355 G-Claron in 210mm Copal 3 Shutter

[neil poulsen]

I purchased my 355mm G-Claron from Kerry Thalmann, and he picked the best of his 355mm G-Claron Barrel lenses and mounted it directly into a Copal 3 shutter with an aperture scale marked for a 210mm lens.

For all my lenses, I measure the shutter accuracy for each speed and have a table that gives a correction (if needed) for each speed in stops. In this way, I can pick a speed and then make an aperture adjustment to correct for shutter inaccuracy. In particular for the 355mm G-Claron, I included the aperture correction for the fact that the aperture scale on the shutter was meant for a 210mm lens, versus a 355mm lens.

I'm thinking that this Copal 3 Shutter together with the 355mm G-Claron lens should have the same coverage as any 355mm G-Claron mounted in a Copal 3 shutter that has the correct aperture scale.

This seems obvious to me. But to my question, is this correct?

[Robert Opheim]

I may not understand your question. I would think that a #3 shutter whether it has whatever aperture scale mounted on it would have the same coverage. Now if you have front mounted the lens on the shutter, it might cut off some of the coverage - by mechanical vignetting. I am not knowledgeable about front mounted lenses - the possible vignetting could be calculated.

The method of exposure that you are using is very different than the method I use. You have a wonderfully accurate tested shutter speed chart that you correct for with an aperture adjustment. You set the shutter speed and then set the aperture. I typically first set the aperture and then set the shutter speed - as I have been using the G Claron 355mm lens for close-up work, and depth of field and diffraction are what I wrestle with.

[neil poulsen]

. . . You set the shutter speed and then set the aperture. I typically first set the aperture and then set the shutter speed - as I have been using the G Claron 355mm lens for close-up work, and depth of field and diffraction are what I wrestle with.

Yeah, that's what I was thinking. It's the same shutter with just a different aperture scale. So, same coverage.

Were I doing closeup work, I would do my best to be aperture priority. I would try to get the best combination of aperture and shutter speed that I could, and yet still have accurate exposure. But even with an accurately adjusted shutter at all speeds the same is true. One can only adjust the shutter to within a stop, and then one selects the best aperture within those constraints.

Thanks for your response.