos icon today a dialogue box popped up that i don't have enough storage on this device, would i like to optimize? or something like that. I clicked optimize (even though I didn't reall know what it meant) and now when I'm in photos and I click on a photo, a little circle appears in the bottom right hand corner of the picture and dials open to look like a pacman - I'm assuming its a clock but what for?
I believe that when you "optimised" your photos, you have uploaded them to your iCloud account, and what you have now on the device is a low resolution copy and so has saved some storage space on your device. When you click on it, it re-downloads the original from iCloud, and the pacman you see is the indicator that the original is being downloaded.