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

[Theo]

I’ve 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 it’s mounted in has an aperture scale for an f6.8 lens.
I’d 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 it’s dirt cheap and pretty reasonably good. If someone’s able to take a couple close-up pictures of the scale with a flexible measuring tape, I’d 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 I’m 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) I’d let them go for cheap.

[fuegocito]

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.

[Theo]

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.

[devb]

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.

[Bob Salomon]

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 it’s for a Schneider lens. Just tell them 150 Apo Sironar in Copal 0.

[Luis-F-S]

.... 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!

[Luis-F-S]

. 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!

[reddesert]

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.

[devb]

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

[devb]

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!