View Full Version : Need help - Berthiot Perigraphe 90/F14 Wide Field

8-Jun-2010, 08:03
I recently got a Berthiot Perigraphe 90/F14 for my 5x7 format. But I don't how to read the aperture setting. It has a dial set aperture setting with marks "14, 20, ..." I don't know how to convert them to normal aperture reading, such as "16, 22, 32, 45, ..." Would like to seek some help in the forum.

Jim Noel
8-Jun-2010, 08:11
You list 14, 20. What are the next two numbers in sequence? I suspect they are 28, 40. If so, they are f-numbers using a different scale.

8-Jun-2010, 08:28
You are correct. The next two are 28, 40. But I can not read for the last one, which is probably 56. How to use the f-number scale correctly and linked to our current light meter readings?

8-Jun-2010, 09:20
I found I posted in the wrong segment. I should re-posted onto the "lenses and accessories" section.

Ole Tjugen
8-Jun-2010, 10:06
The numbers really are f-numbers. Berthiot preferred basing the scale on f/10 rather than the more common (to us now) based on f/1. some others went to f/100, so that stops were marked 13, 18, 25, 35, 50, 70, 100...

So take your f/14 to really be f/14, or about half a stop more open than f/16.