British v German rangefinders

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dunmunro
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Re: British v German rangefinders

Postby dunmunro » Sat Sep 12, 2015 5:40 pm

Christian VII. wrote:
dunmunro wrote:Both the UK (Barr and Stroud) and USA ( Baush and Lomb) introduced coated optics in the late 1930s.


They were apparently not the same as the anti reflective coatings by Zeiss which were a closely guarded secret until the end of the war as far as I have read.

It's true that the use of lens coatings wasn't new (IIRC the Allies called it blooming), but the anti reflective coatings invented by Smakula at Zeiss in 1935 was a game changer. It provided an increase in the light transmitting properties of each lens of ~80%, which was a lot more than any previous lens coating.


The paper to read on this topic is:

The early days of optical coatings from the Journal of Optics A:
The primary driver in World War II was the improvement
of the light transmission of optical instruments, such as
binocular telescopes, especially for use at sea. Although
the coatings were considered highly secret, all major parties
involved in the war were occupied in much the same way.
The efforts at Barr and Stroud in Glasgow are described by
Moss and Russell [18]. The company actually began work
on antireflection coatings just before the war, and by 1941
the improvement of around 60% in light transmission had
induced the Admiralty to order that all submarine periscopes
should be coated. Binoculars too gained enormously
from antireflection coatings that permitted their effective
use in conditions much darker than ever before. It was
calculated that coated binoculars permitted an additional
30–45 min of clear seeing at dusk and dawn [19]. While
this was happening in Britain, Geffcken was busy creating
multilayer antireflection coatings in Germany [17], and
Francis Turner, with two patents on magnesium fluoride
antireflection coatings gained with Cartwright at MIT, was
joining the Bausch and Lomb Company in the United States


There are numerous other sources to show that the UK and USA were producing antireflective coatings on all surfaces of selected military optics from the late 1930s. Optical first surface coatings were being applied in the UK prior to WW1.

The key improvement was applying the coatings to all optical surfaces and that occurred nearly simultaneously in the UK, USA and Germany.

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Re: British v German rangefinders

Postby dunmunro » Sat Sep 12, 2015 7:52 pm

The difference between all coated and all uncoated optics is much greater than between all coated and improved (multicoated) all coated optics.


The table
also illustrates the significance of antireflection
coatings in maximising
transmission and image contrast.

EYEPIECE TYPE REFLECTION LOSSES
Uncoated / Magnesium Fluoride / Multi-coating
SINGLE LENS 8% / 2% / 0.2% (two surface)
ORTHOSCOPIC 16.8% / 4.8% / 0.8% (four surface)
ULTRA-WIDE ANGLE 41.44% / 11.4% / 2.4% (ten surface)


from:
EVOLUTION of the ASTRONOMICAL EYEPIECE

Christian VII.
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Re: British v German rangefinders

Postby Christian VII. » Sat Sep 12, 2015 8:27 pm

Yeah I read it, but again there was apparently a great difference in the effectiveness of the coatings and how they were applied, esp. when combined with special made lenses. Also far from as many Allied optical devices were applied with anti reflective coatings as were German devices.

The Germans deposited CaF2 & MgF2 anti reflective coatings on their lenses as well using a method to achieve a stronger & better coating. The result was an increase in light transmission of over 80% pr. lens, and since most optical devices used five or more lenses this quickly added up. Coatings were deposited in either one, two or even three layers by Zeiss in 1938.

The Germans were well ahead in lens manufacture as well, being the only ones to add Lanthanum to their lenses to drastically improve clarity for example, as well as using plasma cleaning of lenses.

In the end this resulted in a marked advantage in the clarity & brightness of image in German optics, something which allowed them to make bigger and better optical equipment. This can also be witnessed by reading allied troop accounts where the amazement of German optical equipment was very pronounced, esp. in terms of binoculars and telescopic sights.

Finally if we look at the range finders on the German, British & US capital ships there also seems to be a marked difference in the availability of magnifications and FoV, with the German RF'ers providing steps in magnification up to 50x in comparison to the 25x of the US & British RF'ers for example. This was most likely only possible due to the use of more lenses with better clarity and light gatherning qualities.
Last edited by Christian VII. on Sat Sep 12, 2015 9:09 pm, edited 2 times in total.

