I take two pictures of my dog Kaycee.I use the same film and level of illumination for both pictures,but I triple the f-number for the second picture.By what factor will the required time of exposure change if the film is to receive the same total light energy?
A)0.11
B)0.33
C)3.0
D)9.0

Question

Quizplus · Accepted Answer

The exposure time is proportional to the square of the f-number. Tripling the f-number increases the exposure time by a factor of 3^2 = 9.

I Take Two Pictures of My Dog Kaycee