Big Newb Question: Specifically, why coatings cost $$

[GeneralEverything]

Alright, so, this is where I show my true colors of novice. However, I want to know for fun: what specifically costs more about high end coatings? Are they made with powdered hen's teeth, blood of unicorns, and platinum/osmium alloys? Is the cost of the raw materials so high? Is the volatility/dangerous characteristics of the coatings such that you have to pay an arm and a leg? The difficulty of achieving the right chemical mixture? The application so very difficult? The research and development? I understand the armor, collimation, ergonomics, bak4, HD, XD, ED, tolerances, name recognition, and all the other raw materials for price consideration. I also understand the price differentials in factory location. However, I've heard people say that you pay for the coatings. So, do enlighten me, as to what exactly makes the coatings expensive; or if it's just that the companies have agreed not to release binoculars with X coating for below X dollars? Not trying to cause trouble, but being a geek, I have to know the reason for everything.

[Surveyor]

GenEv;

The cost is mostly in the time it takes. A lot of the high end optics using multi-coatings can have 64 layers or more. I think most use a technique of vacuum-vapor deposited coating and we are talking thickness in the parts of a micron range.

See the simple explanation in this link.
http://rick_oleson.tripod.com/index-166.html (http://rick_oleson.tripod.com/index-166.html)

Have a good day.
Ron

[Tero]

Hey, we have never been to the lens factory, so we do not know. But they say they put on all these coatings and we believe them.
Coatings are needed for problems of all sorts
http://en.wikipedia.org/wiki/Aberration_in_optical_systems
http://en.wikipedia.org/wiki/Chromatic_aberration

I have them on my eye glasses to reduce glare
http://rick_oleson.tripod.com/index-166.html
For example, if you want to apply 5 layers, you would need 5 different materials with indices of roughly 1.1, 1.2, 1.3, 1.4 and 1.5 to span the range between air (1.0) and glass (1.6). From here on, the process is the same as with the single coating, except that each layer is made a slightly different thickness from the others, with the thicknesses selected to correspond to several different wavelengths within ...
http://en.wikipedia.org/wiki/Anti-reflective_coating
The closest 'good' materials available are magnesium fluoride, MgF2 and...

[Keith Dickinson]

I have been in a clean room where multi-layer coatings are applied to spectacle lenses. The coatings machine has a vacuum chamber which maintains an extremely high vacuum for the coating process, which is a vaporisation process. Exactly what was being vaporised we never found out, trade secret. The thing was that if there are any problems with the process then the entire chamber full of lenses are usually scrap. I think there were about 30 or so lenses in the chamber at one time, but there may have been more as we were not shown the inside of the chamber, just one of the mounts that the lenses are placed in. I would imagine that the fail rate for scope and camera lenses would be higher as the coatings have to be much more tightly controlled.

[GeneralEverything]

Thanks for a couple explanations. I have been able to grasp why coatings are necessary, what they do, etc., I just wondered what justified the companies to put such a hefty premium on the different coatings.

So far, it seems there is agreement that actual application of coatings is a time-consuming, difficult process, as well as the hardware costing an arm and a leg. That's good to know. So, the 64 application coating thing, sorta like the cost of making samurai swords- repeatedly folding the steel many, many times, so as to distribute the carbon evenly. Interesting stuff. I've read about zeiss and fluorite, and the dielectric coatings, and all that fun stuff, but I never saw an explanation as to why this would be orders of magnitude more expensive than ones without such coatings.

More explanations are welcome, but it seems that I've gotten an answer. I didn't imagine applying the coatings would be such a fraught process, but that's why I'm new here, and you guys are the experts.
Best Wishes,
GenEv

[ThoLa]

Alright, so, this is where I show my true colors of novice. However, I want to know for fun: what specifically costs more about high end coatings?

It is actually the time (working hours) of highly qualified engineers who develop these systems.

Research and development is very costly, and in technology it has a limited shelf-life, so to speak, as the competitors are going to catch up sooner or later (often by capitalizing on someone else's costly efforts!).

Once you know how to accomplish the feat, it's usually an easy run.
That's why companies (top end makers in particular) never give away technical details (secrets!), except for those things that can be worked out easily by competitors.

Tom

[BirderSean]

I understand the armor, collimation, ergonomics, bak4, HD, XD, ED, tolerances, name recognition, and all the other raw materials for price consideration.


I'd like to know the difference between bak4, HD, XD, and ED.

any good links for that?

[ThoLa]

I'd like to know the difference between bak4, HD, XD, and ED.

any good links for that?

Bak4 is a special type of glass containing barium ions, used for optical purposes.


