Question

is the distance between the lens equal to the sum of focal lengths of the lens

Answer 1

Answer:

Explanation:

Not necessarily. For a simple lens, where the optical centre of the lens is on the lens, this is true; the distance between the lens and the film or sensor (in modern cameras) of a camera equal to its focal length, otherwise we are no "on focus" and we will not have a clear picture.

However in photography we have usually complex lenses. In complex lenses the optical center, most of the time is not inside the lens system (but always on the optical axis), i.e. the focal distance (the distance between the optical center and the focal point) is different from the distance between the lenses and the focal point. In this case, the distance between the lenses and the film of the camera is NOT equal to its focal length.