Various Types of Optical Glass Explained

[Ezana4CE]

I found this information useful when shopping around for glass whether it be riflescopes, binoculars, spotting scopes, etc. I would read product descriptions and not really understand what some of the finer details of glass types and glass coatings are. Me being curious, I began looking for answers. I found the information in the following link to be very helpful. The photographs and diagrams are very helpful in understanding some of what's explained.

Optical Glass For Binoculars - What Is ED Glass, Crown- or Flint Glass

Optical glass used binoculars is crucial to image quality. Combining Crown glass and Flint glass in lense systems reduces aberration and provides clear and sharp vision

bestofbinoculars.com

“How to Choose Field Scopes: Comparison of ED glass and ordinary lens”

Comparison of ED glass and ordinary lens | Sport Optics Guide -Fieldscopes- | Nikon Consumer

Glass Coatings Explained (check out the source reference link to Schott at the end of the article):

What is the Binoculars Lens Coating for?

Without coatings, binoculars with multiple lenses would be virtually impossible to use. Binoculars lens coating improve transmission and image quality.

bestofbinoculars.com

As I come across more information or when I take time to dig into my bookmarks I may add more information to this thread.

edit: 01/07/25
“March Scopes is the Pioneer in the use of ED lens, Super ED lens, Temperature anti-drift lens system. Classification of March Scopes by lenses”

March Scopes is the Pioneer in the use of ED lens, Super ED lens, Temperature anti-drift lens system. Classification of March Scopes by lenses | Quality, Factory | MARCH Scopes | DEON Optical Design CorporationMARCH Scopes | DEON Optical Design Corpo

MARCH Scopes Official Site

marchscopes.com

​

Source of above photo: https://marchscopes.com/news/10054/#:~:text=ED stands for Extra-low,magnification and high-end scopes.

Lens Coating Longevity - This is an area that I know very little about and I'm still learning. As new scope manufacturers emerge offering better quality for a lower price, these products are often produced overseas. In my reading, older scopes with glass produced in Germany and Japan seemed most desired by glass aficionados. Glass producers from these countries have been touted for their quality. More recently it seems that glass produced in the Philippines is second rate, but of reasonable quality for good mid-tier scopes (Sightron is a brand that comes to mind with good glass produced in the Philippines). More recently Athlon Optics has apparently amassed a huge following with several scopes in their line manufactured with Chinese glass that shooters all over the globe post on myriad online platforms about the bang for your buck quality from glass, reticles, to turrets and over-all construction. Since this is a glass thread, I began to wonder, What makes Athlon glass so good? When I visited their site, a lot of the descriptions lead me to believe it is the coatings applied to the glass. Looking at their lower-level budget offerings: the Talos and the Argos. On the Talos, Athlon describes their coatings as, "Fully multi-coated" and that "Athlon Optic's fully multi-coated glass gives you better light transmission with optimum brightness and true color across the entire light spectrum." What exactly does this mean? Which coating processes are used? What specifically are the benefits of each coating material? Do all of the coatings work well in conjunction with one another? Athlon boasts of their coatings on the Argos as "XPL coating" that is "A protective coating that gives you extra protection on the exterior lenses to prevent the scope from enduring dirt, oil, and potential scratches." An extra coating in addition to what? Most importantly, how long do these coatings last? Have there been tests to determine any duration of effective lens coating's durability? Are those results published? Can consumers access that data?

Source of coating quote on the Argos line: https://athlonoptics.com/product-category/rifle-scopes/athlon-optics-argos-btr-gen2/
On Talos line: https://athlonoptics.com/product-category/rifle-scopes/athlon-optics-rifle-scopes-talos-btr-gen2/

Some questions to ponder:
1) What are the most desirable and essential rifle/pistol scope glass coatings?
2) Is one particular process of applying these coatings superior producing better quality?
3) How does the consumer identify if he manufacturer is using quality materials for their glass coatings?
4) What differentiates top-tier glass from mid-tier glass? From budget glass?
5) How long do optical coatings last on top-tier glass before exhibiting significant deterioration compromising image quality or protective properties?

I found this article interesting and somewhat helpful , although it is focused upon camera glass.

How long do lens coatings last? Expert Tips and Advice |

Learn about how long do lens coatings last. Discover factors impacting their lifespan. Maximize their longevity with expert tips and advice.

cameralenshub.com

 

[rcs9250]

Ez, thank you for posting. Excellent articles. As I read I found myself looking up a lot of optics related words so that I had a good understanding of what I was reading.
I was in Cabela’s once and looked through several different brands of binoculars. Starting at “budget’ and then working up to the “ain’t no way” binoculars. Quite amazing the difference.

