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Thread: "When did pre-war Zeiss start applying coatings?" and other questions about Tessars

  1. #11
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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    Quote Originally Posted by senderoaburrido View Post
    Very informative Bernice. Thanks to all for the warnings about manufacturers coating old lenses as a service.

    I need for the lens to be uncoated so as to increase the amount of UV light passing through.

    I've been shooting wet plate for three years now, and honestly haven't seen much if any difference between using coated lenses and uncoated. I am using sunlight as my light source, not a UV light. Since I haven't tried it I don't know if that makes any difference. Below photo used the Velostigmat 12 inch on tin type. Outdoor shade photo.


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  2. #12
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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    A 240cm Tessar would be 2400mm and the largest Tessar I know was the 1200mm f15...
    The 240mm 1:9 Zeiss Jena Tessar is likely the APO Tessar and was made post WWII and was coated even though it was marked in cm and not mm.
    Apparently there was a batch of 24cm f9 Jena Tessars made in 1929 but these would be far rarer than the post war lenses.

  3. #13

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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    As it happens Zeiss did not make a 24 cm/ 240 mm Tessar. Based on Hartmut Thiele's Fabrikationsbuch Photooptik II Carl Zeiss Jena the Tessar between 21 cm and 30 cm in focal length was 25 cm/ 250 mm. The Apo-Tessar did come in a focal length of 24 cm/ 240 mm. If that difference is important to you, the Schneider Xenar, which follows the Tessar formula, was made with a 24 cm focal length. A pre-World War II version would be uncoated (with the caveats already mentioned.)

    David

  4. #14

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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    Topic of UV transmission of lenses has been discussed previously on this topic:
    https://www.largeformatphotography.i...ustar-37/page4

    Reply# 37, UV transmission chart of various lenses.

    Reply# 38, UV transmission graphs of Schneider lenses. Schneider graph for the 360mm Tele Xenar is for their last multicoated version according to Robert Kipling apps engineer at Schneider USA in the 90's. Note the APO artar which is a dialyte formula has about 80% transmission at 400nm. Rapid attenuation past 420nm of the APO Symmar (modern Plasmat) was specifically designed in for good color rendition using color films from that era. Color films were affected by UV light, to address this problem, view camera lens providers re-designed their offerings to attenuate uv to aid in color reproduction.

    Lens coatings alone are not the primary factor to lens UV transmission, optical glass types figures into this. Schneider Xenar (circa 1967), Tele Xenar, D-Claron and Dagor type g-Claron appears to have the most UV transmission to 365nm.

    Zeiss made a 105mm UV Sonnar for Hasselblad long ago with a transmission range of 215 to 700nm (quartz and fluorite elements used).
    https://www.zeiss.com/content/dam/co...r-43105-en.pdf

    This was a curiosity published some years ago on wet plate portraits and strobe power needed using modern light modifiers.
    https://petapixel.com/2015/12/11/sho...udio-lighting/

    12,000 watt seconds of strobe power seems lots today, back in the days of sheet film color transparency commercial AD images, 12,000 watt seconds of strobe power was very common. Bit surprised that strobe flash tubes with UV output specific to wet plate sensitivity needs.


    Bernice



    Quote Originally Posted by senderoaburrido View Post
    I need for the lens to be uncoated so as to increase the amount of UV light passing through. I chose Tessars specifically because they appear to be the best compromise between general acuity of the image while possessing very few elements and less total glass from front-to-back than many other common designs. I've also read that even the oldest copies tend to produce relatively sharp images, which is in my interest, as I intend to shoot portraits in the UV.

  5. #15

    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    Quote Originally Posted by Bernice Loui View Post
    Topic of UV transmission of lenses has been discussed previously on this topic:
    https://www.largeformatphotography.i...ustar-37/page4

    Reply# 37, UV transmission chart of various lenses.

    Reply# 38, UV transmission graphs of Schneider lenses. Schneider graph for the 360mm Tele Xenar is for their last multicoated version according to Robert Kipling apps engineer at Schneider USA in the 90's. Note the APO artar which is a dialyte formula has about 80% transmission at 400nm. Rapid attenuation past 420nm of the APO Symmar (modern Plasmat) was specifically designed in for good color rendition using color films from that era. Color films were affected by UV light, to address this problem, view camera lens providers re-designed their offerings to attenuate uv to aid in color reproduction.

    Lens coatings alone are not the primary factor to lens UV transmission, optical glass types figures into this. Schneider Xenar (circa 1967), Tele Xenar, D-Claron and Dagor type g-Claron appears to have the most UV transmission to 365nm.

    Zeiss made a 105mm UV Sonnar for Hasselblad long ago with a transmission range of 215 to 700nm (quartz and fluorite elements used).
    https://www.zeiss.com/content/dam/co...r-43105-en.pdf

    This was a curiosity published some years ago on wet plate portraits and strobe power needed using modern light modifiers.
    https://petapixel.com/2015/12/11/sho...udio-lighting/

    12,000 watt seconds of strobe power seems lots today, back in the days of sheet film color transparency commercial AD images, 12,000 watt seconds of strobe power was very common. Bit surprised that strobe flash tubes with UV output specific to wet plate sensitivity needs.


    Bernice
    Incredibly helpful! Thanks Bernice. It seems many of the older Clarons are perfectly suited. I would be happy to use one of those instead of these old Tessars, given that all the examples I can find seem to possess threaded front barrels to accommodate the necessary lens filters.

  6. #16

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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    Think Schneider Claron lens cells thread direct into industry standard shutters like Copal. Check the lens barrel -vs- shutter spacing and threading before attempting this.
    What remains will be the aperture scale for the re-fitted lens.

    Schneider did offer Claron series lenses in shutter, they are GOOD. They are typically full aperture of f9 or smaller for longer focal lengths.


    Bernice

    Quote Originally Posted by senderoaburrido View Post
    Incredibly helpful! Thanks Bernice. It seems many of the older Clarons are perfectly suited. I would be happy to use one of those instead of these old Tessars, given that all the examples I can find seem to possess threaded front barrels to accommodate the necessary lens filters.

  7. #17

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    Re: "When did pre-war Zeiss start applying coatings?" and other questions about Tessa

    IMO, it shouldn't be necessary to worry about coating on lenses for this application. For a relatively simple anti-reflection coating, when used out of its normal spectral range, it will have degraded AR performance (so it will be like having no coating), but it won't be extra good at absorbing light. The effects are likely to be a few percent, not tens of percent. Many coating specialists don't give plots of reflection blueward of 400 nm, but here's a useful plot from Edmund Optics: https://www.edmundoptics.com/knowled...tion-coatings/

    Here, I highlighted the important curve to look at with a couple of arrows (click to enlarge). The mauve line is the reflectance of a MgF2 coating optimized for 550nm, which is pretty much what a "single coated" lens is likely coated with. It has a minimum reflectance of maybe 1.2% at 550nm. At say 370 nm, which is well outside its design range, the reflectance has increased to 3%, which is still less than the ~4% reflectance of uncoated glass. Transmission = 1-reflectance, and for a lens with a small number of optical surfaces, you wouldn't notice much transmission difference - the main effect of the coating is to reduce scattered light and flare.

    Click image for larger version. 

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