Changing the f-number of a camera by three stops by going from f/11 to f/32 will change the intensity of the light hitting the film by a factor of
A)8.
B)4.
C)1/4.
D)1/8.
E)32.

Question

Changing the f-number of a camera by three stops by going from f/11 to f/32 will change the intensity of the light hitting the film by a factor of
A)8.
B)4.
C)1/4.
D)1/8.
E)​32.

Quizplus · Accepted Answer

Changing the f-number by three stops means reducing the amount of light entering the camera by a factor of 2 for each stop. Going from f/11 to f/16 is one stop, then f/16 to f/22 is another stop, and finally f/22 to f/32 is the third stop. Therefore, the amount of light hitting the film is reduced by a factor of 2 x 2 x 2 = 8. So, the correct option is (D) 1/8.

Changing the F-Number of a Camera by Three Stops by Going