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Re: British v German rangefinders

Postby dunmunro » Sat Sep 12, 2015 9:04 pm

Christian VII. wrote:Yeah I read it, but again there was apparently a great difference in the effectiveness of the coatings and how they were applied, esp. when combined with special made lenses. Also far from as many Allied optical devices were applied with anti reflective coatings as were German devices.

The Germans deposited CaF2 & MgF2 anti reflective coatings on their lenses as well using a method to achieve a stronger & better coating. The result was an increase in light transmission of over 80% pr. lens, and since most optical devices used five or more lenses this quickly added up. Coatings were deposited in either one, two or even three layers by Zeiss in 1938.

The Germans were well ahead in lens manufacture as well, being the only ones to add Lanthanum to their lenses to drastically improve clarity for example, as well as using plasma cleaning of lenses.

In the end this resulted in a marked advantage in the clarity & brightness of image in German optics, something which allowed them to make bigger and better optical equipment. This can also be witnessed by reading allied troop accounts where the amazement of German optical equipment was very pronounced, esp. in terms of binoculars and telescopic sights.

Finally if we look at the range finders on the German, British & US capital ships there also seems to be a marked difference in the availability of magnifications and FoV, with the German RF'ers providing steps in magnification up to 50x in comparison to the 25x of the US & British RF'ers for example. This was most likely only possible due to the use of more lenses with better clarity and light gatherning qualities.


The table that I posted at 0952PM shows the effect of coating optics, and the effect per lens is shown.

The difference in performance between a lens with basic single surface coatings and one with the best possible modern coatings is almost undetectable except when measured carefully with test equipment.

The US NDRC tested a German 4M RF side by side with the equivalent US 3.5M unit and found the German unit to be overall very similar but slightly inferior, while similar testing showed little difference betwen US and UK RFs,

by 1939, there was no way to "drastically" improve military optics because the performance needed for combat effectiveness was much less than that needed for high quality photography or astronomy, for example. Side by side testing of Allied and German optics didn't show any huge advantage for German optics, which is no surprise, because the basic physics of light and optics place limits on ultimate performance.

Christian VII.
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Re: British v German rangefinders

Postby Christian VII. » Sat Sep 12, 2015 9:11 pm

dunmunro wrote:
Christian VII. wrote:Yeah I read it, but again there was apparently a great difference in the effectiveness of the coatings and how they were applied, esp. when combined with special made lenses. Also far from as many Allied optical devices were applied with anti reflective coatings as were German devices.

The Germans deposited CaF2 & MgF2 anti reflective coatings on their lenses as well using a method to achieve a stronger & better coating. The result was an increase in light transmission of over 80% pr. lens, and since most optical devices used five or more lenses this quickly added up. Coatings were deposited in either one, two or even three layers by Zeiss in 1938.

The Germans were well ahead in lens manufacture as well, being the only ones to add Lanthanum to their lenses to drastically improve clarity for example, as well as using plasma cleaning of lenses.

In the end this resulted in a marked advantage in the clarity & brightness of image in German optics, something which allowed them to make bigger and better optical equipment. This can also be witnessed by reading allied troop accounts where the amazement of German optical equipment was very pronounced, esp. in terms of binoculars and telescopic sights.

Finally if we look at the range finders on the German, British & US capital ships there also seems to be a marked difference in the availability of magnifications and FoV, with the German RF'ers providing steps in magnification up to 50x in comparison to the 25x of the US & British RF'ers for example. This was most likely only possible due to the use of more lenses with better clarity and light gatherning qualities.


The table that I posted at 0952PM shows the effect of coating optics, and the effect per lens is shown.

The difference in performance between a lens with basic single surface coatings and one with the best possible modern coatings is almost undetectable except when measured carefully with test equipment.

The US NDRC tested a German 4M RF side by side with the equivalent US 3.5M unit and found the German unit to be overall very similar but slightly inferior, while similar testing showed little difference betwen US and UK RFs,

by 1939, there was no way to "drastically" improve military optics because the performance needed for combat effectiveness was much less than that needed for high quality photography or astronomy, for example. Side by side testing of Allied and German optics didn't show any huge advantage for German optics, which is no surprise, because the basic physics of light and optics place limits on ultimate performance.


The effects are not identical though, some coatings and layering techniques work better than others.

