You may have seen this illusion. Look at it close-up, and it is Albert Einstein. Back away a few feet and it is Marilyn Monroe. What is going on here? You’re seeing the effects of frequency resolution.
Close-up, you’re seeing the finer detail that is familiar to you as details of Einstein’s face. When you back away, (or perhaps, remove your glasses) that fine detail becomes lost to you in the distance, only to be replaced by the softer, less detailed information of Marilyn’s face.