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Two23
19-Mar-2011, 21:16
I just received a 250mm Imagon (60s vintage with Copal 3?), and have read it's a pretty primitive lens design. Apparently it was coated by Rodenstock from the beginning, something like 1931. I've been discovering that coated lenses are very beneficial to my kind of photography. (I shoot at night using flash, and uncoated lenses flare easily.) What were some of the earliest lenses that were coated, and when did they appear? I especially want to know which ones I might easily find, and are appropriate for my 4x5 Shen Hao. I have a Schneider SA 90mm f5.6 that is monocoated, but I assume it's only from the 1950s or later. It has a PC post (and 3 choices for sync including X and M.) What were the first coated lenses for 4x5?


Kent in SD

GPS
20-Mar-2011, 05:12
Lenses were naturally coated since their origin. Most of the old lenses are - by now- already naturally coated. It was only in the WWI that military people noticed that and started later with the first artificial lens coating. A good proper lens shade has more effect on picture quality than lens coating.

Dan Fromm
20-Mar-2011, 06:02
Kent, as a practical matter lens coating reached the civilian market after WW-II. Coating under vacuum was invented at CZJ in 1934, wasn't commercialized and the patent wasn't published because the process was seen as a military secret.

Why do you think that Rodenstock sold coated lenses before WW-II? Existence of coated pre-WW-II lenses isn't conclusive because after the war it was possible to have old lenses coated.

EKCo started coating lenses for civilians in 1946; not all of the lenses EKCo made in '46 are coated, I have one that isn't. Coating was pretty universal by '50.

Also as a practical matter, nearly all lenses made for large format after WW-II are "modern" types, i.e., well-corrected anastigmats. There are no reasons but nostalgia and budget to prefer lenses from the late '40s through the mid- to late-60s to newer ones, the newer ones are better in all respects.

GPS, lenses are coated for two reasons. To reduce veiling flare and to improve transmission. It was only after coating was invented that modern types with 8 air-glass interfaces were made in quantity for still photography. Or so the story goes. What puzzles me is that in the '30s TTH made a variety of fast 6/4 double Gauss types for cine cameras. What, I wonder, did "Hollywood" know that Leica users didn't?

GPS, re "natural coating," my pre-WW-I CZJ and B&L lenses don't have it. Surely they're old enough.

GPS
20-Mar-2011, 06:18
...
GPS, re "natural coating," my pre-WW-I CZJ and B&L lenses don't have it. Surely they're old enough.

How do you know they don't have the natural tarnish?

Ole Tjugen
20-Mar-2011, 06:27
Some of the early glass types tarnish, others do not. I have an old Schneider Xenar Typ D which has natural tarnish that functions as a coating, but I have never seen an Aplanat with tarnish: It's the wrong type of glass for it.

I have a post-production-coated Rodenstock Eurynar as well as an original uncoated one of the same age. With eight air/glass surfaces, it makes a LOT of difference in flare and contrast.

GPS
20-Mar-2011, 06:33
...

GPS, lenses are coated for two reasons. To reduce veiling flare and to improve transmission. It was only after coating was invented that modern types with 8 air-glass interfaces were made in quantity for still photography. Or so the story goes. What puzzles me is that in the '30s TTH made a variety of fast 6/4 double Gauss types for cine cameras. What, I wonder, did "Hollywood" know that Leica users didn't?

...

Dan, lenses are coated for a multitude of reasons. There are even lenses coated with anti UV coatings, anti fog coatings among other reasons.
What Hollywood knew that Leica users didn't was probably the use of good lens dedicated lens shades. Ever wondered why photographers don't use good effective lens shades so common in movie cameras? ;)

GPS
20-Mar-2011, 06:34
Some of the early glass types tarnish, others do not. I have an old Schneider Xenar Typ D which has natural tarnish that functions as a coating, but I have never seen an Aplanat with tarnish: It's the wrong type of glass for it.

I have a post-production-coated Rodenstock Eurynar as well as an original uncoated one of the same age. With eight air/glass surfaces, it makes a LOT of difference in flare and contrast.

Yes, it depends on the glass composition.

Dan Fromm
20-Mar-2011, 06:58
How do you know they don't have the natural tarnish?Inspection. The glasses are water white at all viewing angles.

