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Message: <blockquote data-quote="elkcub" data-source="post: 3624258" data-attributes="member: 14473">Hi Gijs,I can't help but think that this post was partly responding to my post 43, because it specifically addresses the field-of-view (FOV) issue.  I've also studied the topic for quite a few years, and after retiring from NASA as a senior research psychologist in 2005 started on the development of an Excel model called "Elkcub's Binocular Brightness Stimulation" (EBBS).  I abandoned the effort under the weight of criticism that my limited optical background could not defend against at the time.  The key idea behind the model, that no one else was willing to accept, was that "perceptual" brightness, should be a function of the total mount of retinal stimulation; and that, in part, would necessarily involve the retinal projection area of the binoculars, otherwise known as the AFOV.  That notion was shot down by superior knowledge of the same kind of 'leading optical scientists' you now mention, and sadly I buckled under.   But it didn't sit well ('caus altho I may not be right, I'm never wrong!).  :king:We differ on only one point.  So let me ask this question.  When you say brightness is determined  by: "... the exit pupil and the amount of light entering the eye because of the light transmitted by the binocular...," would you not also agree that a binocular with a larger field of view must pass more photons through the exit pupil in order to cover its larger projection area on the retina, i.e., the AFOV?  The wider the field stop the more light enters the eye to accomplish this, although the size of the exit pupil remains unchanged.  The question then switches to: what evidence exists that the size of the retinal stimulation area is positively related to brightness?  Back in 2005 I struggled with that question, partly because my texts were dated and also because Google Scholar hadn't been invented.  By 2012, however, Watson and Yellott published "A unified formula for light-adapted pupil size," which basically answered the question in a curious way.  The eye's pupil size can be regarded as a measurable surrogate for brightness, in that it constricts as brightness increases.  Accordingly, the factors influencing pupil constriction also tell us indirectly what effects perceived brightness.  The factor of interest here is the "adapting field area," which corresponds to the binocular's AFOV.  You probably have the article, but I've attached it anyway.  We can discuss further.  Regards,Ed</blockquote>

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