Leitz glass transforms uv in to visible light

[Mustafa Umut Sarac]

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I have found Leitz glass should transform the ultraviolet light in to visible light. This is true all the glasses since 1930s up to 90s. I dont classify later lenses as leitz lenses , each one lacks one particular specification and I did not like any of them. Ultraviolet transformation is the first huge success of the thoriated lenses and they are the most sensitive. UV gives wet plate photographs to catch the smallest creases on the dress and textile and add huge swaths of smooth tones and lots of shadows and sharp details Thats true for leitz lenses when they record face or body muscles least.

 

Dont miss the paper I will add to next post. Due to size limit , I cant put to the this post .

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[Mustafa Umut Sarac]

YOU SHOULD READ THAT PDF to understand why leica is leica and why you gave tons of money.

wet plate comparison.pdf

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[frame-it]

how many Leica lenses actually had thorium?

this obviously doesn't apply to vintage Leitz lenses on digital Leica bodies, only to film images.

[Mustafa Umut Sarac]

15 minutes ago, frame-it said:

how many Leica lenses actually had thorium?

this obviously doesn't apply to vintage Leitz lenses on digital Leica bodies, only to film images.

I cant answer your question how many lenses had thorium but thorium lenses made to transform the uv to visible strongest. I have 1938 Elmar , I had 1942 Summitar and I had 1946 Elmar and in few years with better glasses , they made huge leap. I used 1954 hektor and 1960s summicron and they made great lenses with colors pop , details pop and the tonal grades were longer. I asked to schott several times about the availability of new glasses with uv to visible transformation capability but they did not returned. I will call them tomorrow. I dont think digital or film make a difference. Its the visible light where uv been converted.

[pgk]

3 hours ago, Mustafa Umut Sarac said:

I have found Leitz glass should transform the ultraviolet light in to visible light.

Glass does NOT transform wavelegths of light. UV will record on sensors or films which are sensitve to it. I do not understand what the intention of your post or the assocated pdf article are. They show nothing which has not been understood for a very long time.

The 35mm Summicron M v.4 is a very poor transmitter of UV. I know because I had one repaired and this required recementing which needed a heavy dose of UV to cure due to its poor transmission.

Edited November 20 by pgk

[Anbaric]

https://www.youtube.com/watch?v=0xD9qEdHFIE&t=25s

Edited November 20 by Anbaric

[Anbaric]

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1 hour ago, Mustafa Umut Sarac said:

I cant answer your question how many lenses had thorium but thorium lenses made to transform the uv to visible strongest. I have 1938 Elmar , I had 1942 Summitar and I had 1946 Elmar and in few years with better glasses , they made huge leap. I used 1954 hektor and 1960s summicron and they made great lenses with colors pop , details pop and the tonal grades were longer. I asked to schott several times about the availability of new glasses with uv to visible transformation capability but they did not returned. I will call them tomorrow. I dont think digital or film make a difference. Its the visible light where uv been converted.

None of these lenses contained thoriated glass, only the earliest collapsible Summicrons (and their 'Summitar*' prototypes) did.

[willeica]

2 hours ago, Mustafa Umut Sarac said:

YOU SHOULD READ THAT PDF to understand why leica is leica and why you gave tons of money.

wet plate comparison.pdf 2.35 MB · 10 downloads

Thanks for this, but the wet plate image here shows a far greater range of tones than either the colour or B+W ( looks like a poor conversion) images. This has nothing to do with the lenses used and I fail to see any connection to Leitz or Leica. What is most important here are the materials used. Wet plates would typically have the photographer's own concoction and film and sensor types can vary considerably and film and sensor types would vary considerably. I recently looked at this in the context of dry plates used in a surviving late 19th Century Darkroom and found that UV (varying with time of day, latitude etc) could have considerable effect on dry plates from that era. Generally most photographers in that era learnt how to work with this.  

As regards lenses, yes, modern lenses with multi-coating and different formulae would produce what might be considered 'superior' images. The different types of glass might make some difference. For what it's worth, I noticed that a new hob which I bought recently for my kitchen had Schott glass! However, the single biggest difference which has been made with lenses since the time of Barnack was the introduction of coating from the 1940s onwards.

