copal #0 shutter question

[mark_5047]

I have a 90mm/copal#0 rodenstock 4x5 lens that the shutter failed, so i bought a mint/new 150mm rodenstock to take the copal#0 from and when I went to switch them out I noticed that the 150mm had an additional spacer ring on the front. It looks like it snaps in.

My question is how does it come out?

any info would be great, the 90mm's diameter is too great to fit inside this spacer and the spacer is not on my old 90's shutter or on my new 65mm lens either.

I can post photos if that would help.

THanks, mark

[Jim Rice]

It just snaps out.

[Thilo Schmid]

Mark,
the "spacer ring" is a tuning ring that was installed in the factory to perfectly tune the lens elements and the barrel. The mechanical components of a lens can have slight manufacturing tolerances. You cannot know if these tolerances are within the lens elements of your 150mm or in the barrel or in both. This tuning can only be done on an optical bench at the factory. Try your lens with and without the tuning ring. If you are not satisfied with the performance of either, you should send it to the factory.

BTW: it is not sufficient to switch the aperture scales on the shutters. The mechanics has to be adjusted as well.

[Jim Rice]

Any 'tuning' that was done results in a shim (in the case of my 90 Gradagon, between the front cell and the shutter). Copal shutters are made to very close tollerances and it's simply a fact that some lenses use the plastic ring that you descibe and some don't. I replaced the Copal 0 on my 90 with a brand new shutter from B&H for ~$150 and had to remove the plastic thingy. If you paid more than that for the 150 you might consider that route and keep the lens intact.