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Is All ED Glass the Same?

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Old Thursday 6th December 2018, 03:27   #1
MUHerd
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Is All ED Glass the Same?

Hey all,

Something I have been curious about since I started reading up on Bino specs is the subject of ED Glass.

Now I don't know all the specs, coatings and technical jargon associated with this glass, but I would still like to know more about it. I know that all of the "Alpha Binos" list in their specs as having ED Glass. What I'd like to know is whether all of these ED Glass lenses and prisms are created equal. Is the ED Glass in the ZEISS binos the same as the ED glass in a set of Swaro's or Tract Binos or the many others that are said to have ED Glass in them?

I'd love to be able to look thru a set that has the best ED glass and compare them to my Pentax DCF HRII 10x42. I'm pretty sure I have never had the pleasure to use a set of binos with ED glass in them. I know I'd sure like to try a set and just see how they maintain their lofty platforms that they have attained.

Can anyone explain this to me and hopefully helping me to understand why these binos are so expensive and what goes into making a set of these ED Glass Binos.

Help me "see" what is present in these binos that enthusiasts are willing to shell out a lot of money to get the very best money can buy.

In NO WAY am I slamming these sets of ALPHA binos or complaining on their prices. The best comes with a price tag. I'm happy that there are people that have attained a level of success and love their hobby to such an extent that they will buy the best gear that they can possibly get.

Please explain ED glass from these various companies please.

Have a good week.
MUHerd
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Old Thursday 6th December 2018, 03:38   #2
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If my memory is correct, there have been a number of discussions on this forum about this very subject. I'm not going to try to find them because it might possibly ruin the good week you wished me.

Bob
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Old Thursday 6th December 2018, 05:15   #3
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Hi MUHerd,

As ceasar has observed, glass is often a topic here on BF and as you yourself have noted, ED is an unhelpful label, like 'all natural' on hot dogs, it leaves one none the wiser. One needs a glass supplier and a glass batch identifier, which is not offered as a rule.
Glass comes in infinite variety and just making two batches with the same optical performance is an art. The leading optical glass makers are Schott, part of the Zeiss Stiftung, HOYA and and Ohara, plus others, with new entrants in China especially. Each firm offers catalogs of various types of glass, many of which are comparable between suppliers, so Leica might use glass from any of the major suppliers, changing from one to another for the same binocular model on a different production run, depending on price or delivery.
As the optics designers have considerable choice of how to get the desired result, the specific glass type used is a tradeoff, high index glass is more expensive or harder to work with, but may be cheaper than adding another lens to get the same optical performance.
At the high end, Kowa has become the leader in building scopes with pure fluorite crystal lenses, a material with superior optical properties, but a nightmare to shape, as it is very brittle. Aside from that, it also dissolves in water, so keeping it sealed is essential. No other firm has embraced this material as much as Kowa, instead they chose to use fluorite glass, such as Ohara's FPL-53, which is less trouble to work with while still almost as good optically.
Afaik, no one offers fluorite crystal lenses in binoculars, so Kowa's new 553 travel scope is the only small aperture optic with that material on the market. Binoculars use fluorite glass formulations instead for their ED glass, but that leaves open a wide range of choices and qualities.
I don't know how one would find out what types of glass were used in any specific binocular model, especially as there are usually a dozen or more lenses involved, each of which may be a different glass.
In sum, it is difficult to draw firm conclusions about a binocular from the type of glass, whether ED or not.
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Old Thursday 6th December 2018, 07:21   #4
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Hi MUHurd,

Skilled optical designers have been making low dispersion objectives for at least 150 years, but the new generation of low dispersion glasses makes their job easier. However 'ED" has somewhat become a marketing tag and no doubt various low grade, low performance glasses that barely meet the ED specification have found their way into cheaper models, judging by the results. Most glass manufacturers produce their own version of the Abbe diagram placing their glasses in the various categories shown on this Wikipedia page. https://en.m.wikipedia.org/wiki/Abbe_number The FK category in the bottom left hand corner is the home of ED glass. You will see they cover a wide range of dispersion values. There is a more detailed version and discussion here.
https://www.telescope-optics.net/des...t_achromat.htm

Very few manufacturers actually reveal the detail of their optical designs. Yes Kowa uses Fluorite crystal in it's scopes, and one or two others mention Schott, but Ohara and Hoya make comparable glasses, which also have been mentioned from time to time. Keep in mind that the CA you see is the sum of all the components and using ED glass for one or two high performance ED lenses will not guanentee CA free viewing.