Sometimes one has to look hard to see coating's effects. I have a couple of TTH and Wray lenses that are coated a nearly invisible light blue.

GPS
20-Mar-2011, 07:55
Inspection. The glasses are water white at all viewing angles.

...

Hmm. Sounds like a natural tarnish...:)

Dan Fromm
20-Mar-2011, 08:08
Hmm. Sounds like a natural tarnish...:)You can't see it either.

GPS
20-Mar-2011, 08:27
You can't see it either.

Exactly.
Or just in comparison to a new lens of the same kind - not exactly a practical way with old lenses...

Drew Wiley
20-Mar-2011, 09:38
Lens coating in the modern sense are an integral part of lens design. The characteristics of the lens can be fine-tuned not only by glass selection, but by how
these elements are coated. It is hard to imagine modern color photography without
such options, or many small camera lenses with multiple elements. There's a lot more to it than just flare control. But sometimes those old lenses have a look that
is prized and is hard to replicate with "improved" optics.

Nathan Potter
20-Mar-2011, 10:00
"Natural tarnish"? What exactly is that. Optical glass is about 90% SiO2 with varying constituents to pull the index. I suppose the SiO2 could pick up some additional native oxide/nitride on the surface which would differentiate it from the bulk material but that would be very thin, < say 200 angstroms, and not really visible from an interference point of view. Could there be an out diffusion of impurities from the bulk glass that would precipitate on the surface to a thickness approaching an interference film? Or is the tarnish just external contamination that is soft and could be wiped off? Are we just talking about dirt on old lens surfaces?

I can't say I have ever noticed this on old lenses but have heard comments about it in the past.

Nate Potter, Austin TX.

Two23
20-Mar-2011, 10:51
Thanks Dan et al. I knew that lens coating seemed to hit in a big way just after WW2, but didn't know for sure if Voigtlander etc. had ever coated their Heliars earlier than that. Apparently not. I am largely after a nostalgic look and love my Derogy Petzval. I'm even considering getting another lens, maybe even older. A pillbox meniscus lens or RR is under consideration. My thinking was that I could simply shoot at night with these and use my lighting system as the "shutter." This is proving to give very inconsistent results. What is happening is there is usually a fog or vapor in the air here, especially this time of year. That catches the light causing a flashball. Modern coated lenses seem to be able to handle that but uncoated lenses seem to lose most of their contrast from the flare. Many of my shots are made at night, and that seems to be challenging to an old lens. I am learning to predict what shots will be successful and which won't be though. I am going to try shooting with just the front two elements of the Derogy one of these nights soon. My thinking is that with half as many elements at work there should be less of a problem. I am learning a lot on this forum about things that just aren't mentioned on "regular" photo forums that are dedicated to the "hot camera of the day." Below is a shot I made with Derogy Petzval on HP5 and a shot made with D300 & modern Nikon 17-55mm f2.8.


Kent in SD

GPS
20-Mar-2011, 10:57
"Natural tarnish"? What exactly is that. Optical glass is about 90% SiO2 with varying constituents to pull the index. I suppose the SiO2 could pick up some additional native oxide/nitride on the surface which would differentiate it from the bulk material but that would be very thin, < say 200 angstroms, and not really visible from an interference point of view. Could there be an out diffusion of impurities from the bulk glass that would precipitate on the surface to a thickness approaching an interference film? Or is the tarnish just external contamination that is soft and could be wiped off? Are we just talking about dirt on old lens surfaces?

I can't say I have ever noticed this on old lenses but have heard comments about it in the past.

Nate Potter, Austin TX.

A natural tarnish on lens surface is a layer created on glass surface as it chemically reacts with the environment. Don't ask me what the chemistry is. The military guys noticed it on their binocs exposed to the harsh conditions (so goes the legend) in WWI (but it was known already in the 19th century). To their surprise new binocs did not show the same light transmission so they started to prefer their "worn" glass.
Germans later put their science boys to work on it and came to produce the first artificial lens coating. It was always amazing me that they classified the lens coating as a war secret. Could it be that they thought it was giving them such a military advantage in their tanks' binocs to see a little bit better? If that were so important one could always make binoculars with a wider aperture to get the same advantage. What is the additional weight in the 40+ tons tank anyway?
How do you see it on a lens? You don't - the sign of it is that the lens simply doesn't look "new" enough...:)

GPS
20-Mar-2011, 11:29
Thanks Dan et al. I knew that lens coating seemed to hit in a big way just after WW2, but didn't know for sure if Voigtlander etc. had ever coated their Heliars earlier than that. Apparently not.
...
Kent in SD

Kodak started to (soft) coat their lenses already before the WWII. Coated Heliars were in production during the WWII.

