>Or to simplify (for the non-math majors out there like me > )... the aperture is equal to the diameter of the lens >opening divided into the focal length. 25mm lens opening on a >50mm lens equals f/2.0 (50/25 = 2). >Al
Aha! A bonus answer here. I recently purchased some used stuff in order to get a 300mm lens. With it came a very used F3, and several other lenses, including a very used 28-85 macro. This lens is a 62mm piece, which got me to wondering if there was (in general terms) any inherent difference in the larger diameter. The seller clearly used this lens on the body most of the time.
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? And does that make it 'better' in terms of light admission?
The bonus for me was to suddenly understand the f stop numbers. While knowing how they affect a shot, I never got beyond them as a theoretical number. Thanks.