Comment by echoangle

It’s a single value, but it’s an integral over the square, not a point sample. If a shine a perfectly focused laser very close to the corner of one sensor pixel, I’ll still get a brightness value for the pixel. If it were a point sample, only the brightness at a single point would give an output.

And depending on your application, you absolutely need to account for sensor properties like pixel pitch and color filter array. It affects moire pattern behavior and creates some artifacts.

I’m not saying you can’t think of a pixel as a point sample, but correcting other people who say it’s a little square is just wrong.