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Thread: Apertures for Zeiss Triple Convertible

  1. #11
    Edison's Avatar
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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by j.e.simmons View Post
    Isn’t the aperture change the reason you use the single element behind the aperture.
    OP, B&L licensed the Protar from Zeiss so for the Protar V and Vii, the lenses are the same. For the most part Series IV lenses were very different. I believe yours is a Series VII.
    You can find lots of old manuals at
    https://www.cameraeccentric.com/

    He has some problems that might cause your browser to show a warning, but just ignore the warning.

    BTW, all of the Protar I’ve received have had the lower focal length on the front and the longer on the back. All of the Zeiss and B&L manuals above have the longer listed as the front lens. In use, I haven’t seen any difference.
    Yes that’s where I found the pdf. I read on a thread here the reason to use the single lens behind is that the aperture somewhat corrects for some aberration that is normally corrected for when both lenses are used.

    Thanks for the confirmation on b and l. Mine came to me with the longer at the front too.

  2. #12
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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by David Lindquist View Post
    j.e. simmons has beat me to it to some extent. If you look at the early 20th century B&L catalogues on the camera eccentric website you'll see Bausch & Lomb's equivalents to your two lenses had focal lengths of 8 3/4 and 11 3/16 inches respectively. Combined they made a 5 5/8 inch focal length objective.

    Circa 1910 Carl Zeiss Jena changed the labeling of their lens focal lengths from millimeters to centimeters. The 224 mm lens became a 22 cm lens and the 285 mm lens became a 29 cm lens; in combination they made up a 14.5 cm lens.

    David
    Cool. So this is a pre 1910 lens. I read the first year the Korona ii was made was 1909 so maybe it’s an early one. Thanks!

  3. #13
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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by j.e.simmons View Post
    You can find lots of old manuals at
    https://www.cameraeccentric.com/

    He has some problems that might cause your browser to show a warning, but just ignore the warning.

    BTW, all of the Protar I’ve received have had the lower focal length on the front and the longer on the back. All of the Zeiss and B&L manuals above have the longer listed as the front lens. In use, I haven’t seen any difference.
    Reading the b and l manual.

    It says the aperture is f/7 in combination. So 143mm/7=20mm. My max aperture is 25mm so I’m not sure why the difference.

    But it says f7 for the combo of #2 and #3, with f/12.5 being their independent max apertures. I was picturing the the 285 to have a higher f stop than the 224.

    It also says when using just a rear lens, the front is replaced by a “screen ring”. I wonder if that is actually needed and if so how do I get one. It just occurred to me it means a clear filter.

    Mine also has the spiral focusing mount, so I suppose that’s for fine focus.

    Thanks again. I’ll keep digging.

    Edit: I understand more now. Series vii is the thread size. I’m looking for an adapter like this maybe. https://www.ebay.com/itm/26579396112...mis&media=COPY

  4. #14

    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by Dugan View Post
    Custom Bellows does top-notch work.
    Apparent aperture is the measured size as viewed from the front, whether there's a front element in place or not.
    I very much agree regarding the high quality work and good service by Custom Bellows, UK.

  5. #15
    Edison's Avatar
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    Re: Apertures for Zeiss Triple Convertible

    I see now. The housing does go to 25mm but it’s ineffective for a bit because the lens is limited to 20mm.

    Edit: so I know the fl is 143mm and max aperture is f7. 143mm/7=20.4mm aperture.

    I also know with the 224mm, the max aperture is 12.5. 224mm/12.5=18mm max aperture. So the apparent aperture is 2.5mm smaller. This is about 90% so hopefully it’s linear and I can use this conversion.

    For example (224mm/6mm)(.9)=f/33.6.

  6. #16

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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by Edison View Post

    Edit: I understand more now. Series vii is the thread size. I’m looking for an adapter like this maybe. https://www.ebay.com/itm/26579396112...mis&media=COPY
    You are referring to the "VII" on each lens bezel, right?

    This has nothing to do with series VII filters. What you have is a pair of Series VII Protars. The Series VII was Dr. Paul Rudolph's final version of of the Protar (typically labeled on the bezel "Protarlinse"). It consisted of four glass elements cemented together, you can see the configuration in the appropriate Zeiss catalogs on the camera eccentric website. When two Series VII Protars are paired up in a shutter or barrel, probably the more common way they were used, Zeiss referred to the combination as a Series VIIa objective, also their literature would refer to this combination as a "Double Protar." The single component, the Series VII had a maximum aperture of f/12.5.
    The "Series VIIa" or "Double Protar" was "faster" than either of its components. A symmetrical combination (both cells the same focal length) is the "fastest". My circa 1933 Zeiss catalog shows two 29 cm Protars combined to give a 17 cm f/6.3 objective; a 29 + 22 cm combination gave a 14.5 cm f/7 objective and 29 + 18 cm yielded a 13 cm f/7.7 objective.

