Understanding Blackouts

[Marley]

All,

I have posted a few times in the past regarding different bins and blackout and I am now more confused than ever.

I think the problem may be with my definition of blackout so I though I would ask the BF experts.

I recently purchased a pair of 8x42 ELs (18mm ER) Ultravid 8x50s (18mm ER), 7x42s (17mm ER) and a pair of 7x42 FLs (16mm ER) and I experience some level of what I would call blackout on all three bins (I have returned the 8x50s already and both 7x42s will probably go back this week if I can't find a solution).

I have adjusted eye cups in and out on all four models and as I hold the bins up to my eyes, I still get glimpses of blackout around the edges if my hands or arms move slightly. If I concentrate, I can hold a steady picture, but typically any hand, arm or panning movement brings about intermittant slight blackouts.

I called Eagle Optics and they were at a loss to explain it. My question for the group is:

Am I expecting too much from my bins? Does everyone get brief blackouts when not holding steady or should I continue in my quest for a bin that I can look through that gives me error-free problems? I realize that the exit pupil has to be centered on my eye, but regardless of how I set up my bins, I seem to have this same problem, albeit different degress for each bin.

Thanks to anyone that can help.

Rgds,

Steffan

[Pileatus]

All,

I have posted a few times in the past regarding different bins and blackout and I am now more confused than ever.

I think the problem may be with my definition of blackout so I though I would ask the BF experts.

I recently purchased a pair of 8x42 ELs (18mm ER) Ultravid 8x50s (18mm ER), 7x42s (17mm ER) and a pair of 7x42 FLs (16mm ER) and I experience some level of what I would call blackout on all three bins (I have returned the 8x50s already and both 7x42s will probably go back this week if I can't find a solution).

I have adjusted eye cups in and out on all four models and as I hold the bins up to my eyes, I still get glimpses of blackout around the edges if my hands or arms move slightly. If I concentrate, I can hold a steady picture, but typically any hand, arm or panning movement brings about intermittant slight blackouts.

I called Eagle Optics and they were at a loss to explain it. My question for the group is:

Am I expecting too much from my bins? Does everyone get brief blackouts when not holding steady or should I continue in my quest for a bin that I can look through that gives me error-free problems? I realize that the exit pupil has to be centered on my eye, but regardless of how I set up my bins, I seem to have this same problem, albeit different degress for each bin.

Thanks to anyone that can help.

Rgds,

Steffan

Steffan,

The consistency of the problem leads me to believe you may be tilting the bin up or down slightly. If you are, this will surely develop the blackouts you describe.

Do you wear eyeglasses?

John

[Marley]

Hi John,

No eyeglasses here and I think that I am holding them properly. Interesting enough, when I ask my wife to have a look (no glasses either), she has the same problem.

Again, I can get the bins aligned to the point where I don't have a problem, but if I move at all, I get the intermittant problems.

Thanks for the help.

Steffan

[iporali]

No eyeglasses here and I think that I am holding them properly. Interesting enough, when I ask my wife to have a look (no glasses either), she has the same problem.
Steffan,

If you are easily disturbed by blackouts I think you just should keep the binos further away from the eyes - maybe even at the expense of field-of-view. The problem is also usually worst when the eye iris is very small (= in bright light), so if you would like to experiment with the blackouts, you could try to wear sunglasses when looking through the binoculars (to bring the binos farther and to dilate the iris). The other option to consider could be binoculars with less eye-relief. You are definitely entitled to feel comfortable with your binoculars.

Good luck, :t:

Ilkka

[Marley]

Thanks Ilkka,

I did try the sunglass experiment and indeed, the problem is associated with direct sunlight. Alas, I don't really want to wear sunglasses when using my bins.

I ordered a pair of 10x50 Ultravids (ER = 14.8 mm), as I am also interested in a pair of 10x bins and I want to further test the shorter ER theory. I will report back once I receive them.

I do have a question though. I am still interested in a pair of 7x42 bins, but all of the top contenders seem to have ER of 16 mm or higher, which seem to cause me problems.

Does optical physics disallow the use of shorter ER for the lower power bins or are manufacturers just focusing (no pun intended) on the eye glass wearers? If you know of any high quality 7x42 bins out there that have shorter ER, I would appreciate the information.

