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View Full Version : How to read old american f/stops.....



Torsten
4-Mar-2008, 15:33
Hi, could somebody please explain me how to translate the following f/stops written on the barrel of an old american Petzval:

1 2 4 8 16 22

Thank's a lot in advance

Torsten

drew.saunders
4-Mar-2008, 15:59
Here's the answer from 1899:

http://en.wikipedia.org/wiki/F_stop#Aperture_numbering_systems

Easier: 16 = 16 and work your way back/forward from that.

Eric Biggerstaff
4-Mar-2008, 16:08
US f/stop
1 = f4
2 = f5.6
4 = f8
8 = f11
16 = f16
32 = f22
64 = f32
128 = f45
256 = f64

Torsten
4-Mar-2008, 17:02
thank's a lot!!