It is common for digital images to be saved repeatedly as work on an image progresses. Example shows progressive data-loss, color shift (red turns brown, white gets contaminated with artifacts), and edge-fuzzing after repeated saves.
Saved at PNG for best side-by-side comparison clarity --if browser doesn't permit inline looking at PNG filetypes, go to JPG below. (Oops, image at bottom row center should say "15" )
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this lesson inspired by this fb thread: