Mathematically speaking the paper is correct. I think it actually depends what you define as "pixel". Sure, the pixel on your screen emits light on a tiny squa

Mathematically speaking the paper is correct. I think it actually depends what you define as "pixel". Sure, the pixel on your screen emits light on a tiny square into space. And sure, a sensor pixel measures the intensity on a tiny square. But let's say I calculate something like: # samples from 0, 0.1, ..., 1 x = range(0, 1, 11) # evaluate the sin function at each point y = sin.(x) Then each pixel (or entry in the array) is not a tiny square. It represents the value of sin at this specific location. A real pixelated detector would have integrated sin from `y[u] = int_{u}^{u + 0.1} sin(x) dx` which is entirely different from the point wise evaluation before. So for me that's the main difference to understand.