Questions about Black-outs... (1 Viewer)

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.php?p=1352504&postcount=19
http://www.birdforum.net/showpost.php?p=1352607&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.

Kevin Purcell said:

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.

Click to expand...

Conversely corrected hyperopes should be able to deal better with excessive ER.

Which is what you are and what you have.

My hypothesis says if you put your positive eyeglasses on and reset the eyecups for eyeglass use (all the way in or thereabouts) then you should have fewer ER blackout problems.

This rather depends on the manufacturer guessing correctly what vertex distance your eyeglasses actually have. If they get that wrong you may still have blackout problems (or you may be too far back though I doubt that with the measured ER for the SE).

Worth a try ...

You make an interesting but perhaps not infallible test case.

Kevin Purcell said:

Conversely corrected hyperopes should be able to deal better with excessive ER.

Which is what you are and what you have.

My hypothesis says if you put your positive eyeglasses on and reset the eyecups for eyeglass use (all the way in or thereabouts) then you should have fewer ER blackout problems.

This rather depends on the manufacturer guessing correctly what vertex distance your eyeglasses actually have. If they get that wrong you may still have blackout problems (or you may be too far back though I doubt that with the measured ER for the SE).

Worth a try ...

You make an interesting but perhaps not infallible test case.

Click to expand...

Well that was an easy and worthwhile test, here's what I discovered:

1) It actually worked, I tried two pair of glasses, my custom made prescription glasses which are rather compact, and an off the shelf +1.50 reading glass, sort of horn rimmed style. With the eye cups all the way in I was able to see with out blackouts, though I don't like adding the questionable glass (plastic) of my everyday abused glasses to the equation.

2) Looking through the glasses pretty much forced me to concentrate my view on the center of the image, which may have eliminated the blackouts that predominantly happen when I move my eyeballl around the rather expansive view of the Trinovids.

3) That made me wonder what my BNs would be like if I used them without glasses and tried to limit that panning within the image, but instead move the bins with my head. I tried that, voilla! No blackouts.

4) Then I tried the SEs again and noticed that for some reason, (smaller FOV?), I hadn't been and wasn't near as tempted to move my eye around inside the view. When I forced myself to try that, instant, dramatic black-outs.

So my conclusion is that it isn't a vice of the binocular to offer such a wide, big picture view, it's an asset that has some limitations. Also it may not be fair to conclude that an 8x32BN is not great because it is slightly inferior to the wonderful 8x32SE. The SE has pretty big shoes to fill considering its size.

Thanks for the suggestion. I'm also going to try them with my contacts correcting my vision and the eye cups all the way out.

John

Sounds like you still need a bit more distance from the eye to the oculars lens of the bin.

Sticking with glasses and adjusting them so the vertex distance is larger (i.e. the eyeglass lens is further away from your eyes).

I'm considering getting a new pair of birding glasses that sit further away as I'm finding my close glasses give me too many "almost blackout" situations with modern long ER bins.