Ans:The exit pupil is the breadth of the stream of light leaving the eyepiece of the binoculars. It is a virtual aperture in an optical gadget and a small bright circle that can be seen in the eyepiece’s middle.
The higher the exit pupil number is, the brighter the image will be. So the best low light binoculars are the ones offering an exit pupil of 5 mm or higher.