On a sensor with infinite dimension you would always see 180 degrees. You can use the custom size here, https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/#{%22c%22:[{%22av%22:%228%22,%22fl%22:20,%22d%22:3048,%22cm%22:%220%22}],%22m%22:0}
As you shrink the sensor you can design without having to accommodate the 180view in front of the lens where the angle viewed is limited by the medium size. You just can't take that area and refocus it on the part you do see because it is a different view than what you want to capture.

That sounds like it makes sense, but I confess I didn't quite understand what you were saying.

[reh321]

And, by the way, @reh321, it still boggles my mind that there could be "retired software engineers" in the world, I still think that the transistor radio is a great

I was educated by the people who invented the field …… but that was fifty years ago.
I had to learn things as they came into being …. but that was forty or fifty years ago.