Since when Leica changed to F2, 2.8, 4

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Early Elmar 50/3,5 lens has German aperture series with numbers like f6.3, f9, f12.6 etc. Any one knows when Leitz changed to the more commonly used f5,6, f8, f11 series ?

-- martin tai (martin.tai@sympatico.ca), January 10, 2002

Answers

Laney sez 1946 they changed to "international standard" - 3.5, 4, 5.6.... he has picture of pre-war lens with German scale - late post- war lens with modern scale.

-- Andy Piper (apidens@denver.infi.net), January 10, 2002.

Thank you Andy, Aperture scale with 1, 1.4, 2, 2.8,4,5.6, 8..... was used in most pre war Zeiss Ikon cameras. It seems that this scale was a Zeiss invention.

The start number 1 was a good choice, for aperture diameter = focal length, and also the sqrt(2) relationship between the consecutive stops is evident from 1 to 1.4

The Leitz scale of 3.5, 4.5, 6.3,9, 12.6 ... was a not as elegant, and it is not clear what was the beginning number and why it was selected

Apparently Leitz followed Zeiss reluctantly

-- martin tai (martin.tai@capcanada.com), January 20, 2002.


The first aperture scale was proposed by Franz Stolze:

1.1, 1.6, 2.2,3.3,4.5, 6.3,9,12.5, 18,25,36,50,71, 100

Later in the mid 20s, the following scale appeared:

1,1.4,2,2.8,4,5.6,8,11,16,22,32.45,64,90

Now all cameras use the last one-- international scale.

The ratio of one number to the next, in both scales is equal to square root of two.

Apparently, the Stolze scale began with 100, and succesively divided by sqrt(2) to 71, 50... down to 1.1 While the international scale goes the other way, begins at 1, and succesively mulitply by sqrt(2)



-- martin tai (martin.tai@capcanada.com), January 20, 2002.

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