01-29-2015, 07:16 PM
Of course the focal length is independent to the sensor behind it. But also realize that you can make a 100 degree field of view 50mm lens and you can also make a 1 degee field of view 50mm lens.
Total luminance flux (aka the etendue of the system) is not the same as the energy density of the system which is described by the f number.
Total luminance flux (aka the etendue of the system) is not the same as the energy density of the system which is described by the f number.