I’m going to guess that budget will generally dictate what a buyer will end up with. Can I get by with a Civic or do I need an Audi or is a Lambo the only thing that will satisfy me?
One thing a co-worker told me a long long time ago about selecting binoculars.
You divide the objective diameter by the magnification number and you need to have a number larger than five. For instance, take a common 7x35 binocular. The math equals 5. If the answer in a combination is less than 5, light transmission will be less. In that case they might be better for bright or midday use. I don’t know if that still holds true with todays advanced coatings.

Lots and lots of hunting magazines always have pictures of hunters “glassing” with Swarovski and other high end binoculars. The higher the price the more they weigh. Not everyone has a sherpa for gear like Craig Boddington.
I have a decent pair of 8x42 Vortex I believe they are that I use. But typically I have an 8x40 monocular that I use when squirrel hunting that I’ll use for looking at birds and things rather than swinging my rifle around looking through the scope. I like the monocular because it’s light weight and it doesn’t take much room in my pocket. To each his own.

Edit: Had ocular rather than objective in paragraph 4.

 

[jarmstrong]

rcs9250,,, did you mean the objective lens size, rather than the ocular diameter?
must be the "ocd" in me,
I am pleased/satisfied with my Athlon Midas 10x42 even though they fall under the quotient being 5

had a 'low priced' mono, gave them to a friend who works a pumping /dredge at a sand pit, if they fall into the water, they are history,,, would not take a quality glass out there, to be abused. working grade is is fine for that job

 

[rcs9250]

rcs9250,,, did you mean the objective lens size, rather than the ocular diameter?
must be the "ocd" in me,
I am pleased/satisfied with my Athlon Midas 10x42 even though they fall under the quotient being 5

had a 'low priced' mono, gave them to a friend who works a pumping /dredge at a sand pit, if they fall into the water, they are history,,, would not take a quality glass out there, to be abused. working grade is is fine for that job

You are correct. I will edit. Thank you.

 

[rcs9250]

rcs9250,,, did you mean the objective lens size, rather than the ocular diameter?
must be the "ocd" in me,
I am pleased/satisfied with my Athlon Midas 10x42 even though they fall under the quotient being 5

had a 'low priced' mono, gave them to a friend who works a pumping /dredge at a sand pit, if they fall into the water, they are history,,, would not take a quality glass out there, to be abused. working grade is is fine for that job

Jarmstrong, yeah my co-worker told me that quite a while ago. Most likely coating and glass advancements may have changed that a bit.

 

[Ezana4CE]

Ez, thank you for posting. Excellent articles. As I read I found myself looking up a lot of optics related words so that I had a good understanding of what I was reading.
I was in Cabela’s once and looked through several different brands of binoculars. Starting at “budget’ and then working up to the “ain’t no way” binoculars. Quite amazing the difference.

I’m going to guess that budget will generally dictate what a buyer will end up with. Can I get by with a Civic or do I need an Audi or is a Lambo the only thing that will satisfy me?
One thing a co-worker told me a long long time ago about selecting binoculars.
You divide the objective diameter by the magnification number and you need to have a number larger than five. For instance, take a common 7x35 binocular. The math equals 5. If the answer in a combination is less than 5, light transmission will be less. In that case they might be better for bright or midday use. I don’t know if that still holds true with todays advanced coatings.

Lots and lots of hunting magazines always have pictures of hunters “glassing” with Swarovski and other high end binoculars. The higher the price the more they weigh. Not everyone has a sherpa for gear like Craig Boddington.
I have a decent pair of 8x42 Vortex I believe they are that I use. But typically I have an 8x40 monocular that I use when squirrel hunting that I’ll use for looking at birds and things rather than swinging my rifle around looking through the scope. I like the monocular because it’s light weight and it doesn’t take much room in my pocket. To each his own.

Edit: Had ocular rather than objective in paragraph 4.

@rcs9250 No problem. I can relate to some of what you're saying. I didn't understand all of the terminology either, but I'm slowly catching on. When looking for binoculars (binos) I learned that the type of prism is also important as well as the glass. After reading some articles I learned that the coatings also matter, but the article I posted here succinctly explained why coatings for glass used for hunting are important. Because I hunt in the woods, I often hunt in low light situations (in addition to sunset and sunrise for various game animals) then the coatings affecting reflection and light transmission are important to me in addition to objective diameter size for "light gathering." There is so much to learn it is easy to get overwhelmed. For me continuing to read over a long period of time has helped some. Then having access to forums and individuals with greater understandings and knowledge bases also helps.

