system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why are camera lenses always circular?
gpt
Camera lenses are not perfect. They don't focus all light colors the same way. You get tiny rainbow effects on your photo.

The further from the center light goes through, the bigger the flaws. A circle is the ~~optional~~optimal shape with no corner outlier points further away from the center.

Google Chromatic Aberration and look at images to see examples of what happens at the edge of a lense.