Thanks again for your advice. Your knowledge benefits us all! :clap:

Rgds,

Steffan

[Alastair Rae]

Perhaps I can punt a theory. Have you balanced the two barrels - adjusted the diopter on the one with the wheel? (Assuming it is the right one, close right eye, focus on middle distance object with left, close left, open right and adjust wheel until happy.)

I think if they're not adjusted and maybe a bit of self-correcting astigmatism could produce odd effects when the eyes try to follow something.

[iporali]

I do have a question though. I am still interested in a pair of 7x42 bins, but all of the top contenders seem to have ER of 16 mm or higher, which seem to cause me problems.

Does optical physics disallow the use of shorter ER for the lower power bins or are manufacturers just focusing (no pun intended) on the eye glass wearers? If you know of any high quality 7x42 bins out there that have shorter ER, I would appreciate the information.
Steffan,

Thanks for your kind words.
Sorry, but I am not aware of any modern full-size roof-binoculars with short eye-relief. However, if you don't mind older porro-design, there may still be Swarovski Habichts (8x30, 7x42 and 10x40) which are famous for their very sharp and "easy" view - and short eye-relief. I think Henry Link could make you a longer list of suggestions ;).

Good luck,

Ilkka

[Marley]

Hi Alastair,

I don't think the problem is one of diopter setting, as I still have very good eye sight and every time I try to adjust the diopter setting on any pair of bins, I end up at the 0 point.

I am learning, however, that extra-long ER does not come without a price. As others on BF have noted, extra-long ER can produce blackouts. I just wish that the suppliers understood this fact. They seem to be racing to produce products with longer and longer ER to accommodate those of us that wear glasses with no regard for those that don't. In my opinion, there ought to be a happy medium somewhere in there.

Thanks for the help.

Rgds,

Steffan

[kabsetz]

Steffan,

What happens if you twist out the eyecups of your 7x42 FL one click? They have three click-stops, and the first reduces the eye-relief from 16 to 12 millimeters (measured, not taken from specs). If you need something between the 16/12 mm settings, the cups will probably stay put where you twist them. If not, figure out the correct position, and glue yourself a pair of rubber O-rings of the right thickness to keep the eyecups from being pushed in all the way. With all due respect, with the nice selection of binoculars you have acquired, I'd be surprised if you cannot make one of them work for you.

Kimmo

[Infinity]

Hi Marley,

> I recently purchased a pair of 8x42 ELs (18mm ER) Ultravid 8x50s (18mm ER), 7x42s (17mm ER) and a pair of 7x42 FLs (16mm ER)

Lucky you! (OK, you've already returned some...)

> Does optical physics disallow the use of shorter ER for the lower power bins...

There is no lower limit for ER in optical physics. It entirely depends on the type of eyepiece (Kellner, Erfle, Nagler, ...). However, as you anticipated it, the manufacturers are focusing on eye glass wearers. They don't want them to be excluded from enjoying the whole field of view (and in turn to not buy the bin).

It should always be possible for a large ER to be compensated by a longer eye cup, but not vice versa (or your eye will stick to the eyepiece). You also have to take into account that the eye ball is turning around an axis which lies far behind the exit pupil position. So if you are turning your eyes without slightly re-centering the bin, chances are great that you lose some part of the field of view.

The correct setting of the interpupillary distance is of high importance for not having too much vignetting (blackouts) due to moving the bin. And remember, an 8.5x42 EL has a 4.9 mm exit pupil diameter, and your eyes may have 3 mm pupil diameter. Move only 1 mm sideways or tilt your eye a bit and you start losing field of view.

So, all in all, I think, nobody is free from sometimes having blackouts :-) , but there are centainly models where the effect is more visible than for others.

Greetings, Infinity from Germany

[Marley]

All,

Thank you for all of the help with these blackout issues. With all of your help and a bit of research on my own, I think I have my problem defined.

First of all, eye relief is a function of binocular design and it is not changed by eye cup setting. Eye relief is simply the distance between the ocular lens and the focal plane that will give the user a full field of view. Any closer or farther away from this focal plane and the user starts to lose FOV. It is up to the user to fill the ER with either eye cup, glasses or a combination of both.

