Increasing the diameter of a camera lens, while keeping its focal length unchanged, does more than just brighten the image on the film so that you can use a shorter exposure. It also
A) decreases the depth of focus so that objects at different distances will no longer all be in focus at once.
B) increases the size of the image on the film so that you get a close up.
C) decreases the size of the image on the film so that you get a wide angle view.
D) increases the depth of focus so that objects at different distances will all be in focus at once.

Question

Quizplus · Accepted Answer

Increasing the diameter of a camera lens (aperture) while keeping the focal length constant increases the amount of light entering the camera, which indeed brightens the image. However, a larger aperture also results in a shallower depth of field (not depth of focus, but the principle is similar), meaning that the range of distances within which objects appear sharp is reduced. This makes it harder to keep objects at different distances in focus simultaneously. Choices B and C are incorrect because changing the diameter of the lens does not directly affect the size of the image on the film; that is determined by the focal length and the distance to the subject. Choice D is the opposite of the correct effect.

Increasing the Diameter of a Camera Lens, While Keeping Its