Arne Croell
20-Mar-2011, 11:32
"Natural tarnish"? What exactly is that. Optical glass is about 90% SiO2 with varying constituents to pull the index. I suppose the SiO2 could pick up some additional native oxide/nitride on the surface which would differentiate it from the bulk material but that would be very thin, < say 200 angstroms, and not really visible from an interference point of view. Could there be an out diffusion of impurities from the bulk glass that would precipitate on the surface to a thickness approaching an interference film? Or is the tarnish just external contamination that is soft and could be wiped off? Are we just talking about dirt on old lens surfaces?

I can't say I have ever noticed this on old lenses but have heard comments about it in the past.

Nate Potter, Austin TX.
In most cases, natural tarnish is a layer of SiO2 formed by leaching out the other glass constituents (PbO, CaO, BaO, P2O5, B2O3, Na2O, etc.) in the outer layer . This usually happens through reaction with moisture. Pure SiO2 has a pretty low index, so it can act as a coating for a high index base glass like a heavy flint (SF) type glass. Btw, 90% SiO2 is not true for many glasses - as an example, heavy flint types (SF) went up to 70% PbO. There are even some glasses without SiO2.

Drew Wiley
20-Mar-2011, 13:51
Many glass types including natural glass (obsidian) hydrate when exposed to air, and the resulting work of oxygen produces a hardened surface layer with minor optical properties of it own. This might be compounded by certain elements in the glass,
but tends to be a very slow yet steady process, though it can be accelerated by high
temperatures. When this surface layer get to be around 40 microns or so in thickness it tends to spall off. The moral of the story is, that if you've owned one
of these uncoated lenses with bloom for more than ten thousand years, you might want to post in on EBay before it loses most of its value.

Robbie Bedell
20-Mar-2011, 14:56
I have a 1903 Bausch and Lomb IIb tessar where I can really see the 'natural coating.' The glass has a reddish and greenish color on the surface. I have never shot any color film with it. I also have a 1914 CZJ 135 tessar with perfect glass and it's surface is just plain white as Dan describes. Perhaps it time it too will change...

http://robbiebedell.photoshelter.com

Struan Gray
20-Mar-2011, 15:23
A couple of thousand years in alkaline soil will do the trick nicely.

There are expired patents which hope to reproduce ancient glass patina as an anti-reflection coating. Boiling in alkali figured highly. The idea of an evaporated metal oxide is a direct line of deduction from there. I suspect the 'military secret' was as much to do with production engineering (how to make an efficient vacuum coating line) as with the raw science of 1/4-wave coatings.

Some of the early Contax coated lenses for the 35 mm rangefinders found it onto the civilian market in Sweden before the war. Some lucky amateurs got their hands on early colour film too. Whether you had to be a personal hunting buddy of Goering (who loved to holiday here), I don't know, but it's entirely possible.

Nathan Potter
20-Mar-2011, 15:57
Ah. Arne and Struan I should have surmised such. I'm aware that flat panel manufacturers sometimes use inexpensive soda lime glass coated with a thin deposited layer of SiO2, presumably to separate the applied circuitry from leachate from the glass. I also have PbO based wine glasses that devitrify (become cloudy at the surface) from dishwashing cycles. Also have some new wine glasses from Schott which are called Titanium Glass - I presume based on a titanium oxide formulation which is dishwasher proof and less breakable.

Of course I would have thought that optical glass would be of a more stabile composition, even historically, but I suppose that the impurities are needed to pull the index for improved design flexibility. I presume a small amount of rare earth additive to a boule can pull the index a fair bit due to the high atomic number - but being a large atom should be fairly stable in the glass matrix.

Well, I'm thinking out loud. All pretty interesting technology.

Nate Potter, Austin TX.

Bob Salomon
20-Mar-2011, 16:44
From Gepe:

Sometimes it appears that the glasses, mostly on older mounts, have a grey coating. Why is this and how can I clean the glass?