In my experience, binocular designers are making bins with eye cups that range from all the way closed (flush with the binocular body) to extended to the ER limit. Unfortunately, they do not seem to extend much beyond that point.

I say this because I believe that this is the root of my problems. When I use a pair of bins, I like to place them against my eyes, and not hold them away from my face at all. I also seem to have eye sockets that are somewhat recessed, as the eye cups typically fit close to my eyes and don't allow much light in. With this being the case, when I extend the eye cups all the way out and place the bins to my eyes, I get intermittant blackout (I don't wear glasses). In my opinion, this is because my cornea is now in front of the optimum ER. Anyone that plays with the eye cups on a pair of bins and doesn't extend them far enough will find that they will get blackouts. With my cornea being too close to the ocular lens, I get the same effect.

Let me use an example to illustrate. If a pair of bins has an ER of 18mm, that is the distance that your cornea needs to be from the ocular to obtain full FOV. Typically, a non-glass wearer will have to extend the eye cups all the way to gain an cornea/ocular distance equal (or close to) the ER. Here's is the deal. If you are like me and the bin eye cups tend to set deeply into the eye socket (and I like it that way), you are effectively shortening the distance between cornea and ocular lens, the same way you would if you turned in the eye cups in one notch. To fix this problem, you would need eye cups that extend PAST the optimum ER to compensate for the eye socket depth. It has been my experience that manufacturers do not design eye cups to go much past the designed ER.

To make a long story short, this is why I cannot seem to get rid of the intermittant blackouts, regardless of brand, bin size or eye cup setting. My problem really is a function of today's eye cups not extending past the optimum ER combined with my relatively deep eye sockets.

What to do? I have an experiment in the works. Ilkka advised me to look for bins with a shorter ER. I believe that he is correct, but I went one step further. The current Leica Ultravid line uses the same eye cup design for the 7x42, 8x42, 10x42, 8x50, 10x50 and 12x50 bins. I have been looking at a pair of 10x50s and they have a 14.8mm ER. My theory is that the eye cup will extend out to ~18mm to accommodate the ER of other bins in the line and should provide me with ~3.2 mm of extension past the optimum ER, this allowing me to hold the bins close to my eyes and not get blackouts. I will let everyone know if my theory is correct next week when I receive the new Leicas!

Thanks again to all at BF for the help. This is truly a great forum! :bounce:

[henry link]

I have a couple of more suggestions. Some eyecups like the Swarovski EL/SLC can be screwed out a bit beyond the normal range of adjustment and still work. Just keep turning beyond the fully extended stop as if you were removing the eyecup. University Optics offer a range of add on rubber eye shields which have the effect of extending the length of the eyecup by about 3mm when in place. The 40mm-44mm size fits the Zeiss FL and the Swarovski EL, and probably many other binoculars. In Europe APM Telescopes sell what appear to be the same eye shields.

[Marley]

Hi Henry,

Thanks so much for the help.

I looked at the University Optics site and they seem to be largely a telescope store and their website does not have a parts catalog. Can you please pass on a bit more information regarding the eye shields so that I can call and order some? I just want to make sure I order the right parts.

Thanks again!

Rgds,

Steffan

[henry link]

Steffan,

The printed catalogue has the add on eye cups, but not the website. The ones I mentioned are eyecup type B, 40-44mm size, $7.95 ea. They have wing shaped side eye shields which can be folded down or completely cut off. One possible problem with them for some people will be insufficiant nose clearance, as they increase the diameter of the binocular eyecup as well as extending its length.

Henry

[kabsetz]

Steffan,

For some reason, when I wrote my response earlier I was picturing you wearing glasses. Now that I re-read the whole thread, I notice you don't, and that changes the picture.

I have the same problem as you with many binoculars (I also don't wear glasses), although not as severe. The Swarovski EL's, Leica Ultravid 8x32 and Nikon SE's, to name a few, have eyecups which do not extend far enough for me to prevent blackouts. The bit of information I'd like to offer here is that actually the eye-relief distance in all of the binoculars I have measured is longer than the eyecup extension, and the difference is not the same for different models. Further complicating the situation is the differing diameters and edge softness of different eyecup designs. Some sensible advice has been offered above, but the bottom line is that you really cannot trust written information and must try out yourself, as you are finding out the hard way.

Kimmo