As I was doing my reverse engineering of the lighting for this question, I wondered whether there's any discernable difference between a large light modifier far away versus a small light modifier close up. (This is outside the obvious things like required flash power.)
Previously, my understanding was that, all other things being equal, the factors that produce the same apparent size & light intensity were completely interchangeable. I'm wondering now if that's actually the case.
I'm thinking specifically about light falloff, due to the inverse square law. I wondered if the light from a close source might fall off faster (ie: go from bright to dark in a shorter distance) because the distance to the source itself is closer. Given a certain distance lit (such as the model's face), the ratio between it and the distance to the light source is going to be much higher for a close source than a far one... so it might make the falloff more pronounced. But I'm not sure of this by any means.
Is this correct? Are there other factors to that change based on apparent size?