The German AR coatings for example provided an improvement pr. lens of over 80%, where'as the best Allied coatings achieved 60%. But the Allies didn't coat their military optics to anywhere near the same extend as the Germans, infact most of the Allied optical equipment such as binoculars & telescopes weren't coated at all.

But also as mentioned coatings wasn't the only thing, the Germans were also well ahead in the manufacture of the lenses themselves, adding Lanthanum to their lenses to drastically improve clarity and making use of plasma lens cleaning.

The below are a few quotes from a report to the Allied supreme commander (Roosevelt) in March 1945:

"Our sight reticule is okay, but our sights are not nearly powerful enough.
These new telescopic sights are an improvement over the old periscope sight,
but are still not powerful enough. The Germans seem to have better glass in theirs."

- Coulter M. Montgomery, 1st Lt. 66th AR

"I took from a German officer a pair of field glasses 10 x 50, the best glasses I have ever seen. On two occasions, I was able to pick up an anti tank position and a mortar position at a range of about one mile, when these same two targets could not be seen using a pair of GI glasses, 7 x 50"
- Sgt. George A. Barden, 2nd AD Scout Section, 1945.

"The German sight is far better than anything we are using today. It takes a bright light in order to se them - and we do not have that. The same thing goes for our field glasses; if we could spot them, we could fire on them ourselves, or get artillery to fire on that spot. I know that we have the facilities to build better optical equipment - why don't we?"
-Donald Morgan, T/4, 67th AR.

"The German telescopic sights mounted in their tanks are far superior to ours. In particular, it is more powerful. Infact all their optical equipment is superior to ours"
- Sgt. Lewis A Taylor, US Army 2nd AD, 1945

"The matter of tank gun sights has caused us much concern. I have looked through and worked with sights in German Mark V and Mark VI tanks as well as our own. I find that the German sight has more magnifying power and clearness that our own, which is a big advantage to a gunner"
- Lt. Colonel Wilson M. Hawkins, US Army 3rd Bn 67th AR, 1944

The magnification of the German sight is greater than ours, on the Mark V & Mark VI, and has an adjustable reticle for the type of ammunition being fired. The lens seems to be made of better glass than ours. They also seem to have better light transmission capabilities."
- Phillip C. Calhoun, Major, 3rd Battalion, 66th AR

In other words the German reputation for making superior optics didn't just arrive from out of thin air :)
Last edited by Christian VII. on Sat Sep 12, 2015 9:31 pm, edited 1 time in total.

dunmunro
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Re: British v German rangefinders

Postby dunmunro » Sat Sep 12, 2015 9:22 pm

Christian VII. wrote:

The effects are not identical though, some coatings and layering techniques work better than others.

The German AR coatings provided an improvement pr. lens of over 80%.

The below are a few quotes from a report to the Allied supreme commander (Roosevelt) in March 1945:

"Our sight reticule is okay, but our sights are not nearly powerful enough.
These new telescopic sights are an improvement over the old periscope sight,
but are still not powerful enough. The Germans seem to have better glass in theirs."

- Coulter M. Montgomery, 1st Lt. 66th AR

"I took from a German officer a pair of field glasses 10 x 50, the best glasses I have ever seen. On two occasions, I was able to pick up an anti tank position and a mortar position at a range of about one mile, when these same two targets could not be seen using a pair of GI glasses, 7 x 50"
- Sgt. George A. Barden, 2nd AD Scout Section, 1945.

"The German telescopic sights mounted in their tanks are far superior to ours. In particular, it is more powerful. Infact all their optical equipment is superior to ours"
- Sgt. Lewis A Taylor, US Army 2nd AD, 1945

"The matter of tank gun sights has caused us much concern. I have looked through and worked with sights in German Mark V and Mark VI tanks as well as our own. I find that the German sight has more magnifying power and clearness that our own, which is a big advantage to a gunner"
- Lt. Colonel Wilson M. Hawkins, US Army 3rd Bn 67th AR, 1944

The magnification of the German sight is greater than ours, on the Mark V & Mark VI, and has an adjustable reticle for the type of ammunition being fired. The lens seems to be made of better glass than ours. They also seem to have better light transmission capabilities."
- Phillip C. Calhoun, Major, 3rd Battalion, 66th AR


Your statement:
"The German AR coatings provided an improvement pr. lens of over 80%." is not true as the table I posted above shows.

