Are the locations of the circles of confusion found purely computationally? Do they have anything to do with the physical properties of the lens?
I think it probably have to do with both. In the calculation we did in the later slides, we are assuming the ideal thin lens situation where all lights converges without aberration. Yet, in real life we have compound lens that will make things more complicated. As for circle of confusion, it will influence the distance between the lens and the image. I tend to think it will be rather hard to compute accurately empirically.