geesbert Posted March 7, 2011 Share #1 Posted March 7, 2011 Advertisement (gone after registration) I am confused: when did Leutz use mm or cm for their focal lengths? why did the change it? Link to post Share on other sites More sharing options...
Advertisement Posted March 7, 2011 Posted March 7, 2011 Hi geesbert, Take a look here mm or cm. I'm sure you'll find what you were looking for!
luigi bertolotti Posted March 7, 2011 Share #2 Posted March 7, 2011 They started in mm (see the first Leicas with Anastigmat/Elmax, and the first Elmars), changed to cm in the first years of '30s : Elmars went on till 1934 (or so) marked as 50mm, while "new" lenses like Elmar 9 cm, Hektor 7,3 cm are engraved in cm even in items of 1931. Then, they changed again to mm around late '50s (don't know if there has been a precise date of transition... one can have some hint looking at the Summicrons 5cm/50mm in that timeframe). Why they did so ? Well... about the postwar transition, one can observe that the International Standard of Measurements (SI) , adopted just around the end of '50s, considers the METER as the basic unit of length, with the derived units that go at steps of x1000 or /1000 (Kilo- , Milli- / Mega-, Micro- etc...) ; the previous standard was the so called CGS system (Centimeter, Gram, Second) which endured a bit more in USA. Leitz probably wanted to endorse the new standard... probably the whole German Industry was "politically" encouraged to do like this. Link to post Share on other sites More sharing options...
jc_braconi Posted March 7, 2011 Share #3 Posted March 7, 2011 on 1934 double use of mm and cm next use of cm, on 1958 double use of cm and mm next use of mm. Link to post Share on other sites More sharing options...
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