Wollensak Alphax f-Stop Markings For 15inch f5.6

Recently, I picked up a Wollensak 15 inch f5.6 lens, the kind pulled from old aerial cameras, thats been attached to a Wollensak Alphax #4 shutter. I'd like to start using the lens, but the only issue is the shutter does not have the f-stops marked. Anyone have any tips on how I could figure out and mark the f-numbers, or perhaps someone has a similar lens and I could copy their markings?

If you have a measuring caliper it should be fairly simple.

 

Assuming the opening in the shutter is equal to maximum aperture, then halving the opening diameter is equal to a 2 stop reduction of aperture. Dividing the iris diameter by 1.414 (root 2) gives a one stop reduction.

 

Spend a couple of minutes with a calculator to make a table of diameters, use the caliper to set those diameters and then mark the appropriate pointer positions on a paper label stuck over the aperture scale.

 

Once you have this template you can make a more 'professional' looking version from it - if necessary.

 

BTW, sub-millimetre accuracy is totally unnecessary for the larger apertures. It's only photography, not rocket surgery!