Posting anecdotal statements is meaningless and is not a measure of the state of the art of Allied versus German optics. The Allies almost always preferred mass produced, lower cost, equipment for most applications, precisely because it could be built cheaply in large numbers. However, for cutting edge applications, such as key naval optics, there was little difference between Allied and German optics.

Christian VII.
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Re: British v German rangefinders

Postby Christian VII. » Sat Sep 12, 2015 9:44 pm

dunmunro wrote:
Christian VII. wrote:

The effects are not identical though, some coatings and layering techniques work better than others.

The German AR coatings provided an improvement pr. lens of over 80%.

The below are a few quotes from a report to the Allied supreme commander (Roosevelt) in March 1945:

"Our sight reticule is okay, but our sights are not nearly powerful enough.
These new telescopic sights are an improvement over the old periscope sight,
but are still not powerful enough. The Germans seem to have better glass in theirs."

- Coulter M. Montgomery, 1st Lt. 66th AR

"I took from a German officer a pair of field glasses 10 x 50, the best glasses I have ever seen. On two occasions, I was able to pick up an anti tank position and a mortar position at a range of about one mile, when these same two targets could not be seen using a pair of GI glasses, 7 x 50"
- Sgt. George A. Barden, 2nd AD Scout Section, 1945.

"The German telescopic sights mounted in their tanks are far superior to ours. In particular, it is more powerful. Infact all their optical equipment is superior to ours"
- Sgt. Lewis A Taylor, US Army 2nd AD, 1945

"The matter of tank gun sights has caused us much concern. I have looked through and worked with sights in German Mark V and Mark VI tanks as well as our own. I find that the German sight has more magnifying power and clearness that our own, which is a big advantage to a gunner"
- Lt. Colonel Wilson M. Hawkins, US Army 3rd Bn 67th AR, 1944

The magnification of the German sight is greater than ours, on the Mark V & Mark VI, and has an adjustable reticle for the type of ammunition being fired. The lens seems to be made of better glass than ours. They also seem to have better light transmission capabilities."
- Phillip C. Calhoun, Major, 3rd Battalion, 66th AR


Your statement:
"The German AR coatings provided an improvement pr. lens of over 80%." is not true as the table I posted above shows.

Posting anecdotal statements is meaningless and is not a measure of the state of the art of Allied versus German optics. The Allies almost always preferred mass produced, lower cost, equipment for most applications, precisely because it could be built cheaply in large numbers. However, for cutting edge applications, such as key naval optics, there was little difference between Allied and German optics.


Your table doesn't disprove it dunmunro, it just shows one combination, that you must understand.

Alexander Smakula's coatings achieved an improvement of over 80% as well as harder and more durable coatings.

"Prior to 1935 all refractive lenses were made with no protective or anti-reflection treatments; the bare glass was exposed to the air or cemented to other lens components. So a notable amount of the light (4 to 6 percent per surface) approaching a lens was reflected off each lens surface - front AND back too. Consider an easy example for a moment - what do you see when you walk by a window pane? Your reflection! There is enough light reflected off that glass surface so that you can discern the image. The same thing was happening in telescopes, eyepieces, camera lenses - but worse since optical instruments and lenses consist of multiple elements of glass, there was the tendency not only to reflect light off the first lens surface but also to reflect light back and forth between uncoated air-spaced elements in the system. This not only decreased overall light throughput, but often resulted in 'ghost' or secondary images showing up on film or to the eye; an astronomer might be seeing a star in the field that was not really there. So it was another noteworthy milestone when on November 1, 1935 a team led by Dr. Alexander Smakula (b. 9 Sep. 1900, d. 17 May 1983), a staff member at Carl Zeiss AG at Jena, patented the first anti-reflective (T Transparenz) coatings thereby improving light transmission dramatically over uncoated lenses in binoculars to over 80 per cent, reducing ghost images and finding other applications for the advances of optics in many other fields. The AR coatings remained a closely guarded technology, a military secret, applied only to the most critical optical elements until about 1940. After then they were applied to the lens elements of more and more devices (binoculars, rangefinders, etc.). By the mid 1940's the consumer might have had their first introduction to this technology with their prescription eyeglasses.

