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Thread: Caltar II-N 210mm f5.6 aperture scale help

  1. #1

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    Caltar II-N 210mm f5.6 aperture scale help

    Iíve picked up a 210mm f5.6 Caltar II-N from ye old auction site. It was banged up enough to be cheap but is in functionally perfect condition... with one issue. The Copal No. 1 shutter itís mounted in has an aperture scale for an f6.8 lens.
    Iíd like to make a correct aperture scale. I know that I could do it myself with some time and effort, but I also know that this is an incredibly common lens for people to own as itís dirt cheap and pretty reasonably good. If someoneís able to take a couple close-up pictures of the scale with a flexible measuring tape, Iíd be very grateful. Given one side I should be able to figure out the other one.
    According to my research the correct aperture scale is (someone please correct me if Iím wrong) 0011.064. The mounting holes on my shutter are 65mm apart (for the larger of the two scales, that is).

    Also, if anyone has use for the scales that are on here (0013.055, I see this scale on a Caltar II-E 210mm f6.8) Iíd let them go for cheap.

    Click image for larger version. 

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  2. #2

    Re: Caltar II-N 210mm f5.6 aperture scale help

    Just as a point of reference, I have had a set of 210mm f/5.6 Symmar-S cells in a Caltar II-E 210mm f6.8 shutter for ages shooting as is with zero exposure issues. I was shooting chromes with it for architectural jobs to boot. But to be clear, I never shot at wide open (as one can imagine) so the widest opening was just for focusing and I would close down to whatever (f/22/f/32 on the native aperture scale matching the meter) and fired away.

  3. #3

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    Re: Caltar II-N 210mm f5.6 aperture scale help

    That’s a good point... I would still like to make an aperture scale, but I’ll go ahead and use it for now. I did notice that f/64 on the scale doesn’t line up with the narrowest aperture of the lens (the lens stops down a bit further past the f/64 mark). But I’m shooting colour neg so not a big deal to overexpose.

  4. #4

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    Jul 2012
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    46

    Re: Caltar II-N 210mm f5.6 aperture scale help

    I'm curious about this too. I have the same shutter with the same markings, with matching 210/6.8 lens cells. BUT, I sometimes stick my orphaned Symmar 150/5.6 cells in the shutter.

    I had been under the impression that I could derive the actual iris diameter from the focal length / f-number and use that to calculate the f-number for the other lens (in this case, f/11 on the 210 scale is 19.09 mm, which would be f/7.8 for the 150 scale) but it didn't quite work. I have to stop the lens down 1 2/3 stops further than my numbers say to. I wish I understood why. Maybe it's because the cells are different? It might work for you though.

  5. #5

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    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by devb View Post
    I'm curious about this too. I have the same shutter with the same markings, with matching 210/6.8 lens cells. BUT, I sometimes stick my orphaned Symmar 150/5.6 cells in the shutter.

    I had been under the impression that I could derive the actual iris diameter from the focal length / f-number and use that to calculate the f-number for the other lens (in this case, f/11 on the 210 scale is 19.09 mm, which would be f/7.8 for the 150 scale) but it didn't quite work. I have to stop the lens down 1 2/3 stops further than my numbers say to. I wish I understood why. Maybe it's because the cells are different? It might work for you though.
    Be much easier to just order scales from Rodenstock and not tell them that itís for a Schneider lens. Just tell them 150 Apo Sironar in Copal 0.

  6. #6

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    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by Theo View Post
    .... I did notice that f/64 on the scale doesn’t line up with the narrowest aperture of the lens (the lens stops down a bit further past the f/64 mark). But I’m shooting colour neg so not a big deal to overexpose.
    It's the same scale for the Caltar E and Caltar N as long as they're both for a 210mm lens. One is marked to 5.6 and one to 6.8! Nearly all shutter apertures close beyond the narrowest aperture of the lens because shutters are not made for specific lenses!
    Last edited by Luis-F-S; 5-Feb-2020 at 18:32.

  7. #7

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    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by devb View Post
    . Maybe it's because the cells are different? It might work for you though.
    No, it's because the focal length is different. One is a 210 FL, the other is a 150!

  8. #8

    Join Date
    Jan 2019
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    116

    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by devb View Post
    I'm curious about this too. I have the same shutter with the same markings, with matching 210/6.8 lens cells. BUT, I sometimes stick my orphaned Symmar 150/5.6 cells in the shutter.

    I had been under the impression that I could derive the actual iris diameter from the focal length / f-number and use that to calculate the f-number for the other lens (in this case, f/11 on the 210 scale is 19.09 mm, which would be f/7.8 for the 150 scale) but it didn't quite work. I have to stop the lens down 1 2/3 stops further than my numbers say to. I wish I understood why. Maybe it's because the cells are different? It might work for you though.
    f-number is focal length divided by apparent diameter of the aperture as viewed from the front. The apparent diameter can be different from the physical diameter of the aperture. Sometimes the front cell magnifies the aperture opening very little, sometimes it's significant, it depends on the lens design. I think you're talking about a 210mm Caltar II-E and a 150mm Symmar, which are two different designs, so that might matter. You can try measuring the apparent diameters with a ruler across the front of the lens.

  9. #9

    Join Date
    Jul 2012
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    46

    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by Luis-F-S View Post
    No, it's because the focal length is different. One is a 210 FL, the other is a 150!
    Yes, which is how I calculated a different f-stop for each focal length even though the aperture diameter was the same. N = f/D

  10. #10

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    Re: Caltar II-N 210mm f5.6 aperture scale help

    Quote Originally Posted by reddesert View Post
    f-number is focal length divided by apparent diameter of the aperture as viewed from the front. The apparent diameter can be different from the physical diameter of the aperture. Sometimes the front cell magnifies the aperture opening very little, sometimes it's significant, it depends on the lens design. I think you're talking about a 210mm Caltar II-E and a 150mm Symmar, which are two different designs, so that might matter. You can try measuring the apparent diameters with a ruler across the front of the lens.
    Ah, that makes sense. I'll try it out and see what I get. Thank you!

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