The grey coating you see on the glass is probably calcium-carbonate crystals emerging from a chemical reaction between the carbon-dioxide (CO2) in the air and the Calcium (Ca) in the glass. This can sometimes be seen as a grey haze on the surface of the glass.
It is a phenomenon that occurs with all glass materials, from the finest wineglasses on the shelf at home to normal windowpanes. After a period of time a grey surface appears which naturally has to be washed off to become clean again.
This problem is known among all glass manufacturers and they are, of course, trying to find a permanent solution to it, but so far they have only managed to delay the reaction.
It is difficult to determine how long a period of time it is before this greyish surface occurs, however, it is important to store the slide mounts in stable conditions, preferably dry and at a constant temperature. However, these crystals are not dangerous or harmful to the slide film, as it remains on the glass and does not transfer to the film.
A recommended method of cleaning glass slide mounts is to use a liquid lens cleaner and a smooth lens cleaning cloth.

Drew Wiley
20-Mar-2011, 16:58
Now we're entering a season where certain lens coatings are being liquid applied
rather than vacuum deposited. Struan's remark about attempt to burial coat glass
are interesting. I was just at a rockhound friend's house where he was showing me
his obsidian collection from all over the west. Sometimes I'd find examples myself
which looked almost as if they'd been multicoated. Pretty interesting subject, but
you'd probably have to have access to a mass spectrometer to understand what
really went on to produce all these colors.

lindy
20-Mar-2011, 18:28
Just as a side note Kodak was among the first to coat lenses (as early as 1939). they were supplying hard coated lenses to the military as early as 1942. I do believe that all of Kodak's professional Ektar lenses were coated.

GPS
21-Mar-2011, 02:38
Just as a side note Kodak was among the first to coat lenses (as early as 1939). ...

Make that 1938 to be more precise.

Lynn Jones
21-Mar-2011, 10:47
The first lens coating was accomplished in the US from l928 (B&J) 1930 (Kodak) others from 1931. The first published documents were in 1930 or so from UC by a PhD candidate for her dissertation. The first European artificial lens coating that I have actually seen was Germany in about 1937. It is possible that Zeiss was doing some of this in 1934 as you mention, but it sure must have been a secret.

Lynn

Lynn Jones
21-Mar-2011, 10:56
Sorry guys but my response was lost somehow. The first artificially coated lenses were done in the US in 1928/29 (B&J), 1930 by Kodak, several other manufacturers in the US in 1931 and later. All of the original coatings had a bluish cast except for the Kodak coatings which were were nearly invisible but with a slightly yellowish or golden cast. In fact, if I remember Kodak's advertising, they called it golden coating.

Thefirst published data was from a UC doctoral candidate's dissertation in about 1930 who supplied the data while being financially assisted by B&J.

The first coated lenses that I have acctually seen from Europe were German from 1937. So if as Dan says, Zeiss was doing some coating in 1934, it really must have been a secret and I can certainly appreciate that.

Lynn

Dan Fromm
21-Mar-2011, 12:08
Lynn, if US firms had reduced anti-reflection coating to practice in the early '30s, why didn't they commercialize the process? Where are the lenses? Where are advertisements touting the great advance? Inquiring minds want to know.

Two23
21-Mar-2011, 20:48
Lynn, if US firms had reduced anti-reflection coating to practice in the early '30s, why didn't they commercialize the process? Where are the lenses? Where are advertisements touting the great advance? Inquiring minds want to know.

Now the discussion is getting more interesting!


Kent in SD

GPS
22-Mar-2011, 03:38
Lynn, if US firms had reduced anti-reflection coating to practice in the early '30s, why didn't they commercialize the process? Where are the lenses? Where are advertisements touting the great advance? Inquiring minds want to know.

I think Lynn speaks about practical research done on lens coating... But Germans were doing their research too in the same time.

CCHarrison
22-Mar-2011, 04:15
A first hand source regarding coatings (October 1943)....

http://replay.waybackmachine.org/20060828145933/http://www.svc.org/H/WWII.pdf


Page 1, first paragraph reads:

"This whole business of non-reflective film apparently started the year I was born so I probably grew up with it although during most of that time, I didn’t know it. However I suppose it remained more or less a laboratory phenomenon until the first World War, when certain of the manufacturers whom I think may be present here today, experimented with means for improving the performance of optics by non-reflection coating. Fred Wright* also experimented with these coatings during that war. I think he was stationed with Bausch & Lomb at that time.

