Shutter equivalent to Copal #0

[Kevin Crisp]

The f:6.8 90mm angulon WAS available at the end of production in a Copal 0 shutter FYI. Serial number in the 11 range.

[Dan Fromm]

Dan, can you explain more fully what you mean. I am afraid I don't follow.

Eric

Eric, there's an iris diaphragm in the shutter. And there'll be an aperture scale on the side of the shutter or on the face plate, depending on which shutter it is. The numbers on the aperture scale (8, 11, 16, ... for an f/8 Acugon) indicate diaphragm settings at which the opening's diameter is 8/(diameter of the lens' entrance pupil) and so on.

When a shutter is delivered with a lens in it the aperture scale will be correct for the lens. Change the lens, as your seller did, and there's no guarantee that the aperture scale will be correct for the replacement lens. If the aperture scale is incorrect and you set aperture and shutter speed as your light meter or rule of thumb ("sunny 16") advises the film won't see as much light as you intend.

Oh, and by the way, there's a law of nature to the effect that a freshly-purchased used shutter's speeds are off. Another source of exposure problems. All freshly-purchased used shutters need at least calibration with a shutter speed tester and at best an overhaul.

[eonore]

Dan, please pardon my stupidity, but I have never handled a large format lens. Wouldn't setting f8 on the shutter produce an f8 aperture? What does it mean when you say that the aperture scale is correct for the lens? Does the lens have its own scale which must be matched somehow to the shutter scale?
I hope I am not missing something obvious. Thanks for your help.

Eric

[eonore]

Dan, please pardon my stupidity, but I have never handled a large format lens. Wouldn't setting f8 on the shutter produce an f8 aperture? What does it mean when you say that the aperture scale is correct for the lens? Does the lens have its own scale which must be matched somehow to the shutter scale?
I hope I am not missing something obvious. Thanks for your help.

Eric

I think I have answered my own question. If the lens that is now attached to the shutter has a different exit pupil diameter than the lens originally shipped with the shutter, the apertures may vary from the scale. Since I did not build in the expense of sending the lens and shutter for an overhaul, I am thinking of punting on this deal and finding one where the lens and shutter match.

[Dan Fromm]

You sort of got it. Its the entrance pupil, not the exit. And no matter what you do, if you buy a used lens in, naturally, a used shutter the shutter will be guilty until proven innocent. Budget for an overhaul.

Or shoot a high latitude b/w film and you'll be able to get away with exposures several stops off. I shoot mainly reversal film, which is very fussy about exposure.

[eonore]

Thanks Dan, you've really helped.