perterra
Well-known member
Most of the time with less than 15 mm I wont even bother picking them up, because most times they are nearly useless. Even 15 is suspect, 17 or 18 is usually my starting point.
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Why exactly do most binoculars feel like "tunnel vision", but some don't? (1 Viewer)
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Most of the time with less than 15 mm I wont even bother picking them up, because most times they are nearly useless. Even 15 is suspect, 17 or 18 is usually my starting point.
A2GG
Beth
Yes, centering or lining up my eyes to the image/EP is annoying
with small EP. A larger EP is not fussy and just easy. When I need
to get the bin up to my eyes quick it helps a lot more to have larger
EP. Lee said I could get used to a 4mm EP and find that
perfect spot to place the oculars on the glasses, but I tried and simply
don't have the patience and/or skill to get it right. I've learned to
enjoy the 8x42 format now.
Regarding ER, I've always read that eyeglass wearers should go
for 16mm minimum.
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This is one area where composite barrels could help a lot.
Thinner, lighter barrels would allow more length and more aperture,
so the eye relief and the exit pupil would both increase.
It wouldn't be cheap, making ployimid/kevlar cloth barrels
and fitting in molded parts after, but what's a premium brand for?
Already, Zeiss has some ingenius tricks to make the phase path longer,
although that adds a big dose of glass.
Thinner, lighter barrels would allow more length and more aperture,
so the eye relief and the exit pupil would both increase.
It wouldn't be cheap, making ployimid/kevlar cloth barrels
and fitting in molded parts after, but what's a premium brand for?
Already, Zeiss has some ingenius tricks to make the phase path longer,
although that adds a big dose of glass.
elkcub
Silicon Valley, California
Bearclaw,
Actually, tunnel vision results from restricting the eye's field of view, or the area of retinal stimulation. Such restriction always occurs with binoculars because the apparent FOV (AFOV) is always less than what the natural eye can see. (The AFOV physically corresponds to the retinal area that is stimulated by the binocular's image.) You are quite correct, however, that the AFOV can be further limited if the exit pupil of the instrument is prevented from reaching the eye's pupil because of eyeglass standoff. If you examine it carefully, the "reduced image" you mentioned has a much smaller field. So, eye relief is definitely a critical design factor.
Not all eyeglasses are the same, however, and I don't just mean how much physical standoff they require. I mean the corrective lens prescription makes a non-trivial difference (a topic that, strangely enough, not even Brother Brock has picked up on).
Eyeglass prescriptions optically alter the eye's effective pupil diameter and importantly the entry pupil location of the eye by as much as 3-4mm. A nearsighted person with -3 correction, for this reason, will often find 15mm eye relief satisfactory, whereas a farsighted person with +3 correction (like me) isn't generally happy with less than 18mm. The near sighed person will also be able to get the instrument to focus closer, while experiencing a smaller image and wider apparent field. Brightness doesn't change, by the way, because the increase in pupil diameter is offset by the increase in AFOV, so that the light per unit area on the retina remains unchanged.
Sorry if this sounds argumentative, but not even eyeglass manufacturers like Zeiss mention it.
Ed
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A2GG
Beth
Very interesting and useful info...thanks for explaining that.
brocknroller
porromaniac
"Brother Brock" is too busy writing about the Marcellus and Utica shale plays so he can have tomorrow off to celebrate the 75th anniversary of Gone with the Wind by seeing the movie on the BIG screen for the first time to research eyeglasses! That's why we rely on you for the 411 on visual science. But when you don't chime in, I give it a shot.
I'm far sighted and do require extra ER even with bins that have good fitting eyecups that fit inside my deep eye orbits. I've argued this point before and some BF expert said that being farsighted didn't make any difference.
Your explanation explains how eyeglasses change entrance pupil position and needed ER, but not how presbyopia affects ER w/out the use of eyeglasses.
When I was younger, I was nearsighted and I got by with less ER (as long as the eyecups weren't so wide as to hit the bridge of my nose or not fit into my eye orbits), but now with presbyopia, even w/out glasses, I need to back off from the eyecups of some bins to avoid blackouts whereas other users can sink their eyes into the eyecups of those same bins without experiencing blackouts.
