Swapping a lens and shutter

[Robert Ley]

I recently picked up a late model (circa 1967) 120mm Angulon f:6.8 in great condition except the Prontor press shutter has some problems. Today I bought a 210mm f:6.8 Rodenstock Geronar in a nice looking black Copal #1 shutter. What I would like to do is swap the lens elements of the Geronar with the Angulon. My question is, will there be any issues that I must deal with and will the aperture scale be accurate.

[Jim Galli]

You should be able to swap group for group in that shutter. Measure the length while it's in the old shutter with a good caliper. Then when it's in the new shutter re-measure. It should be the same exactly. Your aperture scale will be off. The nice thing about a Copal though is that each step on the scale is exactly the same distance. So if you have one "known" you have them all. When the 210 scale is indicating f 11 1/2, the 120 will be at f8. Hope that's not too confusing.

[Ernest Purdum]

It would be a pleasant but unlikely coincidence if the Geronar aperture scale worked for the Angulon, You could get a little idea by looking in the front of each lens. The closer to each other the aperture at f6.8 appears to be, the less the discrepancy.

You will probably need some assistance from the S.K.Grimes firm (www.skgrimes.com). Be sure to send both lenses and shutters.

[Capocheny]

Robert,

In addition to what Jim and Ernest said... S.K. Grimes does a great job at calibrating the f-stop scale to the lens opening. They can either scribe the scale directly onto the shutter or onto a scale, which is then attached to the shutter.

They did a first class job on my 360 f6.8 Symmar... and it didn't even take them all that long to complete the job. :)

Cheers

[Ole Tjugen]

I can promise you that the aperture scale will NOT match!

A 210mm lens needs a little less than 31mm opening for f:6.8, a 120mm lens will need a little less than 17.5mm. That is ssuming the same distribution of lens power between the front and rear elements of both lenses, which in this case happens to be close to correct.

[Dan Fromm]

Um, Henry, about those aperture scales that attach to shutters. I b'lieve they come from the shutter manufacturer. At any rate, on one of my visits to Woonsocket I saw rolls of them. Need a scale? Cut it off the roll ...

Cheers,

Dan