Precision seems to be a very important aspect of photography, so why are we able to approximate like this? A previous slide said that a real lens does not follow this rule; is there some reason why we can apply it anyway, or do adjustments need to be made to account for reality?
I think we can use this approximation in our calculations and from a rendering perspective, but in actual photography the real properties of the lens matter a lot more. Another issue is that the inconsistencies in a lens from manufacturing aren't something that can really be calculated, so there's no way to account for that.
How close to this ideal setting do real lenses usually get? Also, is it more problematic if the focal point is too far forward/backward or if the focal point is not centered behind the middle of the lens?