"Doctor, my eyes, tell me what is wrong, was I unwise to keep them open for so long?"
Friar Brock (recent promotion)
mooreorless
Well-known member
Hi Ed,
I am Myopia[nearsighted] in my left eye -2.0 diopters and ok except for presbyopia in my right eye[62 yrs.]. I will have to check out some of this.
I am kind of confused by Brock saying that his eyes changed from near sighted to far sighted or is that age related presbyopia and is that what he is saying? So Brock now you can see far away w/o glasses? My presbyopia is moving further out.
bearclawthedonut
Well-known member
elkclub:
Nonsense! Of course when you look through a pipe - you have a restricted FOV. Just like when you look through any optical device - you have a restricted FOV. However, if you place your eye beyond the focal point/plane, then you see less of the image (loosing a portion of the image perimeter) and/plus/in addition - the image appears to be further away. Optically, less of the image is presented to your eye - due to eye placement. This is "tunnel vision". If you poke a stick into your eye you might restrict your FOV - but it will not be "tunnel vision". If you close your eyes, it will surely restrict your FOV - but it will not be "tunnel vision".
Satisfactory eye relief for eyeglass wearers mainly depends on the distance that feels comfortable for you between your eyes and the lens of your eyeglasses PLUS the thickness of your eyeglasses. I am nearsighted (that means I have trouble reading highway signs) with my old glass lenses I required 17 to 18 mm of eye relief for comfort. With my new smaller polycarbonate lenses, I only require 16 mm of eye relief.
But the amount of eye relief that I require is of secondary importance. The most important factor is how the various binocular manufacturers measure eye relief. For example, I find that 16 mm as measured by Zeiss is far more generous then 18 mm as measured by Burris. I find Zeiss to be understating, Nikon and Vortex to be accurate and Burris, Leupold and Swaro to be overstating.
Finally, I see no mystery in regard to partial or full "blackouts". If the binoculars are NOT defective, then all "blackouts" are caused by improper eye placement. Both eyes need to be placed at the exit pupils with both ocular lenses being the same distance from each eye. The closer both eyes are to the center of the exit pupils then the better and more stable the view will be. Additionally, there will be greater comfort in viewing. This is not a secret.
bearclawthedonut
Nonsense! Of course when you look through a pipe - you have a restricted FOV. Just like when you look through any optical device - you have a restricted FOV. However, if you place your eye beyond the focal point/plane, then you see less of the image (loosing a portion of the image perimeter) and/plus/in addition - the image appears to be further away. Optically, less of the image is presented to your eye - due to eye placement. This is "tunnel vision". If you poke a stick into your eye you might restrict your FOV - but it will not be "tunnel vision". If you close your eyes, it will surely restrict your FOV - but it will not be "tunnel vision".
Satisfactory eye relief for eyeglass wearers mainly depends on the distance that feels comfortable for you between your eyes and the lens of your eyeglasses PLUS the thickness of your eyeglasses. I am nearsighted (that means I have trouble reading highway signs) with my old glass lenses I required 17 to 18 mm of eye relief for comfort. With my new smaller polycarbonate lenses, I only require 16 mm of eye relief.
But the amount of eye relief that I require is of secondary importance. The most important factor is how the various binocular manufacturers measure eye relief. For example, I find that 16 mm as measured by Zeiss is far more generous then 18 mm as measured by Burris. I find Zeiss to be understating, Nikon and Vortex to be accurate and Burris, Leupold and Swaro to be overstating.
Finally, I see no mystery in regard to partial or full "blackouts". If the binoculars are NOT defective, then all "blackouts" are caused by improper eye placement. Both eyes need to be placed at the exit pupils with both ocular lenses being the same distance from each eye. The closer both eyes are to the center of the exit pupils then the better and more stable the view will be. Additionally, there will be greater comfort in viewing. This is not a secret.
bearclawthedonut
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brocknroller
porromaniac
Yes, I used to need glass to see far away (nearsighted), but upon each visit to the optometrist, my eyes became better and better until about 10 years ago I found I no longer needed glasses to see far away so I stopped using them. This happened to my cousin, but he thinks it was due to him using the Bates Method.
