355 G-Claron Lens Cell Spacing

[cdholden]

I was able to source a Copal 3 shutter for my 355mm G-Claron which as been living in a barrel mount. The lens cells fit the Copal 3 shutter the same as the barrel.
I recall reading somewhere that the spacing is different between the two versions, but can't seem to find any reference online.
I'm looking for the distance from the front of the front element to the back of the rear element. In barrel mount, it is 80mm for this distance.
Do any of you have a factory mounted 355 G-Claron in shutter that you could measure for me?
Thanks,

Chris

[Tracy Storer]

Measure the length of your barrel, if it's different from the thickness (at the threads front and back) of a Copal #3, you have your answer.

Mine in Copal is 79.6+mm, but I don't think it's an original factory mount and my current measurement method isn't ideal.

[Steve Goldstein]

I have a PDF downloaded from the Schneider Archive site for these lenses in shutters. It gives the overall length as 79.7mm. The printing date was August 1998. It's here:

http://www.schneider-kreuznach.com/archiv/pdf/gcn.pdf

An older (1982) brochure for barrel mount versions also gives 79.7mm as the length. That's this one:

http://www.schneider-kreuznach.com/archiv/pdf/gcn_82.pdf

[Steve Goldstein]

When I looked at the older brochure a little more closely I noticed that it actually gives data for both barrel and shutter mounts. The shutter-mount lengths match those in the 1998 publication. The only lens that has different lengths for the two mounts is the 150mm, all the other focal lengths list the same overall length for either mount.

150mm: shutter = 34.7mm, barrel = 36.2mm

210mm: shutter = barrel = 49.0mm

240mm: shutter = barrel = 53.5mm

270mm: shutter = barrel = 60.8mm

305mm: shutter = barrel = 68.9mm

355mm: shutter = barrel = 79.7mm

[Tracy Storer]

Good get, Steve.

[cdholden]

No doubt... and a good one for the archives.
Thanks Steve!

[Steve Goldstein]

One thing to keep in mind is that the documents don't say anything about whether a spacer is needed for one mount or the other to achieve the correct overall length, or possibly the spacing(s) to the iris.

[Lachlan 717]

Chris,

I'll get the digital calipers onto mine today to show you the ring-to-ring distance. It might help...

[cdholden]

I was reading an analog caliper. I'm sure it's good at "80ish". It would be hard to get fractions on it.
Thanks anyway.

[Dan Fromm]

Chris, your 355/9 G-Claron is probably a plasmat type. If so, you shouldn't worry.

A while ago I innocently mounted a set of 150/5.6 Boyer Saphir BX cells in an ex-Polaroid CU-5 Copal Press shutter. Turns out that these shutters don't conform to the Compur/Copal/Prontor #1 shutter standard, their tubes are around 0.3 mm longer than the standard.

When I measured and found this out I asked my friend Eric Beltrando to see what that increase in cell spacing would do to the lens' performance. Eric has written a ray tracing program, you can read about it and many lenses on his site www.dioptrique.info. He replied that the error in spacing was 0.2% of the lens' focal length, that plasmats -- that's what the BX is -- aren't very sensitive to small spacing errors, and that I shouldn't worry.

So enjoy your lens and stop worrying.

[cdholden]

Dan,
No worries here.
I am usually of the mindset that anything worth doing is worth doing right the first time, I'm good with using a lens cap for a shutter, but so far I have less than $20 involved in this upgrade. A faster shutter makes using TMY a little easier. For my less than $20, I plan to measure and notch off a few marks on the iris for my own calculations and call it a good deal... until I get around to sending it off for a proper iris engraving.
No worries here, just an inexpensive upgrade!

[Lachlan 717]

Dan,
No worries here.
I am usually of the mindset that anything worth doing is worth doing right the first time, I'm good with using a lens cap for a shutter, but so far I have less than $20 involved in this upgrade. A faster shutter makes using TMY a little easier. For my less than $20, I plan to measure and notch off a few marks on the iris for my own calculations and call it a good deal... until I get around to sending it off for a proper iris engraving.
No worries here, just an inexpensive upgrade!

Chris,

PM me your address (again) and I'll copy the f-stops from my Copal. Might save you a bit of time...

[Dan Dozer]

Hi Chris,

My 355mm G-Claron is serial #14040207, is mounted in a Copal 3, and does not have any spacers.