As a consumer, understanding some of these concepts helps to prevent the bumbling around and aimless buying a bunch of glass that isn't suited towards specific applications or are just a waste of money. So I figured, "Why not share this info?" since it has helped me tremendously. I put some of this newfound information to the test in a recent scope purchase. I'll see how it serves me since I had good luck when I bought my Vortex binos after doing some reading on binoculars. As for the price-point corresponding to quality, I can't speak to that so much as I can to practical application. I don't own any high-end glass, but let me use my spotting scope for example. It's a cheap Simmons spotter that I bought used for less than $100.

Here's a photo taken just to document the range I was shooting from. This is from a Leica rangefinder. I specifically sought out this brand for the glass.

Now after I shot a group, I looked through that Simmons spotting scope and didn't have an issue seeing the holes. Too bad I didn't take photos through the spotting scope. It is a PITA to hold a phone steady to align the camera lens with the ocular lens on the rangefinder or spotter.

I can see holes in paper at 100+ yards with my spotting scope (.25 caliber being the smallest I've shot to 100 yards so far). I don't use spotters in the woods. I will either use binoculars, a rangefinder (on the rare occasion that I bring one), or my rifle scope to glass. So the glass on the spotter really only needs to serve its purpose in open spaces where I generally choose to shoot. The most I struggle with lighting is shooting west during sunset, later in the afternoon when the sun moves below the treeline, or on overcast days when the sun gets covered by clouds that move intermittently. It hasn't failed me yet so until I hit the mountains on an elk hunt or start shooting 250-500 yards, this little Simmons should do the trick. Same with rifle scopes. I still have a cheap Aim Sports Alpha 6 SFP that has some good looking glass for such a cheap scope. I don't think I've turned into a scope snob, but I like what I like often because it works. I've taken suggestions from others and bought scopes that people fawned over and found myself underwhelmed (Athlon Helos BTR gen 2 comes tom mind here). So I can speak from a little experience in taking time to learn about some of the elements of optics to make better purchases for my needs. I hope that others can utilize some of this information similarly and post information that helped them select the best optics for themselves.

 

[Motorhead]

Really nice glass such a Schmidt* Benders PMII .... you can see a ladybug on a tree leave easily at 2-300 yards.
There image SHARPNESS is so good one kinda wonders and then realizes WHY the U.S. as with many armed forces around the world choose them for precision / sniper applications.

 

[Ezana4CE]

Really nice glass such a Schmidt* Benders PMII .... you can see a ladybug on a tree leave easily at 2-300 yards.
There image SHARPNESS is so good one kinda wonders and then realizes WHY the U.S. as with many armed forces around the would choose them for precision / sniper applications.

@Motorhead One of these days I am going to treat myself to some top-tier glass. I'm thinking something within the $2000 - $3500 range. I have to work my way out and become a better long-distance shot first. I have heard and read good things about Schott glass. I don't know who all of the top tier glass makers are. I've read that German and Japanese glass are desirable. I don't know whole bunch about it. I'm still learning.

 

[Ezana4CE]

This will likely be an ongoing search for information, but I aim to answer some of the 5 questions posed in the 1/07/25 edit of my initial post. I have a decades old scope whose glass has obviously suffered degradation. The glass has some discolored spots on it. Unfortunately I am not qualified to say what they are exactly or what caused these aberrations. What does concern me is preventing or delaying scopes that I currently own from ended up that way.

 

[boscoebrea]

This has been a pet subject of mine for decades.I been "glassing" for over 40years.I need the better binoculars and spotting scopes.Rifle scopes , just need good ones.
Someone may say these binos are good enough,ok for them they are...I want to see the nuances,the pine needles,the birds individual feathers.It costs more money for more detail;yes, indeed, coatings are of special importance, as is the type of glass, and the alignment of the glass; all this perfection takes time and talent.
How important are these factors,my over 15-year-old Swarovski binos are still great,still hold their own with the newer offerings,I do find them a bit heavy and not as easy for me to walk around with as my Nikon 8x32, which are way more handy and almost as good,it is all relative on your needs, wants and $$$$$. I am also a big time audiophile,way a lot of $$$$$ spent, you see it is the same; great"glass" one you see, the other, great audio gear, you hear; Both,it is about the "nuances."