By 1990 Zeiss Oberkochen would improve the anti reflective coatings to transmit more than 90 percent of the light entering a binocular (the T* designation). In 1988 "Phase Correction" coatings were introduced on all Carl Zeiss Oberkochen roof prism binoculars. Phase Correction facilitates a more uniform throughput of light across a wide portion of the visual spectrum thereby resulting in further improvements of resolution and contrast of systems incorporating roof prisms."


http://www.company7.com/zeiss/history.html
http://www.zeiss.com/sports-optics/en_d ... dards.html
http://www.rifleshootermag.com/shooting ... ugh_glass/

In 1994 Zeiss achieved a 91% improvement pr. lens, and their newest coatings today can achieve a 99% improvement.

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Re: British v German rangefinders

Postby dunmunro » Sun Sep 13, 2015 7:01 am

I don't think you understand basic optical principles.

https://mhcocm.wordpress.com/2011/12/28 ... -coatings/

You don't have to look very hard to discover that antireflective coatings were in use prior to 1935.

and Zeiss has no monopoly on this technology, before or after WW2.

http://www.bdimitrov.de/kmp/technology/SMC.html

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Re: British v German rangefinders

Postby alecsandros » Mon Sep 14, 2015 7:46 am

dunmunro wrote: However, for cutting edge applications, such as key naval optics, there was little difference between Allied and German optics.

... "of the same type".

But German capital ships tended to have somewhat more powerfull equipment then contemporary comparable ships.
A German 10.5m rangefinder could be , probably, close to a British 10.5m rangefinder in terms of accuracy. But Bismarck mounted 10.5m rangefinders, while Prince of Wales mounted 9 meter rangefinders.

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Re: British v German rangefinders

Postby dunmunro » Mon Sep 14, 2015 9:32 am

alecsandros wrote:
dunmunro wrote: However, for cutting edge applications, such as key naval optics, there was little difference between Allied and German optics.

... "of the same type".

But German capital ships tended to have somewhat more powerfull equipment then contemporary comparable ships.
A German 10.5m rangefinder could be , probably, close to a British 10.5m rangefinder in terms of accuracy. But Bismarck mounted 10.5m rangefinders, while Prince of Wales mounted 9 meter rangefinders.


PoW carried 2 duplex 15ft (4.6m) RFs in her two 14in DCTs, and 4 x 15ft RFs in her 4 x HADTs. She also carried 2 x 41ft (12.5m) duplex RFs in A and Y turret and and a 30ft (9m) duplex RF in B turret. A duplex RF is equivalent to two RFs built into one housing.

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Re: British v German rangefinders

Postby alecsandros » Mon Sep 14, 2015 9:40 am

dunmunro wrote:
alecsandros wrote:
dunmunro wrote: However, for cutting edge applications, such as key naval optics, there was little difference between Allied and German optics.

... "of the same type".

But German capital ships tended to have somewhat more powerfull equipment then contemporary comparable ships.
A German 10.5m rangefinder could be , probably, close to a British 10.5m rangefinder in terms of accuracy. But Bismarck mounted 10.5m rangefinders, while Prince of Wales mounted 9 meter rangefinders.


PoW carried 2 duplex 15ft (4.6m) RFs in her two 14in DCTs, and 4 x 15ft RFs in her 4 x HADTs. She also carried 2 x 41ft (12.5m) duplex RFs in A and Y turret and and a 30ft (9m) duplex RF in B turret. A duplex RF is equivalent to two RFs built into one housing.

I did not know about the 12.5m baselength RFs !

However, we should note that the main rangefinders were those which served the control towers, and those were of considerably smaller baselength.

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Re: British v German rangefinders

Postby Christian VII. » Tue Sep 15, 2015 9:58 am

dunmunro wrote:I don't think you understand basic optical principles.

https://mhcocm.wordpress.com/2011/12/28 ... -coatings/

You don't have to look very hard to discover that antireflective coatings were in use prior to 1935.

and Zeiss has no monopoly on this technology, before or after WW2.

http://www.bdimitrov.de/kmp/technology/SMC.html


I do understand the basics dunmunro, but I don't think you do when you keep overlooking that there were difference types of coating materials and techniques. Your links only prove what I've been saying all along :)

As already proven light transmissions can be improved by well over 90% with the use of AR coatings, and in WW2 the Germans were the only ones to apply hard coatings capable of delivering an improvement of over 80% (not to mention being the only ones to use Lathanum in their lense making as well as plasma cleaning) The best allied coatings were not only softer (less durable) but they also provided at most a 60% improvement, and finally were only applied to a few select pieces of equipment, like Uboat periscopes. Meanwhile the Germans made mass use of their hard T coatings in almost all their optical equipment and all the way down to perscription glasses.

