Aperture scale on Isconar 180

I am starting out to actually use an half-old (1930's from what I can gather) "Jos. Schneider Co. & Kreuznach Doppelanastigmat Isconar" lens, and the aperture scale progression always throws me a bit: f:6.8, then 9, 12,5, 18, 25, 36 and the 50 as the smallest stop.

Would that (sort of, leaving out the first 6.8), correspond to f:9 being f:11, and then 16, 22, 32, 45, and on to f:64?

It seems like a nice lens, but I need to dial in the process a bit, since I am using it with a lens cap - rather low contrast negatives even with a rotary process.

No, the aperture scale is what it is. The list has a link to a spreadsheet that will make things clearer. Look at the column headed Congres 1900.

Which meter do you use?

Thanks, Dan - forgot to look in the list - of course! :)

I am using a Sekonic L308s and in the future do FP4+, rated at EI 50, but I guess since I am using a lens cap (unless I find a LUC shutter or similar that is small enough) the exposures anyways will tend towards overexposure.

As an aside, I had a look at my LUC shutter (a no. 4) and now I see that I might be able to kludge some rubberband or something onto the lens to make it fit (a few millimetres missing).

I've never looked at an L-308 or an L-308 user manual, but I have one for my humble L-328. The L-328 reads in half stop increments, which will get you close enough, especially since you can interpolate between marked stops when setting the aperture.

Dan, the L308 series meters read out in tenth-stop increments.

Thanks, Oren. So the OP can see exactly what he needs.