I understand that the simple idea that f-stop is focal length divided by aperture really applies to a simple single-glass lens, not the compound lens systems used to provide good image quality in ...
This widely praised Nikon 105mm macro lens has a maximum f-stop value of 2.8. I've held it in my hands, it's a big lens. Meanwhile, this 50mm Nikon lens can go up to f/1.2, despite being 25% cheaper ...
I've heard that focal length of some lenses will become noticeably longer when focusing to a close distance, an effect called "focus breathing". Since f-number is focal length divided by diameter of ...