I think this also explains why the Germans generally fielded larger and more complex optical equipment incoperating more lenses, as their coatings and lenses allowed them to do so without sacrificing anything in clarity, brightness or FoV.

In 1972 Zeiss introduced the T* coatings which improved light transmission by 91%, and in 1994 they introduced a new coating capable of 95%. Today we are reaching almost a complete double in improvement at 99.5%.

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Re: British v German rangefinders

Postby dunmunro » Tue Sep 15, 2015 9:05 pm

Christian VII. wrote:
dunmunro wrote:I don't think you understand basic optical principles.

https://mhcocm.wordpress.com/2011/12/28 ... -coatings/

You don't have to look very hard to discover that antireflective coatings were in use prior to 1935.

and Zeiss has no monopoly on this technology, before or after WW2.

http://www.bdimitrov.de/kmp/technology/SMC.html


I do understand the basics dunmunro, but I don't think you do when you keep overlooking that there were difference types of coating materials and techniques. Your links only prove what I've been saying all along :)

As already proven light transmissions can be improved by well over 90% with the use of AR coatings, and in WW2 the Germans were the only ones to apply hard coatings capable of delivering an improvement of over 80% (not to mention being the only ones to use Lathanum in their lense making as well as plasma cleaning) The best allied coatings were not only softer (less durable) but they also provided at most a 60% improvement, and finally were only applied to a few select pieces of equipment, like Uboat periscopes. Meanwhile the Germans made mass use of their hard T coatings in almost all their optical equipment and all the way down to perscription glasses.

I think this also explains why the Germans generally fielded larger and more complex optical equipment incoperating more lenses, as their coatings and lenses allowed them to do so without sacrificing anything in clarity, brightness or FoV.

In 1972 Zeiss introduced the T* coatings which improved light transmission by 91%, and in 1994 they introduced a new coating capable of 95%. Today we are reaching almost a complete double in improvement at 99.5%.


Most German military optics were uncoated, as were most Allied Optics. This information is widely available, and all you have to do is look for it:

"Although some Zeiss Kriegsmarine 6X30’s did have coated optics, the German Army Dienstglas did not."
https://www.flickr.com/photos/binocwpg/7516684888

"1943 10 x 50 Dientsglass...
The BLC dientsglas uncoated model was produced in large quantities."
http://www.binoculars-cinecollectors.co ... 9_10x.html



Maximum light transmission was 100% (obviously!!!)

EYEPIECE TYPE REFLECTION LOSSES
Uncoated / Magnesium Fluoride / Multi-coating
SINGLE LENS 8% / 2% / 0.2% (two surface) = 92 /98 /99.8 % transmission
ORTHOSCOPIC 16.8% / 4.8% / 0.8% (four surface) = 83.2 / 95.2 /99.2 % transmission
ULTRA-WIDE ANGLE 41.44% / 11.4% / 2.4% (ten surface) 58.56 / 88.6 / 97.6% transmission

The difference in performance between coated and multicoated is negligible in actual use. The difference in performance between coated (except for external surfaces) and fully coated is negligible. The difference in performance between coated and uncoated is not very great for simple optics such as a tank gunners telescope, and it's only with very complex optics with many optical surfaces where coatings will convey much of an advantage, but all you have to do is take a modern pair of multicoated binoculars out at night , to know that even with modern coatings that they are still not very efficient when used with a Mk1 eyeball.

This website discusses WW2 binoculars and gives info regarding the advantages of coatings, but also how clever optical design can minimize light loss even with uncoated optics.

The IJN was considered the master of naval warfare at night and their optics were almost all uncoated...

