Currently I have the Photos Library ("Photos Library.photoslibrary") in a directory that I back up. The library is about 14.5 gigs large. I use the iCloud Photo Library so that all my pictures are available across all my devices. As far as I know that library is dynamic, meaning it changes in size depending on how much space is available on my computer. So is there any point in backing up the "Photos Library.photoslibrary" file? How does that file work if it changes in size depending on the computer managing it?