A wide-angle and a telephoto lens both are rated as f/4?

2 ⤊

A wide-angle and a telephoto lens both are rated as f/4?

a- both have the same diameter
b- the wide-angle lens has the smaller diameter
c- the wide- angle lens has the larger diameter
d-any of the above, depending on the ratio of the focal lengths of the lenses

2007-02-07 01:37:41 · 2 answers · asked by Jac A 1 in Science & Mathematics ➔ Physics

2 answers

The f/number of a lens is given by the focal length of the lens divided by its aperture. So, as a wide-angle lens has a short focal length and a telephoto lens a long focal length, for the same f/number the wide-angle lens must have a smaller diameter.

Examples: a 28mm f/4 wide-angle lens has a maximum diameter of 7mm; a 200mm f/4 telephoto lens has a maximum diameter of 50mm.

2007-02-07 02:12:26 · answer #1 · answered by JJ 7 · 2⤊ 0⤋

2007-02-07 02:46:24 · answer #2 · answered by Studly Jim 3 · 0⤊ 0⤋