When you edit a photo, iPhoto automatically creates a copy, and that’s what you edit. Any photos you edit, even if all you do is add captions or rotate the photos, are automatically placed in a tan Edited album in your iPhoto library. iPhoto saves your edits for you automatically, and you can roll back individual edits.
When you look at an edited photo in Photo, you notice a small toolbox overlay on the thumbnail in the photo grid to remind you that you’ve edited that image.
The photos in your Photo Stream on an iOS device are not in full resolution. Before you edit a Photo Stream photo, sync via iTunes and add the photo to an album so that the full resolution version is transferred.
When you edit a synced photo ...