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post #10 of Old 06-24-2013 Thread Starter
hellosailor
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Re: Binocular Conundrum: Field of View?

Homer, the finger loop analogy falls short to me.

If the exit pupil size is supposed to correspond to the final size of the image on the retina, we have a fixed size image, let's say 5mm. That's at one end.

On the other end, we have a fixed life-size image. If we are viewing that image at "life" size, magnification 1, the FOV and the image on the retina are always the same, regardless of the finger loop blocking it. The finger loop effectively becomes the apparent exit pupil size, and a smaller FOV only happens with a smaller apparent exit pupil.

Since the eye relief and the distance from the retina to the exit pupil image are pretty much the same on all the binocs...I just don't buy the finger loop moving around as being analogous to what happens with binocs. Maybe I'm too dense to see it.

From what the binoc makers would have us see, everything behind the back lenses of the binocs is the same. Everything from the front lenses to the image is the same. And you're saying, if the only change is the length of the internal light path, that can account for a 50% change in the width of the FOV?

This must be why I wasn't a math major. Here, have another flagon of wine and try again. Please.
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