Image data takes on noise/damage when it's compressed, during things like saving and uploading to the web. When you turn that noise way up, it should be even overall. When it's wildly mismatched, it indicates pieces have been chopped in, like when a crappy voiceover has a word that's obviously wrong.

Note the sharp difference surrounding the in-focus drone's text, compared to the background drones, whose signs have a much higher level of consistency across the pages they're carrying.