Perspective projection (or at least non-orthogonal) is by far the most common in photo-realistic graphics. When we use perspective projection, the (equally thick) slices of volume visualized by each pixel get larger with the distance. But with ray tracing we normally cast cylinder-like rays instead of cones. It seems to me that this must make quite a difference to the results: consider the two fields of view of pixels: cone-like one at the LHS, and cylinder-like one at the RHS, the pixels are at the bottom:
The colored lines here represent walls of randomly-distributed light sources with the same density in each wall. If we assume that the intensities of the light sources are the same, so that one of the pixels would "see" white average color, the other must necessarily have a color tint, because the left one samples more red compared to blue than the right one.
Am I right in this? If so, why does then ray tracing work? Why don't we do "frustum tracing" or "cone tracing" to get the colors/illuminances right? And if I'm wrong, then what is my mistake?