Maybe here? en.wikipedia.org/wiki/Renard_series
"R10"/3 (2 ... 8000) in white numbers
Aug. 30, 2026
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In the R20 series we can find the standard set of f/numbers ...
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Sometimes photographic equipment does not comply with that series and there is no particular reason it should that I know of. For example, the well-known Weston Master light-meters have f/44 marked on a dial but there is no such preferred value in any R-series. Ho hum ...
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But ISO 517 for actual lens markings has a full-stop list going from 𝑓/0,5 to 𝑓/128 which is mo' better, I reckon ... said list indeed has 𝑓/45 but not 𝑓/44.
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There is a calculation for theoretical 1/3-stop f/numbers which is based on a ratio of the sixth root of two.
I compared theory with what my camera says on the LCD as I scroll upwards with the un-marked control wheel through the mounted lens range ...
... spot the deliberate mistake ...