The constant is 53 because that’s what my calculated said
The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor.
Answer for the question is zero
9 points 9 points 9 points