    Each Series VII Protar had its own serial number. Based on four samples in my records, when the combination was symmetrical the serial numbers were consecutive; e.g. two 59 cm cells, serial numbers 918934 and 918935. When the two cells are of different focal lengths the serial numbers of course will not be consecutive.

    Based on several samples and dating them according to Hartmut Thiele's Fabrikationsbuch Photooptik II Carl Zeiss Jena it looks like Zeiss stopped including the "VII" on the bezels of these Protars about 1929-1930. I think the wide angle f/18 Protar continued to be marked with a "V". Don't know offhand what Bausch & Lomb's practice was.

    This is probably more than anyone wanted to know...

    David
    Last edited by David Lindquist; 28-Jul-2022 at 11:46.

  7. #17

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    Re: Apertures for Zeiss Triple Convertible

    And furthermore Alan...
    I successfully scanned a print-out of a table from a Zeiss publication (which I've not subsequently been able to find anywhere on the internet) which I got from an eBay listing in 2008. It shows the diameters of stops in millimeters for both the single Protar components and the "Double-Protars" (plus the f/18 Protars). It's in English and a lot easier to use, I think, then that "round-about" thing. The resulting pdf is reasonably legible. It is from the later era when the focal lengths were in centimeters. If you want to PM me your email address I'll be happy to send this. Anyone else is welcome and if someone could post it here, that might be useful too.

    Interestingly it looks like the diameter of the stops for the single components can be simply calculated from the focal length in millimeters. For the Double-Protar a factor is given which I think is to account for that entrance pupil thingy.

    David

  8. #18
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    Re: Apertures for Zeiss Triple Convertible

    When using the single elements of my Zeiss Series VII set, I use a filter on the front of the shutter to ensure no dust gets inside the shutter. S.K. Grimes made the adapter for me. For black & white film I usually use a yellow filter, but I want to experiment with using an orange filter to see how well that increases the negative's contrast. Not recommending doing that--I just want to experiment.

    A point of clarification: I actually had Grimes make filter adapters for both the front and rear of the shutter. This has allowed me to experiment with a wide range of combinations of close-up filters for soft-focus effects. Still experimenting.

    Keith

  9. #19
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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by David Lindquist View Post
    You are referring to the "VII" on each lens bezel, right?

    This is probably more than anyone wanted to know...

    David
    No, I want it all.

  10. #20

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    Re: Apertures for Zeiss Triple Convertible

    Quote Originally Posted by Edison View Post
    It also says when using just a rear lens, the front is replaced by a “screen ring”. I wonder if that is actually needed and if so how do I get one. It just occurred to me it means a clear filter.
    Yes a 'screen' means a filter. But in this case, the filter is not a clear but a yellow one; it improves single cell sharpness a lot, reducing the influence of the lens chromatic aberration.

    The original Zeiss filter of the era was not plane yellow but somewhat on the amber side so it wasn't a sharp-cut filter and thus introduced less flare as part of the stray light reflecting inside the filter glass was absorbed - the same way it is absorbed in film antihalation layers. Also, the glass that filter was made of was not fluorescing under blue and UV radiation like all the modern yellow to red filter glass types do. Probably that glass was more expensive; it is not manufactured anymore. Modern non-fluorescing filters include Wrattens and Tiffens (which are actually Wrattens cemented between two pieces of clear glass) and all the yellow-green glass ones. The yellow-greens are also not of the sharp-cut type so they introduce minimal flare.

    Quote Originally Posted by Keith Fleming View Post
    For black & white film I usually use a yellow filter, but I want to experiment with using an orange filter to see how well that increases the negative's contrast.
    The contrast with both yellow and orange filters will be exactly the same (and MUCH lower than without any filter). Those filters improve sharpness, not the contrast. And as the main influence on the chromatic aberration is in the blue, violet and especially in the UV regions (and Protars are quite transparent in the near UV), the sharpness difference with a yellow and an orange filter will be too tiny to be seen in actual photos. A yellow-green filter will also give very similar sharpness but about twice less flare (= more contrast) than the yellow, orange and red ones.

    .... But I wonder why anybody needs filter adapters for these lenses. My Protar cells have the common 40.5x0.5mm threads, and any 40.5mm filter fits in the barrel in the place of the front cell. Are shutter-mounted Protar cells mechanically different?

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