Here is a topic that I have not seen discussed since I have been on the forum. I wish I could take credit for thinking of it, but it was actually Mr. Alan Adler, who has authored many relevant binocular articles.
Anyone who has looked through a 3"-4" refractor at planetary magnifications will know that it sometimes takes a moment to "find" the exit pupil with your eye. The trick is usually to find the image from a distance and try keep your eye centered as you move to the eyepiece.
If this is a problem for one eye, Mr. Adler points out that it is hell to do simultaneously with both eyes. Not only that, but if only one eye is receiving light, the brain won't care because there is nothing to process on the blacked out side. So you might not even know that you were only using half of your binocular unless you closed one eye at a time to check.
For the vast majority of binoculars discussed on this forum, this is a non-issue because the exit pupils (Aperture divided by magnification) are typically several millimeters. But when you get into the interchangeable EP binos that I have been considering, I believe this could put an upper limit on usable magnification.
Just to talk numbers, my Canon 18x50's have a 2.8mm exit pupil and are NO problem. A Vixen 125mm zoom at 75x would drop to 1.7mm. Still easily usable? At one point Markus talked about taking Kowa Highlander's to 150x, which would drop the exit pupil to only 0.5mm! I suspect that this power on this bino would not be easily used, even if the collimation was perfect.
I would love to hear from anyone who owns, or has looked through binoculars with small exit pupils. Have you ever tried closing each eye in turn to see if the image disappears?
Still Thinking, Milt
Anyone who has looked through a 3"-4" refractor at planetary magnifications will know that it sometimes takes a moment to "find" the exit pupil with your eye. The trick is usually to find the image from a distance and try keep your eye centered as you move to the eyepiece.
If this is a problem for one eye, Mr. Adler points out that it is hell to do simultaneously with both eyes. Not only that, but if only one eye is receiving light, the brain won't care because there is nothing to process on the blacked out side. So you might not even know that you were only using half of your binocular unless you closed one eye at a time to check.
For the vast majority of binoculars discussed on this forum, this is a non-issue because the exit pupils (Aperture divided by magnification) are typically several millimeters. But when you get into the interchangeable EP binos that I have been considering, I believe this could put an upper limit on usable magnification.
Just to talk numbers, my Canon 18x50's have a 2.8mm exit pupil and are NO problem. A Vixen 125mm zoom at 75x would drop to 1.7mm. Still easily usable? At one point Markus talked about taking Kowa Highlander's to 150x, which would drop the exit pupil to only 0.5mm! I suspect that this power on this bino would not be easily used, even if the collimation was perfect.
I would love to hear from anyone who owns, or has looked through binoculars with small exit pupils. Have you ever tried closing each eye in turn to see if the image disappears?
Still Thinking, Milt