HD, XD, ED are non-specific terms that do not tell anything really.


Mind: NONE OF THESE OR ANY OTHER AKRONYMS USED BY MANUFACTURERS TELL ANYTHING (!) ABOUT THE Q U A L I T Y OF THE GLAS !!!

The optical (physical) properties of optical glass depend very strongly (!) on the cooling regime of the melt from which the glass is made! Fancy names do tell nothing!

Tom

[stabor]

I quote from Optical Instruments for the Observation of Nature by Klaus-Dieter Linsmeier (basically a Swarovski publicity piece), p. 56:
To achieve vaporization, the [coating] materials are placed in crucibles heated by electric coils. In the case of coatings with a high melting point such as titanium, however[,] the crucible itself could then sustain damage. For this reason, the trend is increasingly towards vaporizing coating substances with an electron beam. ...
Given that the thickness of the coating must be adjusted with extreme precision, the question arises as to the method used to determine when it has been reached. The optical component carrier features an integral oscillating crystal, which has a mass-related natural frequency. As a result of the coating forming on the crystal itself, its mass changes, and, in turn, its measurable natural frequency. The optimum quality of the coating is ultimately determined by the measurement of light transmission by a flat glass specimen, which was also coated together with the lenses.

[Kevin Purcell]

ED does have a special meaning: it means the Abbe number is > 90 but it's been somewhat abused.

The others XD, HD, etc are all marketing terms.

Take a look at this post.

http://birdforum.net/showthread.php?t=124820&highlight=Abbe+number

The particular glass types can be described by their Abbe number and their refractive index and grouped by these properties (which usually reflect how they're made).

http://en.wikipedia.org/wiki/Abbe_number

http://en.wikipedia.org/wiki/Image:Abbe-diagram.png

BK7 is a particular type of borosilicate crown glass (the BK is from the German name).

BaK4 is a barium crown glass with lower Abbe number (more dispersion) but higher refractive index so it's preferred in prisms to BK7 (but not in lenses!) allowing a large light cone to undergo total internal refraction in the prism.

There are a couple of ED glasses mentioned on the Abbe chart (both Schott glasses) but there are others from other makers. As Henry points out in the thread referenced above an ED glass has become pretty cheap in China and is now starting to be widely used.

[ThoLa]

.... an ED glass has become pretty cheap in China and is now starting to be widely used.

And, as has been pointed out, we know nothing about its QUALITY !

It's probably low to lousy.

[Tero]

It comes down to how well can you see the differences. The binocular in your hand has to sell itself to you. Coatings or ED glass will not make it a good binocular necessarily.

[Kevin Purcell]

And, as has been pointed out, we know nothing about its QUALITY !

It's probably low to lousy.

And that would explain why the Promaster ED and the Hawke ED are so lousy in their view.

Wait, they're not lousy. They're a notch below the Big 4.

So we do know something about it's quality.

Chinese ED glass is not lousy. It's widely used in a range on non-lousy products including a bunch of astro gear.

Seriously making decent optical glass is not rocket science. It takes a little care and attention (keeping to pot stirred, measuring the concentration of the components, taking glass fromcenter of the pot and measuringit's properties before shipping it). The Chinese these days are easily capable of doing that.

Speculating on something you've never used is never helpful.

[ThoLa]

Seriously making decent optical glass is not rocket science.


Rocket science: a piece of cake. All you need to do is get a ruler, do some simple arithmetics with Kepler's laws, fill up the propellent, then pull the trigger. Off you go. Even the Chinese can do it.


How do you know so much about glass making?
Are you materials scientist?

T

[Kevin Purcell]

So that's an amusing rant but we actually already have the proof that they can build very good bins. Not perfect but very good.

PhD chemist (one of my many hats) plus you can actually learn about this stuff if you read about it. Not an expert but the more you understand the more you can see what is marketing fluff and what is real.

Perhaps the hardest test of glass quality in a roof prism is in the roof prism itself. See the Swaro 1991 binocular design paper I posted a link to some time back. In addition to very precise mechanical requirements (the roof edge angle has to be very sharp and correct to 10 seconds or less) you also have to worry about inhomogeneities in the prism glass because the prism acts essentially as an interferometer (splitting and recombining the same light along two different paths) so imperfections (changes in refractive index and scattering centers about the size of wavelength of light) can reduce the quality of the view.

It's clear from the ED bins they're shipping that the Chinese glass and roof prisms makers have a grasp of how to make very high quality glass and components.

[Tero]

Ah, but how did you do in inorganic chemistry? It's a less popular field. I'm "organic" here, and no, we do not do chemistry with manure as one California woman assumed. But glass was not on my undergrad curriculum. And I only got the one hat, in 1980. Probably expired by now.

