Originally posted by Firebird Let me ask the question another way.
Do all lenses at f3.5 allow the same amount of ligth? For example would a 40mm and 70mm allow the same amount of light at f3.5? Or does the 40mm allow more light because of the bigger angle of view?
The same in theory, in practice, it can differ. A simple Tessar design with 4 elements will probably pass more light than a complex zoom with 15 or more elements even if the aperture is identical.
A good low light lens will have a fast maximum aperture and will be reasonably sharp wide open.
There is no such thing as a good low light zoom lens.