Just to confuse the matter, and least one major manufacturer appears to have introduced more a sophisticated design component to improve CA control and called it "HD" to distinguish it from their more basic "ED" models. Unfortunately HD is technically meaningless and used rather indiscriminately by the industry.

David

Last edited by typo : Thursday 6th December 2018 at 07:28.
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Old Thursday 6th December 2018, 08:05   #5
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The dispersion values only express the ratio of the glass refractive index at two wavelengths, which is a useful metric, but won’t be a perfect description of the refractive index at all wavelengths, especially as the refractive index of all glasses changes rapidly in the blue/UV. The design of the optics plays as much a part in the performance, with most designs using spherical figured components as they are the easiest to make to high tolerances. Also the tolerance of the designs to variation in the actual glass nominal performan (making glass is basically a witches brew of boiling sand) and to errors in the figure of the optical components. It’s pretty amazing what we can make, enjoy the view!

Peter
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Old Thursday 6th December 2018, 10:10   #6
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Peter, it is incredible what those with the know-how are able to take raw materials and make these fine optical instruments.
When I saw that TYPO mentioned that this perfecting of optical lenses has been a battle or a search for 150 years, it just makes me look upon it with awe. It makes me sit back and ponder how in the world they were able to do it and how they figured out that there was something superior that could be made if they just worked at it a bit longer. Lord Have Mercy, what geniuses we had in our past that helped move society and moreover, science ahead by leaps and bounds. Without the chasing perfection in optical glass, who knows how our knowledge of space, astronomy and even medicine would've lagged behind.
Just think about what those brilliant craftsmen of our past had to work with. They had no high powered gas furnaces, no pure raw material to work with and certainly no CLEAN ROOM environments to work in to minimize microscopic particulate contaminating their product and thus ruining it and having to start all over on another batch trying to get better each time they did it.

I asked the original question thinking that there were a couple main suppliers and the bino makers would buy their ED glass from them, thus making these ALPHA binos essentially the same inside.

Thank you all for your help and advice. I'll go nosing around for some of those earlier threads to see what I can learn from them.
Have a good one fellers.

Larry

Last edited by MUHerd : Thursday 6th December 2018 at 10:12.
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Old Thursday 6th December 2018, 11:37   #7
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Hi,

there is quite a few different kinds of ED glass - for the magnifications used for binoculars their usefulness is a borderline case and the differences will not visible. After all there is a lot of binoculars with decent CA and without ED glass.

For spotting scopes and astro telescopes this is different - they operate at higher magnifications and there differences of the ED and partner glass can be readily seen.

Joachim
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Old Thursday 6th December 2018, 15:33   #8
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Very informative! Thanks MUHerd and those who gave such thoughtful replies.
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Old Thursday 6th December 2018, 17:02   #9
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Hey all,

Something I have been curious about since I started reading up on Bino specs is the subject of ED Glass.

Now I don't know all the specs, coatings and technical jargon associated with this glass, but I would still like to know more about it. I know that all of the "Alpha Binos" list in their specs as having ED Glass. What I'd like to know is whether all of these ED Glass lenses and prisms are created equal. Is the ED Glass in the ZEISS binos the same as the ED glass in a set of Swaro's or Tract Binos or the many others that are said to have ED Glass in them?

I'd love to be able to look thru a set that has the best ED glass and compare them to my Pentax DCF HRII 10x42. I'm pretty sure I have never had the pleasure to use a set of binos with ED glass in them. I know I'd sure like to try a set and just see how they maintain their lofty platforms that they have attained.

Can anyone explain this to me and hopefully helping me to understand why these binos are so expensive and what goes into making a set of these ED Glass Binos.

Help me "see" what is present in these binos that enthusiasts are willing to shell out a lot of money to get the very best money can buy.

In NO WAY am I slamming these sets of ALPHA binos or complaining on their prices. The best comes with a price tag. I'm happy that there are people that have attained a level of success and love their hobby to such an extent that they will buy the best gear that they can possibly get.

Please explain ED glass from these various companies please.

Have a good week.
MUHerd
As long as there are people with money to waste¬—and the inexperience to waste it—there will always be people willing to help them waste it. Such is the “alpha” concept. Who can create a standard for “Alpha”? My best birding glass is NOW an Alpha. BUT, when I bought it, it was just a really good bino. Opinion, not facts, made the difference. I have seen MANY non-ED binoculars that were head and shoulders above so many with “ED” splattered on the backplate. The power of suggestion is better than some realize.