[NWBirder]

And that would explain why the Promaster ED and the Hawke ED are so lousy in their view.

Wait, they're not lousy. They're a notch below the Big 4.

So we do know something about it's quality.

Chinese ED glass is not lousy. It's widely used in a range on non-lousy products including a bunch of astro gear.

Seriously making decent optical glass is not rocket science. It takes a little care and attention (keeping to pot stirred, measuring the concentration of the components, taking glass fromcenter of the pot and measuringit's properties before shipping it). The Chinese these days are easily capable of doing that.

Speculating on something you've never used is never helpful.


I finally got a chance to view through a pair of Promaster Elite ELX through the wallet of my friend. :) The image quality is quite impressive. They are not lousy at all, as opposed to someone who wants us to believe. For $500, it is definitely worthy every penny comparing to those more expensive big4 offerings.

[ThoLa]

So that's an amusing rant but we actually already have the proof that they can build very good bins.

That's wonderful.
If you have that proof in terms of measurements, share it with us.

Or provide a reference where these numbers can be found.

I like to see the evidence of how good they are.

Thank you for your help.
Tom

[ThoLa]

PhD chemist (one of my many hats) ...

Hats off!
That means you ought to be able to read phase diagrams and have learned something about mixed-phase thermodynamics, phase transitions, kinetic inhibition, and so forth.
So you should be able that making high quality optical glass is - contrary to your own claims - is anything but trivial, and that it is indeed quite a feat to prevent the formation of any anisotropies during the cooling of the melt while sending it down the metastable dead-end road of solidifying into a glass.

In conclusion the silly statements about the triviality of the problem of making optical varieties of the highest quality must inevitably be attributed to an exquisite sense of humour. LOL. :king:

T

[Tero]

Tom, I know this much. Glass does not solidify. It is in fact a "glass". I have some organic materials that behave like that. There are no crystals.

[OwenM]

That's wonderful.
If you have that proof in terms of measurements, share it with us.

Or provide a reference where these numbers can be found.

I like to see the evidence of how good they are.

Thank you for your help.
Tom
Since you want to bash something you say you know nothing about, maybe you should be the one to step up with proof, rather than asking someone else to.
I'd like to see the evidence of how bad they are.
Thank you for your help.

[ThoLa]

[QUOTE=Tero;1343526]Tom, I know this much. Glass does not solidify. ..../QUOTE]

Wow!
That's good to know. I shall henceforce take great care to always keep my binos precisely levelled to prevent the lenses from leaking. ;)
It would spoil my day to see all that expensive optical glass percolate into the soil.

Fortunately the drinking glasses in the kitchen cupboard do not know much about this topic (they are made of LI glass*), so they have stayed nicely solid. B (:
Up to know that is ......... :eek!:


*Low Intelligence glass

[Tero]

No only that, your glass in your windows, in a million years, will dribble down so it will be only 1mm thick at the top and a blob at the bottom. ;)

[dantheman]

No only that, your glass in your windows, in a million years, will dribble down so it will be only 1mm thick at the top and a blob at the bottom. ;)

I expect some kids will have smashed them long before then . . .

The oldest glass in buildings around (400 years maybe? - see I know nothing really) tends to be a lot thicker at the base than at the top, definately in the mm range rather than microns etc . . . but then do some metals do this too??

(Are we still discussing coatings by the way?? ;) )

[ThoLa]

No only that, your glass in your windows, in a million years, will dribble down so it will be only 1mm thick at the top and a blob at the bottom. ;)

That's a warranty issue then, isn't it?
(quality glass comes with a life-time warranty, doesn't it?)

For the time beng I have put a bucket and a towel under each windowsill
to wipe up the mess (novel chores all the time). ;)


Tom

[ThoLa]

. . . but then do some metals do this too??


The experiments are still running. It takes a while to collect the data for the first million years. ;)

(Seriously speaking (for a change)):
No, metals don't show this behaviour. At least they are not supposed to do it. They consist of crystals (proper solids, according to Tero;)) which are truly rigid. Glass - as Tero as pointed out - can be thought of as a super-cooled liquid of (nearly ... ) infinite viscosity (a popular physico-chemical model). But of course it is solid (!). It is for all practical purposes (unless you build a cathedral;)), and according to the defining criteria for solids that are used in many textbooks of physical chemistry and solid-state physics! As an amorphous solid it shows some pseudo-liquid behaviour.


Let's discuss coatings again:

trench coat-ings
fur coat-ings
leather coat-ings
...

Tom