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="elkcub" data-source="post: 3332515" data-attributes="member: 14473">Tobias,I have a few comments about the brightness assessment procedure.  According to your web article (below), pictures were taken of white light reflecting from a wall ~15" behind the ocular's eye lens and emerging through the objectives.  Assuming the light sources and camera settings were all done accurately, and so forth, I don't see how you could expect any other result than that the larger aperture instruments would produce brighter camera images.  Also, these brighter images do not necessarily suggest an increased brightness perception for someone using the binoculars, except under dark conditions when his/her eye pupils equal or exceed the largest exit pupil size.  They will not necessarily appear brighter under daylight conditions when the eye's pupils are equal to or less than the smallest instrument exit pupil.A way to control for this experimentally might be to mask the binocular objectives so as to produce a standard exit pupil size, e.g., 2.5 mm.  Under these conditions, the camera images would allow quasi-valid brightness comparisons; quasi-valid because the eye-brain system has it's own photopic sensitivity function that weights the light spectrum to produce brightness percepts.  Ed</blockquote>