1. The problem statement, all variables and given/known data Why is the depth of field greater, and the image sharper, when a camera lens is "stopped down" to a larger f-number? Ignore diffraction. 2. Relevant equations f-number=f/D where D is the diameter of the hole. 3. The attempt at a solution At a larger f-number, the diameter of the hole is smaller so there is less exposure, although I'm not sure what that has to do with the depth of field. Can someone help me?