These films came to my attention about fifteen years ago [added -> about 1928] during a discussion of methods of improving optical performance. At that time many people reported that the use of films could really accomplish that end. A few years later, a good many people were working on it, among whom were the Messrs. Cartwright and Turner. Some of them may be here today."

*Dr. P. E. Wright, Technical Adviser Joint Optics Conm. ANMB.


Dan C.

Dan Fromm
22-Mar-2011, 05:19
Dan, thanks for the link. There's nothing in the document it points to about reduction to practice much (certainly not in 1928) before 1943. The idea was certainly out in the open but tools and techniques to implement it don't seem to have been.

Jim Galli
22-Mar-2011, 06:57
In the late 1960's, Burke and James, a large Chicago retailer, was having a love affair with all of the vintage lenses that virtually everyone else was casting aside as it were forever. B&J bought lots and lots of classic lenses and then coated them in their own shops? Or had someone who was doing it.

I've been buying these for the same reasons you mention although night photography isn't big on my list.

My most recent is a Cooke 15.5" Series IVb. I very nearly sent it back when it came as looking at it in the sunshine, it just didn't look good. But after using it and also re-inspecting I surmise that what I'm seeing is perfect glass polish but rather imperfect, even crude, coatings.

I have 14" B&L Tessar, 14" Cooke Aviar Air Ministry, 18" Cooke Portrait, the 15.5 mentioned above, and likely some others I haven't thought of. These were all classic designs that could only benefit from a coating service.

Other folks are shying away from these on Ebay. Typically B&J, bunk and junk to our friend Dan Fromm, would take an all brass beauty and paint it black with white inscriptions when they re-did them for re-sale, and they would put a small sticker on with their name on it. So from my user perspective, a double bargain, classic designs, coated, and the collectors want none of it.

E. von Hoegh
22-Mar-2011, 07:28
Dan, thanks for the link. There's nothing in the document it points to about reduction to practice much (certainly not in 1928) before 1943. The idea was certainly out in the open but tools and techniques to implement it don't seem to have been.

I have a pair of Spencer 7x50 Navy binoculars, which are coated throughout. They were made in '43, and had a sticker warning to clean them with care. The coating is almost gone from the eyepiece lenses, the rest are in good to excellent shape.

Katherine Blodgett at Schenectady G.E. did early research (1920s?) on antireflective coatings.

Struan Gray
22-Mar-2011, 08:14
Katherine Burr Blodgett is a name to conjure with. A pioneer woman scientist who actually received public and professional recognition. Her coatings were soft though :-)

http://www.flickr.com/photos/schenectady2009/3174208783/in/photostream/

I tried to dig out some original references, and quickly found that nationalism is alive and well in optics history, almost as if WWII was still being fought. The Germans credit Zeiss (1930s) and add Joseph Fraunhofer (1817) for etching lenses with acid to improve their transmission. The Brits give the nod to Dennis Taylor (1905) and Lord Rayleigh(1886). The Americans tend to favour Kodak, GE and other industrial concerns in the late 1930s and 40s. No doubt there is a forgotten Russian who invented it all long before that (first rule of literature searches: there is *always* a forgotten Russian who invented it all long before that). The patent literature for vacuum coating metal flourides onto glass really takes off in the early '40s.

This looks like an interesting article, but it's behind a paywall for most, including me right now: http://iopscience.iop.org/1464-4258/1/S/305. The Wikipedia article on camera lenses has more references than the one on anti-reflection coatings.

These days, it's all nanotech and metamaterial coatings. Amid the hype, it's worth noting that Lord Rayleigh was well aware that nanometer-scale layers would have a significant effect. Blodgett's films were probably the first really controllable way of making the right structures.

Emmanuel BIGLER
22-Mar-2011, 09:18
I'm coming late to this discussion but since we are digging into historical references
I think the name of Olexander (Alexander ?) Smakula should be mentioned for his works at Carl Zeiss in 1934-35. (http://en.wikipedia.org/wiki/Olexander_Smakula)

It is very intereresting to learn that an academic work on coatings occured in the US as early as 1930. If the results were publicly disclosed, no patent could have been issued in the US exactly on the same basis as described in the academic work, but not all results have to be actually disclosed when an academic work is performed in cooperation with a private company. However many patents of course could be issued on specific techniques and applications of coatings even after this academic work was published.

