Goerz Berlin Weitwinkel Lynketoskop f-scale

[Richard Årlin]

Goerz Berlin Weitwinkel Lynketoskop front element and damaged iris only, focus seems to be some 8". I thought I could try the single element just for fun at least with a packard shutter on my 5x7. I know how to calculate the actual f.stop, what puzzles me is the curious scale engraved on it.. 24-48-182-384-768. Kinda weird huh ? Any hints from someone ?

Richard

[Linas Kudzma]

I also own a tiny Goerz Berlin Weitwinkel Lynketoskop (approx 120mm focal length) that is similarly engraved. I've found a table that compares various old diaphragm numbers to modern f-stops which gives the following:

Goerz 24 = f16 (modern)

48 = f22.6

383 = f63.25