Why are some lenses larger, or smaller, on the objective end? Obviously, they all have to be the same size on the connecting end, but does a larger objective allow more light? Yet, a 52mm and a 72mm can share the same 3.5 or 2.8.
My 18-55 is 52mm; my 55-200 is 52mm; my 35mm prime is 52mm; my...