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Eye relief?

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Old Tuesday 1st May 2018, 23:16   #26
Kevin Conville
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That's very fortunate. A lot must depend on anatomy, depth of eye socket and hence distance from eye to eyeglass lens. I couldn't use my 10x32 Leica with any glasses; I'd see maybe half the field. Fortunately I don't have to.
I have wire framed glasses with relatively small eye size of 55mm wide x 29mm high, and high index glass. I have to snug them close to my face but it's doable.

I also almost never do it as I wear contacts nearly all the time. It greatly simplifies seeing generally, and binocular use is much improved. I can also use over the counter Maui Jims instead of prescription sunglasses.
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Old Wednesday 2nd May 2018, 08:16   #27
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Maui Jims
These sound like exotic underwear............

Lee
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Old Wednesday 2nd May 2018, 09:50   #28
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These sound like exotic underwear............
That you wear on your face!

I don't expect you to know what these are, Lee. You see, I live in a place where people actually need sunglasses.
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Old Wednesday 2nd May 2018, 10:21   #29
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That you wear on your face!

I don't expect you to know what these are, Lee. You see, I live in a place where people actually need sunglasses.

If Maui Jim also sells waterproofs and rubber boots he could do well over here.
Lee

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Old Wednesday 2nd May 2018, 17:44   #30
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Alexis,
Does the U.S.A. thickness requirement for lenses apply only to glass or also to plastic lenses?

Can plastic lenses shatter and cause eye injury?...
I don't know. Will ask my eye doc next time I get a chance. Maybe someone else knows.

--AP
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Old Wednesday 2nd May 2018, 18:35   #31
Kevin Conville
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Binastro, Alex-

I googled and found this:

"Actually, this issue is fairly complicated, and even confuses many people
in the ophthalmic industry. First of all, the only lenses which have to
meet a specified minimum thickness are lenses which are sold as "safety
glasses". These must be no less than 3.0mm at the thinnest point on the
lens.

Although regular eyeglass lenses do not have a specified minimum
thickness, they nonetheless have to meet the FDA requirements for "impact
resistance." For glass lenses, this means that the lenses must undergo
heat or chemical tempering, then subjected to a "drop-ball" test (a 5/8"
steel ball dropped from 50 inches.)

Plastic lenses do not require special treatment or testing. They do,
however, require that lens manufacturers state under what conditions their
lenses will meet the FDA impact requirements. For each specific lens
material, lens manufacturers do this by "certifying" their lenses will
meet these requirements when processed to a certain minimum thickness and
processing standard. These recommendations are based on exhaustive and
continuous "batch" testing done as part of the manufacturing process. Any
lenses ground thinner than the manufacturers' recommendation will not be
in compliance with FDA impact requirements, unless the grinding laboratory
is willng to conduct their own tests. Since the drop-ball test oftens
mars the surface of plastic lenses, this is not a practical option for
most laboratories.

The upshot of all this is that a "standard of care" has developed
concering minimum thickness for various lens materials. For CR-39 lenses
(the lens material in about 70% of all eyeglasses in the U.S.), all
manufacturers that I'm aware specifiy a minimum center thickness of 2.0mm.
Minimum edge thicknesses depend on overall lens power. Some "high index"
and polycarbonate lenses are certified to meet impact requirements at
1.5mm centers, and, in some cases (very high minus powers), even as low as
1.0mm thickness.

I hope this helps clarify rather than confuse the issue. :->

Regards,

Steve
Sola Optical, USA"
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Old Wednesday 2nd May 2018, 20:22   #32
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Thanks Kevin, that's interesting stuff. I can't find the equivalent info for the EU but I'm sure something similar exists.

My lenses are 1.6 index so probably Mitsui Chemicals MR-8 which is rated very good for impact resistance. That compares to polycarbonate excellent and CR-39 good. In their illustrative examples, which appear geared for the US market, the minimum edge thickness is 1.5mm and centre thickness 1.4mm. For CR-39 is is 2mm for both. In practice that's prescription and frame dependant of course.

David
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Old Saturday 5th May 2018, 23:13   #33
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@ Bill / Chuck: Thanks for your advice!

I've checked out a 8x42 Noctivid at our local Leica Store today. Eye relief / ease of view is just perfect for me and my spectacles (eye cups fully retracted). Let's see to where this positive experience will lead me...

Tom
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Old Sunday 6th May 2018, 01:35   #34
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@ Bill / Chuck: Thanks for your advice!

I've checked out a 8x42 Noctivid at our local Leica Store today. Eye relief / ease of view is just perfect for me and my spectacles (eye cups fully retracted). Let's see to where this positive experience will lead me...

Tom
Tom, That's great news that you found a binocular that gives you the whole field.
In addition, it has excellent optics, so its a win-win, except for your pocket book...

If you want to shop for less pricey alternatives, you might check out the Zeiss Conquest 8x42 HD, and also the Vanguard Endeavor edII 8x42. Make sure your IPD works for them as well. Unless, of course, you've already tried these.

-Bill
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Old Sunday 6th May 2018, 02:18   #35
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Eye relief is a tricky thing for me. I can look through Nikon EII or Swift Audubon with short eye relief and no blackouts. I recently had to send back a pair of Leica Noctivid 8x42 because even at 18mm ER I was getting blackouts in certain portions. Yet my Leica Trinovid 8x32 BN with shorter eye relief is no problem. I use binoculars without eyeglasses.
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Old Sunday 6th May 2018, 02:56   #36
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Coolhand,

Interesting for someone to have blackouts not wearing glasses with 18mm eye relief. Is it possible that it was a flawed sample? I think you have experience with the EDG, how were they regarding eye relief.

Andy W.
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Old Sunday 6th May 2018, 03:38   #37
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Coolhand,

Interesting for someone to have blackouts not wearing glasses with 18mm eye relief. Is it possible that it was a flawed sample? I think you have experience with the EDG, how were they regarding eye relief.

Andy W.
Sounds like too much eye relief rather than not enough. Some people have similar issues with the Zeiss Conquest HD.

What is important is that the required eye relief of the individual (whether wearing glasses or not) matches the eye relief offered by the binocular (either through sufficient eye relief in the first place and/or being able to precisely adjust the eye cups to suit - this means they need sufficient range to accommodate that).



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Old Sunday 6th May 2018, 03:53   #38
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Thanks Chosen, perhaps the same plight has happened to Kingfisher regarding the Noctivid, is that why longer/different eye-cups were provided for the Conquest.

Andy W,
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Old Sunday 6th May 2018, 04:35   #39
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Thanks Chosen, perhaps the same plight has happened to Kingfisher regarding the Noctivid, is that why longer/different eye-cups were provided for the Conquest.

Andy W,
Chosen and Andy, I think you are right. I am thankful that there are a few binoculars that actually fit me really well WITH my glasses on. But its clear that when they accommodate me, others that don't need glasses may have a problem with the same binocular. But then, maybe 95% or more of all binoculars made fit the folks that don't need glasses.

-Bill
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Old Sunday 6th May 2018, 05:12   #40
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Bill,

Lack of adequate eye relief seems to be the more common issue with not being able to see the entire FOV, but aside from facial features and getting a glass to fit the bridge with sufficient IPD (we have all had one glass that just did not fit), the subject of too much eye relief perhaps needs to be discussed more often.

Andy W.
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Old Monday 7th May 2018, 07:58   #41
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Thanks everyone.

Lots of good questions to ponder the next time I change eyeglass frames and lenses.

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