[LargeFormat] Compur #1 and Copal #1 for G-Claron 305mm f9

[Michael Briggs]

On 22-Jan-02 Clive Warren wrote:
> Am now a very happy bunny :-)  Just picked up a 305mm f9 G-Claron in 
> barrel at a very reasonable price and also have a spare Compur #1 
> sitting here waiting for it.
> 
> My question is to all those of you who may have the lens in a Copal 
>#1 shutter which is what they are usually supplied in from the 
> factory. What is the width of the shutter between front and back for 
> the lens elements and are there any spacing rings used on the 
> elements?

It will likely work by directly screwing into any reasonably modern #1 shutter. 
If you can measure accurately, measure the total length of the lens in the
barrel and in the #1 shutter.  If they are the same, it is ok.

According to a datasheet that I have, and confirmed with a measurement, the
thickness of a Copal #1 press shutter is 20.000 +/- 0.025 mm.  This is the
distance from the front edge of the thread for the front cell to the back edge
of the thread for the rear cell.  The other mechanical specs are quite tight:
these two surfaces are to be parallel to 3 arc min and the centers of the
threads aligned to 0.03 mm.

S.K. Grimes has drawings of Copal shutters with measurements on his web site.

--Michael