My friend Roland Zwiers, who posts on this forum, has examined the early types of film used with Leica cameras. He is of the view that Barnack used yellow filters on early cameras (pre-Leica 35mm cameras such as the Ur-Leica) as he would have been using film that was not panchromatic. However, there is no period or visual evidence that Barnack used such filters. He and I recently examined boxes of negatives taken by Barnack between 1914 and 1918 at the Leica Archive. While the negatives showed some variation as regards tones and details, it was not really possible to tell if a yellow filter and been used in any particular case. There are other factors as well, such as the exposure at the time of taking and then the processing in the darkroom.

Thorium lenses can end up over time being effectively yellow coated https://en.wikipedia.org/wiki/File:Yellowing_of_thorium_lenses.jpg#:~:text=If stored in the dark,to a UV light source. and this might contribute to a yellow filter effect when used with Black and white film, but there are too many variables in all of this to make any definitive conclusions. Other manufacturers used the same materials as Leitz and I am not sure that there is anything in Leitz lenses to distinguish them from other superior lenses of the same period e.g. Zeiss or Schneider .

I would be interested to hear how you consider the document you attached has any relevance to he superiority or otherwise of Leitz lenses. I agree with everything that my friend Paul (pgk) has written.

 

William

 

[pgk]

May I add that very early glass (of which there were few types - flint and crown) seems to show poor transmission of some colour and the result can be almost 'blocky' saturated colours if used for colour photography today. This too will substantially change the tonal results with some emulsions. This was not dealt with in the pdf. In the ~1890s newer glass started to improve things and by the 1920s and 1930s better glass and more sensitive panchromatic films (as evidenced from the movies) meant that B&W was vastly better tonally than it had been. As willeica said, lens coating was the next major step forward. I am not sure when UV filters were first used but would guess this was when sensitivity of emulsions started to rise significantly. If anyone knows it would be interesting to compare the dates when UV filters were introduced and film sensitivity increases.

Edited November 20 by pgk

[Anbaric]

Some substances used in various types of glass can cause it to fluoresce at visible wavelengths when illuminated by UV light. But significant fluorescence is unlikely to be a desirable property of the optical glass used to make lenses - it would probably just reduce contrast (which might, e.g., be an issue for critical applications like microscopy):

https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/10/ti-36_fluorescence_of_optical_glass_us.pdf

In any case, I don't think this has anything to do with the improved performance of Leica lenses over time, which is due to improved designs (computer aided from quite early on - Leitz worked with Zuse from the 1950s), improved glass with desirable properties in the visible range (like a particular refractive index) and, as William mentions, coating (later multicoating).

[dpitt]

2 hours ago, pgk said:

Glass does NOT transform wavelegths of light. UV will record on sensors or films which are sensitve to it. I do not understand what the intention of your post or the assocated pdf article are. They show nothing which has not been understood for a very long time.

The 35mm Summicron M v.4 is a very poor transmitter of UV. I know because I had one repaired and this required recementing which needed a heavy dose of UV to cure due to its poor transmission.

Maybe a dumb question for @willeica and @Anbaric :
Could it be that it is actually the other way around?

Older glass probably had a more limited bandwidth for UV wavelengths than the current glass. This would maybe make older lenses act as if they have a built in UV filter, and any filter close enough to visible light will affect the visible wavelengths also, thus resulting in visible tonal changes.

Edited November 20 by dpitt

[Mustafa Umut Sarac]

@Anbaric @willeica William , our friend gave an excellent paper and nailed the answer. This is why leica is leica but % 95 of the leica users never awakens to this quality. I think you should have a summitar , try portraits at night time with filament electric light illuminated place , more the bulb , more the quality. Dont use digital camera , use kodak cinema film. Your subject should show her face muscles streched. Bulbs should be 4 meters far. 

Let me give you a secret , put your summitar or 1950s ektar lens close to your eye and look to your wife at portrait distance at night. If you cant see the quality , you have no business with leica.

 

[pgk]

49 minutes ago, dpitt said:

Could it be that it is actually the other way around?

Older glass probably had a more limited bandwidth for UV wavelengths than the current glass. This would maybe make older lenses act as if they have a built in UV filter, and any filter close enough to visible light will affect the visible wavelengths also, thus resulting in visible tonal changes.

