What is it about a particular lens that makes it more or less contrasty? From a rudimentary scientific standpoint this doesn't make any sense to me. I mean if the optical quality of a set of glass elements was to somehow let through more or less light then of course this would be similar to closing down or opening up your aperture, but how can there be characteristics in glass that yield differences in contrast? The only way I see that this could be possible is for the transmission characteristics of the lens to be different for very bright light sources vs. very low or dark light sources. What am I missing?