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 called “bokeh” and occurs for things that are out of focus (usually implying a short-depth-of-field lens, low f-number, usually a lens that’s physically big compared to the sensor – and they use huge lenses in film-production).

The shape of the bokeh effect depends on the shape of the aperture in the camera.