non-standard f-stops?

[cbass]

I've got a 1939 collapsible Summitar 50/2.0 that I'd like to start using on my FED-2. Before I do, I'm hoping to get some help with understanding the "non-standard" aperture progession in this lens. The Summitar stops are marked:

2/2.2/3.2/4.5/6.3/9/12.5

Do these stops correspond with the "standard" progession of:

2/2.8/4/5.6/8/11/16?

My hand-held meter reads the standard progression and I want to make sure I don't get poor exposures when I use it with the Summitar-equipped FED.

Of course, I may simply be able to meter with the fool-proof "Sunny 12.5" method! 😉

Thanks.

 

[ray_g]

I am not familiar with the shutter speeds on the FED, but the old f stops work particularly well with cameras with the "old" shutter speeds, like the barnacks and earlier M3's. This might help:

http://www.ozdoba.net/leica/schraub_altezeit_e.html

 

[Toby]

If what I read in the website is correct the f stops are 1/3 stop slower than todays progression in most cases. You can introduce a 1/3 of a stop correction by changing the iso on the meter ie 400 film becomes 320. Then use the stop one smaller than standard ie

2.8 on the meter = 3.2 on the camera
4=4.5
5.6=6.3
8=9
11=12.9

that should give you correct exposure

 

[simonankor]

I have a 1939 FED 1 with the f/stop progression 3.5/4.5/6.3/9/12.5/18...

I just use the "Sunny 18" rule. Since the speeds on the FED 1 are different to the current norms as well, it usually works out well. I think the speeds are (from memory) 20, 30, 40, 50, 100, 200, 500.

Haven't missed a shot thus far! 😀