Most of you probably know that JPEG is lossy compression method, meaning compression permanently throws out data and detail. Luckily, a typical compression can save 10 times the space of an uncompressed image without sacrificing much noticeable quality. However, if the image is repeatedly compressed and saved, artifacts introduced during compression become more and more obvious.
Reddit member Grundle decided to see what repeated compression looks like by saving the same image over itself 500 times at high quality (10/12 in Photoshop). He then combined the images into the following video:
I think it’s pretty clear why you should always work with RAW files if you care about the quality and longevity of your work. Every time you save those JPEG photographs, you lose a little piece of awesomeness.