No. UV filters came about because of the over bluish colouration, especially at altitude, due to UV being imaged as violet/blue on film which was sensitive to UV wavelengths.. The UV filter (and very light pink 'skylight' filters) were intended to counteract this and persist to this day although they are now essentially for protection rather than anything else because sensors have their own built in filter as a cover glass to prevent UV/IR contamination or don't as Leica discovered with the IR sensitivity of the M8. There are specialists who will remove and replace the sensor cover glass to adjust spectral sensitivity to specified UV wavelengths.(Loads of info here: https://www.ultravioletphotography.com/content/)

Edited November 20 by pgk

[250swb]

5 minutes ago, Mustafa Umut Sarac said:

@Anbaric @willeica William , our friend gave an excellent paper and nailed the answer. This is why leica is leica but % 95 of the leica users never awakens to this quality. I think you should have a summitar , try portraits at night time with filament electric light illuminated place , more the bulb , more the quality. Dont use digital camera , use kodak cinema film. Your subject should show her face muscles streched. Bulbs should be 4 meters far. 

 

This is a very narrow and slightly absurd claim. I’m a landscape photographer, and I use true vintage lenses and more modern Leica lenses (1930s) with many film stocks, so what will I see with Kodak Cine film at night with a filament bulb? I’m guessing nothing? Or is there an actual practical example you can post of how this theory works in everyday photography?

[Anbaric]

3 minutes ago, Mustafa Umut Sarac said:

Let me give you a secret , put your summitar or 1950s ektar lens close to your eye and look to your wife at portrait distance at night. If you cant see the quality , you have no business with leica.

One thing I would avoid doing is holding thoriated glass close to your eye - some Ektars contain a substantial amount of thorium, and your cornea is vulnerable to radiation.

[willeica]

1 hour ago, dpitt said:

Maybe a dumb question for @willeica and @Anbaric :
Could it be that it is actually the other way around?

Older glass probably had a more limited bandwidth for UV wavelengths than the current glass. This would maybe make older lenses act as if they have a built in UV filter, and any filter close enough to visible light will affect the visible wavelengths also, thus resulting in visible tonal changes.

I suspect that the photographic medium being used probably had a greater impact than the lens in years gone by.  See below extract from this which is about modern dry plates which seek to replicate late 19th Century processes.  https://www.pictoriographica.com/technicals-and-tips.html . Even as late as the 1950s there were many different film /plate ratings and reliability of the rating of different stocks was not assured. Also in the 1980s every time I bought a new lens I always bought a UV or Skylight filter to go with it, something I find to be unnecessary today. I have highlighted the most relevant parts below. While this relates to dry plates, the same issues arose in the early years of 35mm photography. Barnack used a film tester called M875 to test the 35mm film stock for his cine camera. I held M875 in my hands a few weeks ago and also Barnack's handwritten notebook where he wrote about how he used the film tester. 

 

METERING OUTDOORS - VARIATIONS IN EFFECTIVE SPEED

If you dig through enough literature from the dry plate era, you will eventually come across references to exposure tables, which provided compensating factors to adjust for correct exposure over the course of the year and time of day.  It wasn't until well into the 20th Century that the effective speed became independent from the amount of UV available...either by advances in dye sensitization or adding UV filtering dyes to the overcoating layer of the emulsion.

So to obtain a properly exposed plate, you will want to compensate for time of year / time of day just like they did in the 19th Century. 

In practice, J. Lane Dry Plates meter at approximately ASA 2.  The plates see primarily in the UV, so this metering is dependent on the available UV levels.  In general the UV levels can vary significantly over the course of the year, so the effective speed that you meter at should be adjusted.  The ASA 2 rating was established under clear northerly lighting in March at my latitude (42 North), so in summer you will achieve a faster effective speed and in winter you must expose at a slower effective speed.   

Pictured below is a seasonal and hourly ASA rating table, based on data from an H&D 1880's era Actinograph.  This gives an indication of what ASA value you should set your meter to based on time of year and time of day at 51.5 degrees North (or South).  

 

Meter primarily off of your main subject of interest.  On a perfectly exposed dry plate photograph, the sky will be overexposed and vegetation will look dark.  This is again due to the way the world looks in the UV and blue as "seen" by the plates.  When you meter for your shot, be aware of how much of the sky or vegetation your meter is registering and compensate accordingly.  Plan to overexpose a clear sky by about 2 stops... an overcast sky by about 1 stop.

This is based on my practical experience with the type of photography that I do.  I use the Light Meter app on my smartphone, which is sort of a spot meter and works well for my needs.  Keep in mind the color response of the emulsion, and which colors will be rendered brighter and darker. 

