I'm trying to figure out the aperture scale on my Volute shutter, from what I gleaned
here and elsewhere f16 is the same on the Unified Scale ( US ) as on a modern lens
and I need to double it or divide ( ? ) to get the modern equivalent.
The lens cells are marked 12 and 18 in ( Gundlach - Manhattan Optical ) so I'm guessing its
a Turner Reich design and it's a convertible and there is probably a missing cell since the
aperture scale has three scales.

The aperture numbering has me scratching my head, since there is no f16, how would I convert
them to modern f-stops ? any guidance is appreciated.

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