system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are camera lenses round, but the photos that they produce are square/rectangular?
gpt
Making round lenses is easier than square or other shapes.

The thing that actually captures the image (whether its the CMOS/CCD in a digitial camera or a piece of film) is still square or rectangular - the size of the optics are chosen to be just larger than the extents of the film frame/sensor - thats why on some viewfinders you actually have a rectangle (especially if you see a movie camera) - thats showing the cameraman/photographer what part of his view he will be capturing on fim/digital.