Originally posted by mikeporterinmd A better way to think of this is that a longer lens hood could be used on a FF lens possibly yielding better results than the lens had on a FF when mounted on an APS/C. So, test it out with some black construction paper and tape!
Mike
Given that no one has provided credible images showing the shorter lens hood is inadequate it would seem unlikely that one could actually produce different results. This is one of those situations where I say "Stop speculating, show me some images that prove your speculation."
My guess is that in 100 trials you won't be able to find a single image where there is ghosting or flare using a lens hood that is shorter than it needs to be. You might be able to produce a few with no lens hood, on some lenses, because many lenses like my FA 50 macro and Sigma 24 macro, effectively have the lens hood built into the lens. So we aren't even talking all lenses here, we are talking only about lenses with protruding front elements, and not ones with recessed front elements.
But that's what we need to know with any of these hypothetical differences. Does the phenomena what ever it is happen often enough to warrant remedial action? Until you know that, further discussion is meaningless. You have to establish there is a real world problem, before you start remedial practices to solve the problem.
The biggest problem, again based on my experience with ghosting and flare, is the sun is in the frame. It has little to do with the size of lens hoods.