What is relative brightness & exit pupil all about?
Relative Brightness and Exit Pupil are determined mathematically. The exit pupil of a binocular is the disc of light you see in the eyepiece when holding a binocular at arms length towards a bright light. To compute Exit Pupil: divide the diameter of the objective lens in millimeters by the power of the binocular. To compute Relative Brightness: square the Exit Pupil. Example 7×35, means the prism binocular described magnifies seven times and has an objective lens of 35 millimeters. Exit pupil equals 5 and 5 squared equals a relative brightness of 25.