Finally, ED means Extra-low Dispersion and there are several glass types and configurations to accomplish that. Just how much? Very few people look into that.

Bill
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Old Thursday 6th December 2018, 17:07   #10
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https://www.edmundoptics.eu/resource...optical-glass/
For even more. Optical designers will probably use the actual fitted refractive index and transmission data to allow them to select between the infinite number of potential trade offs to result in a high performance cost effective, repeatable to manfacture optic. To think that much was done before the invention of the laser and computer, which have helped in the measurement of design work we now take for granted.

PEter
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Old Thursday 6th December 2018, 17:10   #11
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“Facts, not opinions”.... the carved-in-stone motto of the Kirkaldy Testing Museum https://en.m.wikipedia.org/wiki/Kirkaldy_Testing_Museum and of all good Metrologists!
:-)

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Old Thursday 6th December 2018, 17:12   #12
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As I see it, each piece of glass in its place in the optical train needs to have a defined set of optical characteristics. Multiple glass makers are capable of producing glass with the desired specifications. As long as the standards are met it likely does not matter if the corresponding piece of glass in each barrel are from the same maker or not. If you need to up the optical quality, then it may create a change in the quality needed throughout the system. For instance the Tract Toric recently changed from its original design, to the new Tract Toric HD with "Schott HT glass". The question becomes whether or not the Schott glass used has different characteristics than what was in the original release? Probably does not matter enough to notice in real world use. The marketing perception sure changed in the view of many.

ED glass came to users awareness due its ability to control color fringing. That became a big deal, and so did the term ED glass. While its meaning can be largely a marketing concept, ED glass is like any other glass in that it has to have the required optical characteristics needed for it to function properly in its place in the design.
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Old Thursday 6th December 2018, 17:38   #13
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As I see it, each piece of glass in its place in the optical train needs to have a defined set of optical characteristics. Multiple glass makers are capable of producing glass with the desired specifications. As long as the standards are met it likely does not matter if the corresponding piece of glass in each barrel are from the same maker or not. If you need to up the optical quality, then it may create a change in the quality needed throughout the system. For instance the Tract Toric recently changed from its original design, to the new Tract Toric HD with "Schott HT glass". The question becomes whether or not the Schott glass used has different characteristics than what was in the original release? Probably does not matter enough to notice in real world use. The marketing perception sure changed in the view of many.

ED glass came to users awareness due its ability to control color fringing. That became a big deal, and so did the term ED glass. While its meaning can be largely a marketing concept, ED glass is like any other glass in that it has to have the required optical characteristics needed for it to function properly in its place in the design.
So many folks don’t understand that when it comes to optical engineering, the foot bone is connected to the head bone and when you FIX one aberration—to a tolerable level—you might be MESSING UP two or three others. People who want to play in that arena should really spend some time getting to know at least some of the essential 3rd order aberrations and what makes each grow and shrink.

Bill
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Old Thursday 6th December 2018, 18:07   #14
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... Optical “whack a mole”. I’d be interested to see what might happen if you gave of the newfangled unsupervised machine learning doodads a copy of the Schott catalogue and a copy of zemax.... see what new design concepts it could come up without any optical design history baggage. Might result in some really novel designs. Make a good PhD project.

PEter
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Old Thursday 6th December 2018, 19:30   #15
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... Optical “whack a mole”. I’d be interested to see what might happen if you gave of the newfangled unsupervised machine learning doodads a copy of the Schott catalogue and a copy of zemax.... see what new design concepts it could come up without any optical design history baggage. Might result in some really novel designs. Make a good PhD project.

PEter
It doesn’t matter; people would stay away from it in droves! It would cost too much. I bought my Zemax and Zemax-EE directly from Ken when it was less than $1,000 but haven’t even turned it on for over 10 years. And now that I am iMac based, I can’t even run it. Using it from 1991 to 2014 was an invaluable learning experience.

Bill
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Old Thursday 6th December 2018, 19:36   #16
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Now, lets talk coatings, are they all the same ?

Jerry
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Old Thursday 6th December 2018, 20:01   #17
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Now, lets talk coatings, are they all the same ?

