Reward for lost Kraken!
Join Date: Apr 2006
Thanked 137 Times in 134 Posts
Rep Power: 11
Re: Binocular Conundrum: Field of View?
Not really groggy. I'm still stuck on the exit pupil being the same size, the eye relief being the same or very similar, and as a result the geometry, the size, of the image being put on the retina is going to be the same size.
If the "reality" is 100 feet wide, and the image on the retina is, let's say 10mm wide, then the apparent magnification is fixed and the only way to change the FOV is going to be by changing something, which will either result in a different magnification, or a reduction in the size of the image on the retina.
If all these binocs have the same "night factor", the same apparent size image as fixed by the exit pupil size, the iris, the retina, then they cannot have different FOVs. In order for the FOV to change, the magnification has to change (and they all say it doesn't) or the size of the image on the retina has to change. And they all say that's limited by the exit pupil size.
I'm no math ace, but either the binoc makers are tlaking in tongues, or there's something they just don't talk about which is in fact changing, along with the FOV. And for the FOV to change by 50%, the image on my retina has to become 50% larger as well, and that would mean some significant change in the back of the binocs. Exit pupil, eye relief, something has to show a similar huge change.
Or, they're all cooking the books with the numbers. You know, like "this boat sleeps eight!" Sure, as long as that's Snow White and her little friends, two to a berth. (G)