Camera setting that adjusts the size of the aperture

FSTOP

Think of the term photographers use to describe how much light enters the lens—it’s often written with a slash, like "f/2.8," and controls depth of field.

This clue refers to a photography term where "F-stop" controls how wide the camera's aperture opens, directly affecting exposure and depth of field. The answer is shortened to "FSTOP" to fit crossword style, dropping the hyphen for brevity. It’s a straightforward definition with no wordplay—just a common technical term photographers use to adjust light intake.