Another historical note (may be it was mentioned before ? sorry for re-posting) is that all German patents issued during the nazi regime were cancelled by allied forces after WW-II.
Hence Schneider Kreuznach could start bringing to the market coated lenses right after WW-II ! This would have been more difficult due to the Zeiss patent...
And another consequence of cancelling German patents in 1945 is that, of course, allied forces could dig into the German patent data-base without limit, but this was also granted to ... German and Japanese companies !!

Two23
22-Mar-2011, 19:02
Another historical note (may be it was mentioned before ? sorry for re-posting) is that all German patents issued during the nazi regime were cancelled by allied forces after WW-II.
Hence Schneider Kreuznach could start bringing to the market coated lenses right after WW-II ! This would have been more difficult due to the Zeiss patent...
And another consequence of cancelling German patents in 1945 is that, of course, allied forces could dig into the German patent data-base without limit, but this was also granted to ... German and Japanese companies !!

Wow! That sorts of explains everything, doesn't it! I wondered why there seemed to be very very few references to actual commercial coated lenses before WW2, but there seemed to be an explosion of them just after. The forum here is like a little history class, LOL!


Kent in SD

Dan Fromm
23-Mar-2011, 03:05
Kent, if you read the document for which Dan C. posted a link, you'll see that development of relatively inexpensive relatively mass-produced reliable vacuum pumps is what made commercial coating possible. Patents and secrecy, another way of spelling trade secrets, had little to do with it.

Nathan Potter
23-Mar-2011, 09:52
I think Fromm is right here. The explosion of technical R&D in the US and Europe after WWII led to the rapid development and availability of vacuum deposition equipment, then quickly to setups using such equipment for mass production. Simultaneously advancements in precise thickness control of thin films meant that hard coatings could be applied at reasonable cost and with the required great precision. Soon lenses with AR coatings became a marketing mantra and coatings were required by all manufacturers in order to stay competitive.

The capability to experiment and demonstrate a coating process certainly existed in the 20s and 30s using early but somewhat crude vacuum technology as exemplified by the interesting K. Blodgett note.

Nate Potter, Austin TX.

E. von Hoegh
23-Mar-2011, 10:29
Kent, if you read the document for which Dan C. posted a link, you'll see that development of relatively inexpensive relatively mass-produced reliable vacuum pumps is what made commercial coating possible. Patents and secrecy, another way of spelling trade secrets, had little to do with it.

I wonder. Commercial large - ish scale production of vacuum tubes started in 1920, becoming a truly large production in a couple years. Maybe the pumps used were too big, too expensive to be used for AR coating?

Cor
24-Mar-2011, 07:11
This looks like an interesting article, but it's behind a paywall for most, including me right now: http://iopscience.iop.org/1464-4258/1/S/305. The Wikipedia article on camera lenses has more references than the one on anti-reflection coatings.

These days, it's all nanotech and metamaterial coatings. Amid the hype, it's worth noting that Lord Rayleigh was well aware that nanometer-scale layers would have a significant effect. Blodgett's films were probably the first really controllable way of making the right structures.

I could get hold of above article, I guess posting it is not ok, but a PM to me with your private Email address shouldn't hurt, should it?

I just got a pre-war 16.5 cm Angulon according to the Schneider site born in 1937, which has a distinct blue coating, does not look like a tarnish yellow, so I have to assume it was coated later. It does stand up against pretty harsh light unlike the uncoated Wolly WA II 159mm which is flare sensitive even under a high cast sky..

Best,

Cor

Bob Salomon
24-Mar-2011, 07:24
Let's not forget that in the day smoking in the studio and darkroom was quite a common practice. In fact, the ash from a cigarette would be used to intensify an area on a print in some darkrooms. All that smoke did sometimes form a coating on lenses.

Struan Gray
24-Mar-2011, 07:47
I could get hold of above article, I guess posting it is not ok, but a PM to me with your private Email address shouldn't hurt, should it?

Thanks for the offer Cor. I have an institutional subscription to the IOP journals, but when I wrote my post I was away from my usual desk and couldn't access the file. I have it now.

