BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="denco@comcast.n" data-source="post: 3623582" data-attributes="member: 25300">"The real contributing factor in image brightness is the size of the EXIT PUPIL and the spot presented to the receptors in the eye. "That is not exactly true. The size of the Exit Pupil is important but the brightness of that spot measured in Lux also makes a difference. That is why binoculars with equal size exit pupils but different transmissions will perform differently. The one that transmits at a higher efficiency will appear brighter because the light intensity of the exit pupil cone will be brighter and the eye will perceive it. Kind of like the difference between a floodlight and a spotlight. Both exit pupil size and transmission are important in a low light binocular.</blockquote>