>>So, it is then correct to say that a 52mm diameter 50mm >lens >>would have an actual smaller aperture than a 62mm >diameter >>50mm lens at any given f stop? > >No, that's not correct. As long as the front element is large >enough (in the case of a 50mm f/2 lens, it would have to be at >least 25mm diameter as explained above), the effective >aperture will not be affected by the physical lens diameter. > >>And does that make it 'better' in terms of light >admission? > >No. f/2 is f/2
Thanks Brian. After posting, I realized that the f number would be the same no matter the diameter. Then I just wondering about the second part, thinking that perhaps with larger diameter, at f2, the lens would be not as close to the edge, so maybe that mattered. Guess not. Oh well, it's fun to think about. For now will just go back to thinking that some lenses are 52 in diameter and some are 62 for reasons beyond my current understanding, and just enjoy shooting with them.