I too am leery of broadcasting copyright material, even given my profound dislike of the academic journal system. But odd copies won't matter much - not least because in Sweden at least we have open public access to university libraries, so anyone can get a copy of the article by using a terminal at their nearest institution.

The article is an interesting read, and has all the relevant historical references, as well as a useful history of C20th industrial coating.


Struan

Two23
24-Mar-2011, 10:00
I just got a pre-war 16.5 cm Angulon according to the Schneider site born in 1937, which has a distinct blue coating, does not look like a tarnish yellow, so I have to assume it was coated later. It does stand up against pretty harsh light unlike the uncoated Wolly WA II 159mm which is flare sensitive even under a high cast sky..


I have an older SA 90mm f5.6 that is definitely and deliberately monocoated. It too has a blueish-purple coating. I detect only one coating when I do the light test. How can I find the age if I have the serial number?


Kent in SD

Mark Sampson
24-Mar-2011, 10:41
look at Schneider's website- they have lots of data about their older lenses. They began to multi-coat their lenses in the mid-late '70s; and they put 'multicoated' on the nameplate, so there's no confusion.

GPS
24-Mar-2011, 11:28
...

... It does stand up against pretty harsh light unlike the uncoated Wolly WA II 159mm which is flare sensitive even under a high cast sky..

Best,

Cor

Not if you use a correctly made lens shade.
It is said somewhere that when Kodak was doing their coating research they found that inner baffles between lens elements are sometimes of a greater effect than the coating itself. They redesigned some of their lenses because of it.

Cor
24-Mar-2011, 11:32
Not if you use a correctly made lens shade.
It is said somewhere that when Kodak was doing their coating research they found that inner baffles between lens elements are sometimes of a greater effect than the coating itself. They redesigned some of their lenses because of it.


You are right, I learned that the hard way, I forgot my compendium, I'll be more careful next time, also some images shot with an older single coated 300mm Symmar showed signs of flare, even with the sun behind me and using the darkslide above the lens, the snow and water bounced light around..

Best,

Cor

E. von Hoegh
24-Mar-2011, 11:33
That Wollensak, if the f9.5 version has 8 air-glass surfaces, 6 of them internal. No lens shade will tame it. The 165 Angulon has 4 surfaces, 2 of them internal.

Cor
24-Mar-2011, 11:34
I have an older SA 90mm f5.6 that is definitely and deliberately monocoated. It too has a blueish-purple coating. I detect only one coating when I do the light test. How can I find the age if I have the serial number?


Kent in SD
You can find it here (http://www.schneideroptics.com/info/age_of_lenses/)..

Best,

Cor

GPS
24-Mar-2011, 11:41
That Wollensak, if the f9.5 version has 8 air-glass surfaces, 6 of them internal. No lens shade will tame it. ...

Of course it will. All the light that goes on the surface of an external lens element has an effect on the lens optical output. Regardless of the number of air-glass passages. To limit the light input to the useful light only (as much as possible) always effects the lens optical output - regardless of the number of air-glass passages.

E. von Hoegh
24-Mar-2011, 11:48
Of course it will. All the light that goes on the surface of an external lens element has an effect on the lens optical output. Regardless of the number of air-glass passages. To limit the light input to the useful light only (as much as possible) always effects the lens optical output - regardless of the the air-glass passages.

I'm well aware of that. I used the lens on 8 x 10, with a properly adjusted compendium. Still flare, and sometimes quite a bit of it.
A nice lens otherwise; I'd grab up a coated version if I could.

Have you ever used the lens in question?

GPS
24-Mar-2011, 12:00
That Wollensak, if the f9.5 version has 8 air-glass surfaces, 6 of them internal. No lens shade will tame it. ...


Of course it will. All the light that goes on the surface of an external lens element has an effect on the lens optical output. Regardless of the number of air-glass passages. To limit the light input to the useful light only (as much as possible) always effects the lens optical output - regardless of the number of air-glass passages.


I'm well aware of that. ...
Have you ever used the lens in question?

Well, if you're well aware of that why do you then suggest the opposite?
A compendium is just an approximate lens hood, far from being a fully efficient one.
You don't need to use all lenses in order to know that a proper lens shade will help all of them - it's just a question of the optical geometry laws..

Cor
25-Mar-2011, 01:04
..altijd het laatste woord, vermoeiende man...