eli5 / why are zoomed lights in movies composed of octagons?

Question

I mean..in movies when there are a lot zoomed lights, like car lights, street lights or similar they all looks like octagons. Do you know why?

In: 1

Answer 1

It’s because of the shape of the aperture blades in the lens different lenses can have different amounts of blades which changes the bokeh.

For fun you can put paper with shapes cut out over a lens to make different shapes in the out of focus lights.