Not long after my prescription started changing, I started needing reading glasses to see close up. I wrote a humorous story about this, titled "How I Became a Presbyopian Despite My Religious Objections."
My prescription wasn't exactly the same for both eyes but not a 2 diopter differences like yours. If both your eyes were farsighted, you wouldn't need glasses for myopia.
Do you have prescription reading glasses? With that much difference between your eyes, an off-the-shelf pair would be difficult to use. You'd have to keep your computer screen or newspaper just at the right distance where the right and left eyes overlapped at close focus.
Back to shale leasing trends....
Brock
elkcub
Silicon Valley, California
I get why you think my posts are "nonsense" ... but I'll live with it.
Thanks,
Ed
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elkcub
Silicon Valley, California
All,
What I summarized in the last paragraph of post #24 comes from Smith and Atchison's book: The Eye and Visual Optical Instruments, (1997). I've presented this before on BF, so anyone interested can review the development and do the exercises to their own satisfaction. Of course, the reference has nothing to do with individual pathological conditions. Fortunately, my own eyes are ho-hum in the scheme of things.
Brother Brock, I'm starting to experience your sense of mission, so I'm gonna take a nap until it dissipates.
Ed :gn:
PS. Some sections of the book can be read on Amazon, but unfortunately not the section on eye relief calculation.
What I summarized in the last paragraph of post #24 comes from Smith and Atchison's book: The Eye and Visual Optical Instruments, (1997). I've presented this before on BF, so anyone interested can review the development and do the exercises to their own satisfaction. Of course, the reference has nothing to do with individual pathological conditions. Fortunately, my own eyes are ho-hum in the scheme of things.
Brother Brock, I'm starting to experience your sense of mission, so I'm gonna take a nap until it dissipates.
Ed :gn:
PS. Some sections of the book can be read on Amazon, but unfortunately not the section on eye relief calculation.
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mooreorless
Well-known member
Hi Ed,
Thanks for the link and "all" your posts!!:t:
Thanks for the link and "all" your posts!!:t:
brocknroller
porromaniac
My mission, should I decide to accept, is to get these two &$#&! articles done before Gone with the Wind tomorrow, no more, no less.
Brock
brocknroller
porromaniac
Why can’t manufacturers agree on a standard for ER?
I found this review of the 10x42 SV EL, which I think might be of interest to the discussion of ER, how various companies measure it, and how accurate those measurements are. Of particular interest is the question he asks as the end of his comments, which begs a further question, if there is an ISO standard measurement for AFOV, why not for ER?
There's also a link to his "Open Letter to Alpha Bino Makers" higher up on the page that could be a topic for its own thread.
Here's what he said about the ER on the 10x42 SV EL:
Swarovski has made much of the very long eye relief in the new ELs, claimed at 20mm. I have long been moaning about eye relief, because you need plenty of it to make binos comfortable to use with glasses. Nikon has always been a favourite manufacturer because they realised the need for good ER long ago, whilst the “Alpha makers” were (and are) still routinely offering too little (13mm, when 16mm is really the minimum in my opinion).
However, Swarovski have clearly introduced another innovation with the ELs, though: the short millimetre, because mine measure at about 15mm, noticeably less than the 10x42 Nikon SEs and less than the Zeiss 7x42 that claim 16mm, but are actually a bit more.
I’m guessing that Swarovski measure the ER from the surface of the deeply concave eye lens, but even so the figure they give is a bit disingenuous. This situation is particularly annoying for customers, because Swarovski aren’t even consistent: the SLC 15x56s have exactly the claimed 13mm. This situation is by no means unique to Swarovski: I have seen similar discrepancies from all the major makers. Why can’t manufacturers agree on a standard for ER?
Webpage:
http://scopeviews.co.uk/SwaroEL.htm
Brock
I found this review of the 10x42 SV EL, which I think might be of interest to the discussion of ER, how various companies measure it, and how accurate those measurements are. Of particular interest is the question he asks as the end of his comments, which begs a further question, if there is an ISO standard measurement for AFOV, why not for ER?
There's also a link to his "Open Letter to Alpha Bino Makers" higher up on the page that could be a topic for its own thread.