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Re: British v German rangefinders

Postby dunmunro » Tue Sep 15, 2015 9:08 pm

Christian VII. wrote:
dunmunro wrote:I don't think you understand basic optical principles.

https://mhcocm.wordpress.com/2011/12/28 ... -coatings/

You don't have to look very hard to discover that antireflective coatings were in use prior to 1935.

and Zeiss has no monopoly on this technology, before or after WW2.

http://www.bdimitrov.de/kmp/technology/SMC.html


I do understand the basics dunmunro, but I don't think you do when you keep overlooking that there were difference types of coating materials and techniques. Your links only prove what I've been saying all along :)

As already proven light transmissions can be improved by well over 90% with the use of AR coatings, and in WW2 the Germans were the only ones to apply hard coatings capable of delivering an improvement of over 80% (not to mention being the only ones to use Lathanum in their lense making as well as plasma cleaning) The best allied coatings were not only softer (less durable) but they also provided at most a 60% improvement, and finally were only applied to a few select pieces of equipment, like Uboat periscopes. Meanwhile the Germans made mass use of their hard T coatings in almost all their optical equipment and all the way down to perscription glasses.

I think this also explains why the Germans generally fielded larger and more complex optical equipment incoperating more lenses, as their coatings and lenses allowed them to do so without sacrificing anything in clarity, brightness or FoV.

In 1972 Zeiss introduced the T* coatings which improved light transmission by 91%, and in 1994 they introduced a new coating capable of 95%. Today we are reaching almost a complete double in improvement at 99.5%.


Most German military optics were uncoated, as were most Allied Optics. This information is widely available, and all you have to do is look for it:

"Although some Zeiss Kriegsmarine 6X30’s did have coated optics, the German Army Dienstglas did not."
https://www.flickr.com/photos/binocwpg/7516684888

"1943 10 x 50 Dientsglass...
The BLC dientsglas uncoated model was produced in large quantities."
http://www.binoculars-cinecollectors.co ... 9_10x.html



Maximum light transmission was 100% (obviously!!!)

EYEPIECE TYPE REFLECTION LOSSES
Uncoated / Magnesium Fluoride / Multi-coating
SINGLE LENS 8% / 2% / 0.2% (two surface) = 92 /98 /99.8 % transmission
ORTHOSCOPIC 16.8% / 4.8% / 0.8% (four surface) = 83.2 / 95.2 /99.2 % transmission
ULTRA-WIDE ANGLE 41.44% / 11.4% / 2.4% (ten surface) 58.56 / 88.6 / 97.6% transmission

The difference in performance between coated and multicoated is negligible in actual use. The difference in performance between coated (except for external surfaces) and fully coated is negligible. The difference in performance between coated and uncoated is not very great for simple optics such as a tank gunners telescope, and it's only with very complex optics with many optical surfaces where coatings will convey much of an advantage, but all you have to do is take a modern pair of multicoated binoculars out at night , to know that even with modern coatings that they are still not very efficient when used with a Mk1 eyeball.

This website discusses WW2 binoculars and gives info regarding the advantages of coatings, but also how clever optical design can minimize light loss even with uncoated optics.

The IJN was considered to be a master of naval warfare at night and their optics were probably all uncoated...

dunmunro
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Re: British v German rangefinders

Postby dunmunro » Wed Sep 16, 2015 3:55 am

My previous post got messed up.

This website discusses WW2 binoculars and gives info regarding the advantages of coatings, but also how clever optical design can minimize light loss even with uncoated optics.


http://www.brayebrookobservatory.org/Br ... OCOLL.html

Seeger, Military Binoculars and Telescopes in Army, Air Force and Marine:
"[page 331] In 1935/36, Alexander Smakula (Zeiss, Jena) developed the
lens coating, a reflection reducing coating for optical elements. For
all optics, especially thoise with numerous surfaces, the coating (also
called 'blue coating') is a valuable means to increase the transparency
and therefore the brightness of the image. In the marine optics, the
coating was especially useful. U-boat periscope optics were the first
to receive this new coating, along with the Navy field glasses. In
Germany, Navy optics and tank aiming field glasses were the only items
manufactured with coated optics; and other German military models
usually didn't have coating
(and when it is there, that nearly always
means it was applied later, and the original condition is falsified.)

For military optics from the U.S., Great Britain or Canada, the
sequence is similar to the one in Germany: Marine optics were the first
to receive the blue coat, but only during the course of the war. In
chart 2, we can see that in the U.S. in 1944, coating of military optics
was quite common. At least 5 of the listed models are coated, and since
one model is 'not coated', it is therefore more of an exception than the
rule."


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