You can also try placing a blue filter in front of your meter, which will more closely mimic the response of the emulsion.

METERING INDOORS

Changes in effective speed under artificial lighting is an effect that even modern film experiences today.  During the dry plate era, artificial lighting had an even more pronounced effect. 

 

William 

Edited November 20 by willeica

[Anbaric]

Even modern UV filters vary quite a lot in their transparency to UV wavelengths. In this test, various Hoyas filter out pretty much everything below about 380 nm, whereas a Tiffen is still transmitting half the UV at around 330 nm. Lenses are of course much more complex, and fans of UV photography spend a lot of time figuring out which lenses let through enough UV to be useful. With this much variability, I suspect it would be difficult to make any general claim about how lenses from different eras behaved.

[pgk]

3 minutes ago, Anbaric said:

I suspect it would be difficult to make any general claim about how lenses from different eras behaved.

It would be interesting to find out. I expect that information about the spectral absorption of optical glass is available today but older glass may be more difficult. I would be interested to find out though. I may try photographic a Colour Check Chart with a variety of different age lenses at some point when I have time.

[Mustafa Umut Sarac]

44 minutes ago, Anbaric said:

Even modern UV filters vary quite a lot in their transparency to UV wavelengths. In this test, various Hoyas filter out pretty much everything below about 380 nm, whereas a Tiffen is still transmitting half the UV at around 330 nm. Lenses are of course much more complex, and fans of UV photography spend a lot of time figuring out which lenses let through enough UV to be useful. With this much variability, I suspect it would be difficult to make any general claim about how lenses from different eras behaved.

look to the photographs , use good lenses like summitar , it will teach you where to look.

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[willeica]

20 minutes ago, Anbaric said:

Even modern UV filters vary quite a lot in their transparency to UV wavelengths. In this test, various Hoyas filter out pretty much everything below about 380 nm, whereas a Tiffen is still transmitting half the UV at around 330 nm. Lenses are of course much more complex, and fans of UV photography spend a lot of time figuring out which lenses let through enough UV to be useful. With this much variability, I suspect it would be difficult to make any general claim about how lenses from different eras behaved.

I agree with your last point. I have not seen tables for particular modern lenses with compensation for UV. There were also filter factors around at one time, but I have not seen them recently for UV filters. We are, of course, spoilt today with automatic TTL exposure and the ability to adjust everything with post processing software. The graphs I have posted above have compensating factors built in for different times of the day and year and different locations ( this one is for London) to take account of factors such as UV, which indicates just how difficult things were.  There were also compensations back then for focal length.

I have gone through the notebooks of a photographer which were filled out between 1890 and 1920. He simplified things for himself by always using f16 and varying the exposure time and he also always took his images between 12 and 3 pm in the day (orange or blue on the table above) while noting the nature of the available light. He used exposure tables, although I also found what looks like part of an early Watkins Actinograph in his darkroom   He also had compensating factors for his various lenses which were based upon focal length and effective aperture. He wrote these into his notebook sometime after 1888. At that time there was no standard aperture system and he actually scratched what we would recognise as the 'modern' aperture scale onto his Dallmeyer Rapid Rectilinear lens which had an earlier aperture system. The table below indicates the range of aperture systems back then. The RPS set the manufacturers on the road to standardising apertures but this only took effect after 1895

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The table above is from the late 19th Century, but the following table of speed ratings for films/plates dates from as late as 1952. Some of the tables written into film boxes about sea, sunny, hazy etc conditions may take UV into account, but tests would be needed to confirm this for each historical film/plate brand. 

 

Making comparisons between eras is almost impossible given the extent of the variations which applied, but the amazing thing is that photographers managed to great pictures right through this time. The white skies of the 1850s soon gave way to detailed skies as the sensitivity to blue got ramped up, but even they have a period charm.

Where all of this takes us with Leitz lenses is unclear. The Leitz lenses were good, but were probably no better than the best contemporary lenses from competitors. There are apocryphal stories about the World War II period when it was said that the German military favoured Zeiss lenses for their Leicas. My friend Bill Rosauer (derleicaman around these parts)has a story about the birth of the Summarex lens and how Leitz had to work hard to try to get the military to accept it. Maybe if he reads this he can contribute the story.

Finally, Leitz only shifted from the continental aperture system to the 'international scale' in the 1940s. 

There is a lot more to this, but I will leave it at that.

William