Jerry
No. When you go from mag fluoride to multicoatings you can gain about 13% in light transmission. Once in the realm of multicoatings from industry leaders, few people can see a difference in coatings. There are MANY other factors that few people think about. So the increase is accredited to coatings and posts flourish to nail it down as fact ... when it is not.

There ARE differences the average observer CAN see. But almost never in the same league of binoculars.

The truth is incontrovertible. Malice may attack it. Ignorance may deride it. But in the end, there it is.” — Winston Churchill (attributed)

Bill
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Old Thursday 6th December 2018, 20:22   #18
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And much that you can’t see.. a whole new area of science opened up due to a the low scatter “nano magic” optical coatings a commercial camera lens company uses....
http://www.dunlap.utoronto.ca/instru...ion/dragonfly/

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Old Thursday 6th December 2018, 21:11   #19
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...Can anyone explain this to me and hopefully helping me to understand why these binos are so expensive and what goes into making a set of these ED Glass Binos...
What makes a bin a superb binocular (based on performance) or "alpha" (=prestige brand) is not ED glass (of one type or another), but rather its optical design (including the numbers and shapes of component lenses), mechanical design, precision of manufacture, quality of materials, and the company's history. It isn't the ED glass that makes these bins expensive, but rather the expense of R&D, inspired engineering, precision manufacture, European salaries, and the premium commanded by brand prestige. Some alphas lack ED glass, but they are still expensive, and plenty of cheap bins are available with ED glass.

--AP
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Old Thursday 6th December 2018, 21:25   #20
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What makes a bin a superb binocular (based on performance) or "alpha" (=prestige brand) is not ED glass (of one type or another), but rather its optical design (including the numbers and shapes of component lenses), mechanical design, precision of manufacture, quality of materials, and the company's history. It isn't the ED glass that makes these bins expensive, but rather the expense of R&D, inspired engineering, precision manufacture, European salaries, and the premium commanded by brand prestige. Some alphas lack ED glass, but they are still expensive, and plenty of cheap bins are available with ED glass.

--AP
Succinct and accurate.

Bill
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Old Thursday 6th December 2018, 22:42   #21
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When i worked in recording studios, and later taught others, i had an expression that 'the strength of the line is in its weakest component.' An audio signal, flowing through an audio chain towards the ears, could have the finest microphones, pre-amps, eq etc. but be let down by one cheap plug.
Thus i suspect it is with optics, and most other things. The light path has to encounter the finest throughout, including the engineering. For this, much research and development of precision machinery and equipment will be necessary. Hence - not cheap. ED glass is fine, providing it doesn't pass through a bottle-top 2 inches further up the line.
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Old Thursday 6th December 2018, 23:41   #22
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“Facts, not opinions”.... the carved-in-stone motto of the Kirkaldy Testing Museum https://en.m.wikipedia.org/wiki/Kirkaldy_Testing_Museum and of all good Metrologists!
:-)

PEter
Truly wonderful!
Would that this sentiment were more widely implemented.
Sadly it is totally the opposite of marketing/spin which dominates current optical advertising. Just check how many facts you can find in a current binocular brochure.
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Old Friday 7th December 2018, 00:14   #23
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It will probably always be 75% opinion in binocular selection. Facts come from the design specifications and results from the optical lab bench. How two people see the same binocular is always going to be a subjective affair. Lab tests say nothing about ergonomic, let alone personal perspectives on brand recognition and perceptions of company history. Even a review site like Allbinos tries to make objective rankings out of various subjective impressions.
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Old Friday 7th December 2018, 00:50   #24
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It will probably always be 75% opinion in binocular selection. Facts come from the design specifications and results from the optical lab bench. How two people see the same binocular is always going to be a subjective affair. Lab tests say nothing about ergonomic, let alone personal perspectives on brand recognition and perceptions of company history. Even a review site like Allbinos tries to make objective rankings out of various subjective impressions.
No argument on any of this.
I'd just be a lot happier if there were a factual supplement added to the sales document, which specified the optical parameters in some verifiable fashion. Right now, we have nothing at all.
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Old Friday 7th December 2018, 01:00   #25
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No argument on any of this.
I'd just be a lot happier if there were a factual supplement added to the sales document, which specified the optical parameters in some verifiable fashion. Right now, we have nothing at all.
If people knew the FACTS, those who like to brag about their Alpha binocular, talk about their “vintage” binocular, or try to make comparisons among the world’s finest instruments they are not prepared to make, they probably wouldn’t buy any.

Bill
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