Here's what he said about the ER on the 10x42 SV EL:
Swarovski has made much of the very long eye relief in the new ELs, claimed at 20mm. I have long been moaning about eye relief, because you need plenty of it to make binos comfortable to use with glasses. Nikon has always been a favourite manufacturer because they realised the need for good ER long ago, whilst the “Alpha makers” were (and are) still routinely offering too little (13mm, when 16mm is really the minimum in my opinion).
However, Swarovski have clearly introduced another innovation with the ELs, though: the short millimetre, because mine measure at about 15mm, noticeably less than the 10x42 Nikon SEs and less than the Zeiss 7x42 that claim 16mm, but are actually a bit more.
I’m guessing that Swarovski measure the ER from the surface of the deeply concave eye lens, but even so the figure they give is a bit disingenuous. This situation is particularly annoying for customers, because Swarovski aren’t even consistent: the SLC 15x56s have exactly the claimed 13mm. This situation is by no means unique to Swarovski: I have seen similar discrepancies from all the major makers. Why can’t manufacturers agree on a standard for ER?
Webpage:
http://scopeviews.co.uk/SwaroEL.htm
Brock
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Kammerdiner
Well-known member
Interesting review. Thanks for pointing it out. Here's a link:
http://scopeviews.co.uk/SwaroEL.htm
From what I can tell, manufacturers have steadily improved the eye relief numbers over the years. Those with glasses have a pretty easy time of it these days.
I've not used the 10x42 SV, but the 8.5x42 and 8x32 both have what I'd call an honest 20mm eye relief. The SV eyepiece is recessed a bit more than, say, a Zeiss FL, but with my current glasses, the 16mm FL is right on the edge of comfortable. I have to push against the glasses just a bit. Both Swaros have notably more eye relief than that. Clear field stop, no pushing.
I like to see 17-20mm, but I can generally live with 15mm. Below that is automatically disqualified for me.
As an aside, I tried polycarbonate lenses once. Once! How people live with the CA of those things is just beyond me. I lasted two weeks, but had to go back to plastic. Has anything changed on that front?
Mark
http://scopeviews.co.uk/SwaroEL.htm
From what I can tell, manufacturers have steadily improved the eye relief numbers over the years. Those with glasses have a pretty easy time of it these days.
I've not used the 10x42 SV, but the 8.5x42 and 8x32 both have what I'd call an honest 20mm eye relief. The SV eyepiece is recessed a bit more than, say, a Zeiss FL, but with my current glasses, the 16mm FL is right on the edge of comfortable. I have to push against the glasses just a bit. Both Swaros have notably more eye relief than that. Clear field stop, no pushing.
I like to see 17-20mm, but I can generally live with 15mm. Below that is automatically disqualified for me.
As an aside, I tried polycarbonate lenses once. Once! How people live with the CA of those things is just beyond me. I lasted two weeks, but had to go back to plastic. Has anything changed on that front?
Mark
bearclawthedonut
Well-known member
Brock:
I strongly agree. I do not understand why a millimeter can not remain a millimeter? Why it should suddenly become 0.9 mm or 1.1 mm? There needs to be common agreement on the starting and ending points; thus defining eye relief.
bearclawthedonut
I strongly agree. I do not understand why a millimeter can not remain a millimeter? Why it should suddenly become 0.9 mm or 1.1 mm? There needs to be common agreement on the starting and ending points; thus defining eye relief.
bearclawthedonut
A2GG
Beth
My lenses are polycarbonate and I've had them for several months now.
I'm not sure if the new ones are better or not, but I may have noticed
CA only once when I first started wearing the glasses. If it's there I don't
notice it now. However, sometimes I feel things don't look quite as vivid or sharp as they should compared to glass or plastic lenses. I've gotten used to my glasses and the type of view they provide.
So Mark,
Who wrote that encomium to the Swarovski EL in the "Scopeviews" link above?
Bob
Kammerdiner
Well-known member
A guy named Roger Vine. Here's his homepage:
http://scopeviews.co.uk/
He's reviewed quite a few binoculars, yet I don't think his name has ever come up on Birdforum.
Mark
