be easily calculated as the diameter of the objective lens divided by the magnification. The two formulas are of course equivalent and it is simply a matter of which information one starts with as to which formula to use. Photography The distance of the exit pupil from the sensor plane determines the range of angles of incidence that light will make with the sensor. Digital image sensors often have a limited range of angles over which they will efficiently accept light, especially those that use microlenses to increase their sensitivity. The closer the exit pupil to the focal plane, the higher the angles of incidence at the extreme edges of the field. This can lead to pixel vignetting. For this reason, many small digital cameras (such as those found in cell phones) are image-space telecentric. See also Transmittance Diaphragm (optics) Pupil magnification References External links A short definition of relative brightness Optics Science of photography nl:Intree- en uittreepupil