We are used to photos and images in a rectangle.

Why is that?

The eye actually sees things in a circle and two eyes see things in a funny fuzzy ellipse. But that is weird because it's a dynamic thing. The eye moves around the world focusing on different things. Just like you reading this and the other text is out of focus and blurry...yes, read it again and think about it.

But really, why do we put images as rectangles?

Is it because film was in sheets at one time...then rolls?

There is no reason we can't have circles or whatever shape.

but we stick with rectangles.

Our monitors and displays are rectangles. Movies are extreme rectangles.

Biology actually prefers the circle.

Your eye is a circle....ok it's a sphere, but the image is circular.

One might think because of this natural thing, that art esthetics might favor the circle. Does it? I'm not sure. Maybe the essence of art actually defies biology and challenges it.