I have come to realize that regardless of other exceptional optical qualities, black-out issues can render a superb binocular either unuseable or relatively harder to use. For example many people find the wonderful Nikon SE series fantastic optically, but useless due to black-outs. From reading these threads I rarely find someone with a black-out problem on Leicas, yet I do have a problem with Leicas while the Nikon SE is the easiest view I have ever had. So I'd like to probe some causes and effects relating to black-outs with you optic experts.
1) Define "black-out". Let me try to describe the problem I have with my two Leicas. Both binoculars offer a large "picture window" view that more than fills my eye, to the point where I can hold the bin stationary and move my eyeball around inside the view to direct my attention to various points within. But when I do that, I get a slight greying, going to black if I go extreme left or right.
2) Obviously setting IPD is very important. That is pretty easy, just move it in or out for the best view.
3) What does eye relief have to do with it?
4) Glasses or no glasses, does that change anything?
5) Eye corrections within the diopter adjustment. I am a +1.25 in one eye and +1.75 in the other, easily within the diopter setting so I go without glasses. Are black out isues more or less a problem for far sighted (hyperopes?) or myopes, or does it matter?
6) What causes black-outs?
7) Other that trying the bin personally, is there a way to determine if you are going to have black out problems? For a lot of us, many bins that we are interested in are not available locally.
8) Is there any one person who doesn't have a black out problem regardless of bin? Is there a middle of the road, "standard" eye-face combination that works with everything?
It is very frustrating for me to have to consider selling my wonderful 8x32BN, solely for this slight issue when the bin is so perfect for me in every other area.
Thanks for your help.
John
I think I pretty much answer these ER questions on this thread
http://www.birdforum.net/showthread.php?t=125903
I think glasses do change it. In this thread starting near post #19 and #21
http://www.birdforum.net/showpost.p...04&postcount=19
http://www.birdforum.net/showpost.p...07&postcount=21
the whole thread is here for context
http://www.birdforum.net/showthread.php?t=129030
Wearing eyeglasses changes the apparent distance from ocular lens to entrance pupil of the eye. You can see this if you pay attention to how th e person looks: if the eye looks magnified the person has positive eyeglass lens and is a hyperope.
I speculate that corrected myopes have a better time than corrected hyperopes with short ER bins if they're correcting their vision (i.e. if they're wearing glasses) because the diverging lens expands the light cone moving the exit pupil further back than it would be giving myopes a "better chance" of getting the bins exit pupil and their eye's entrance pupil in the same place.
But corrected myopes will have a worse time with long ER bins suffering from more blackouts. And this does seem to match me a myope with close fitting glasses doesn't work well with bins assumed to be made for normal fitting eyeglasses especially in my more myopic eye (I come with the test case built in!). And in fact if I add some extra eyecup on my Yosemite the problem goes away (continuously adjustable eyecups are the best solution with added O rings the next best choice ... rubber eyecups suck, of course).
But if you don't wear eyeglasses with bins you don't see a difference in ER (there's nothing there to change it).
That should go some way to answering your questions. Anything missing?
They are annoying when they are there, yes. I hold the binoculars such that they rest on the top below my eye brow. So they are not as close to the eye as they could be. That may work for some facial types, not all.
Models with many click stops on the eye cups may be helpful.
Good luck. Try different models in person. Borrow some.