The use of aspherical lenses leads to a reduction in the overall length of the binoculars and in some cases to a significant reduction in weight.
The interpupillary distance is the optimum distance between the eyepiece lens and the pupil of the eye.
In addition to the twilight number, the binocular exit pupil at the eyepiece of the binoculars is also very important for seeing in twilight (twilight vision).