 

[boscoebrea]

Oh, that may be defamation or wrong word ,but glass is not just one piece. It may be 2-4, whatever; in time and heat, the Sun and hot days tend to break down the coating and the "glue" .Keep your optics out of direct Sun, cover them up when not in use....
My face has taken a beating from the Sun,I learned too late how bad the Sun can be to my face

 

[Ezana4CE]

Oh, that may be defamation or wrong word ,but glass is not just one piece. It may be 2-4, whatever; in time and heat, the Sun and hot days tend to break down the coating and the "glue" .Keep your optics out of direct Sun, cover them up when not in use....
My face has taken a beating from the Sun,I learned too late how bad the Sun can be to my face

@boscoebrea This is something I've been reading about on and off for a couple of years. I'm still trying to get a better understanding of it. It seems that extreme heat, high humidity, and very cold temps can affect the coatings. This puts a hunting scope in my region at a disadvantage as far as I can tell. I have noticed defects in what I think are optical glass coatings on an older older budget scope or two. As yes I agree that we must consider all of the glass within these optical systems. I'm most concerned about the ocular and objective lenses considering that they come into contact with dust, water, oils, solvents, and cleaning implements. I usually keep my scopes capped when not in use.

 

[boscoebrea]

Yes, German, Austrian, and Japanese glass.
STORY ABOUT Japanese, they had great glass,WW2 it was destroyed .We, the USA set about helping the Japanese rebuild their country,=glass makers, we send a techncation; I think he was from Kodiak or Bend& Howell, over to Japan to set up their glass-making facilities again....anyhow when you see the gold and black label on the old Japanese glass it is there because it had to pass a bunch of optical tests this man had set up......it is a great read Sorry for my mispellen

 

[Ezana4CE]

Yes, German, Austrian, and Japanese glass.
STORY ABOUT Japanese, they had great glass,WW2 it was destroyed .We, the USA set about helping the Japanese rebuild their country,=glass makers, we send a techncation; I think he was from Kodiak or Bend& Howell, over to Japan to set up their glass-making facilities again....anyhow when you see the gold and black label on the old Japanese glass it is there because it had to pass a bunch of optical tests this man had set up......it is a great read Sorry for my mispellen

@boscoebrea I'm familiar with some of that general history, but that is in interesting detail about the post-WWII glass makers. Do you know much about optical coatings and the processes used to coat optical glass lenses? Or do you know of a sound resource detailing any of this?

 

[boscoebrea]

Some other info. All these hundreds of scope makers, properly90%, glass lens they them from a Few "glass" makers....I say that about all use the same glass for whatever price range scope they are selling,,same glass ,so why does it seem one brand scope is better than the other...I mean, it is the same glass.....it is like this,care...that is the difference between the care and time a scope manufacturer takes to put that scope together and then test it....all this takes more time, but Jesse, some scopes cost more than others using the same glass.yes I just answered that question....and a smart company with more pride in their workmanship will take time to make sure it is right from the get go
We the air gun family help these manufacturers by telling how much we like their scopes......
my ADD has got the best of my and I am truly funky now......sorry

 

[boscoebrea]

Yes, I know about the coating. I will just say that it is time-consuming and helps a great deal in light transmission. A good coating should be higher than 87% at the least.

 

[boscoebrea]

Ezana,it is a great read, and the history lesson will be worth reading.... If you do a search and maybe start with the history of optics, it will be worth it.It is not a short story though,not long either.

 

[Ezana4CE]

Some other info. All these hundreds of scope makers, properly90%, glass lens they them from a Few "glass" makers....I say that about all use the same glass for whatever price range scope they are selling,,same glass ,so why does it seem one brand scope is better than the other...I mean, it is the same glass.....it is like this,care...that is the difference between the care and time a scope manufacturer takes to put that scope together and then test it....all this takes more time, but Jesse, some scopes cost more than others using the same glass.yes I just answered that question....and a smart company with more pride in their workmanship will take time to make sure it is right from the get go
We the air gun family help these manufacturers by telling how much we like their scopes......
my ADD has got the best of my and I am truly funky now......sorry

@boscoebrea Seems to be in alignment with this

Source of above photo: https://www.electrooptics.com/feature/smooth-operators-dark-art-optical-polishing

 

[Ezana4CE]

Yes, I know about the coating. I will just say that it is time-consuming and helps a great deal in light transmission. A good coating should be higher than 87% at the least.

@boscoebrea I was thinking that the transmission of collective coatings of all glass components should be above 96-97% in an expensive top-tier scope. I would think 90% is low for top-tier glass. Are my expectations too high?

Regarding the coatings, there are a few things that interest me. Which materials and chemicals are used for coatings? How do various chemicals in these coatings interact with one another when multiple layers of coatings are applied to the same lens?

 

[boscoebrea]

You are right. Those coatings are a secret and not shared.
I found out this newer friend of mine is an optical physicist. Quite a surprise.
Here is what his company does: It researches new optic frontiers and ways of building better optics. He travels all over the world, selling these new discoveries.I do not like that part.... the new thing is digital eyeballs for blind people, I can't say more,well ok the micro processers from the eye are wired to the part of the brain that sees,,,your eyeball ...will enough of that.....