Lens element specs (Congo)greenspun.com : LUSENET : Large format photography : One Thread
Some time ago I posted questions regarding mounting a set of Congo 180mm lens cells in a shutter. I was able to get a response from Yamasaki Optical regarding this. The following was their response:
"Thank you for your inquiry. If the lens elements were mounted on a Copal NO.3 shutter, the distance between the front and rear flange is 28.6mm. The serial number record was already lost,we can't say which design was adopted for the lens but possibility is that the distance between the lenses facing a iris diafragm is 11.37mm.
Best regards Keizo Yamazaki Yamasaki Optical Co.,Ltd. firstname.lastname@example.org "
Does anyone know why the distance between cells would be different for an iris (barrel) vs a Copal #3 ? Or am I not understanding this?
-- Matt O. (email@example.com), August 26, 2000
Matt, It appears to be two different measurements. The first measurement is from the front to rear of the lens, outside measurement. The second would be the seperation of the elements at the diaphram when mounted in a shutter.
-- Doug Paramore (firstname.lastname@example.org), August 26, 2000.
Hi Matt - I would suggest calling Steve Grimes, he probably has first- hand experience with those lenses. He's usually very helpful on the phone.
-- Wayne DeWitt (email@example.com), August 26, 2000.
Well, I finally got an intelligible reply from Yamasaki. To wit:
"If your lenses were shutter mouted then you need no adjustment for Copal No.3 shutter with mount screw of 56mm diameter. But for another type of Copal No.3 with mount screw of 58mm diameter you need some work on the cell. If your lenses were barrel mounted you need some work on the cell to keep surface distance facing the iris diafragm at 11.37mm.
If your front cell wear engraving "Commercial Congo",then it was mounted on a Copal No.3.
Best Regards Keizo Yamazaki "
As my elements say "Commercial Congo", I am now in need of a 56mm dia. thread Copal #3. Any leads?
-- Matt O. (firstname.lastname@example.org), August 28, 2000.