Originally Posted by neuroanatomist
Well, that depends on how you define "light-gathering ability". If you mean "per area", then you're right. But if you look at "total" light gathering ability, then it's clear that full frame does have more.
Which definition you use will depend on what your purpose is. If you're advising a novice on how to get a good exposure in daylight, talking about per-area light makes more sense.
On the other hand, if you're trying to determine which camera+lens combination has the most light (and least amount of noise), then the amount of light per area is completely immaterial: all that matters is the total amount of light (and sensor technology).
For example, if you looked only at per-area light, it would dictate that f/2.8 on a digicam has more light (and therefore less noise, AOTBE) than f/5.6 on a DSLR. But in reality it does not, which is clear if you look at total light: an integration of light per area and total amount of area, where it is clear that f/5.6 on a DSLR has more light and less noise than f/2.8 on a digicam.
I'm sure you know all of this already, but I just wanted to point out that "per-area" is not the only valid way to interpret "light gathering ability".
Reply With Quote