system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why can't you smile in your passport photo?
gpt
Go to a mirror and smile normally. Now smile showing teeth. Now smile absurdly wide. Now smirk. Facial expressions can seriously change the general shape and outline of your features. The goal of a passport photo is to be as easily identified as possible... so removing all variables of expression gives you a clear baseline of what the person's face looks like.