[LRflex] Little to do with Leica, but interesting photographic measurments....

All:

Last week a friend gave me photocopies of the relevant pages from 
several articles on Calotypes, Daguerreotypes, Heliography, etc., from 
"A Dictionary of Arts, Manufactures and Mines" (A. Ure, 1860) .

It's fascinating reading, but in the Daguerreotype article (p 567) the 
author talks about Voigtlander lenses and their apertures.

"Voigtland's lenses consist of two achromatic object-glasses, the first 
nearest the object having an aperture of 18 lines, the second on of 19 
lines; the solar focus of the two is 5 1/4 inches."

and later:

"Voigtland has recently made a camera with two object-glasses, as above 
arranged, each having an aperture of 37 lines"

I inquired on a scholarly, photo history list, to which I belong, and 
discovered that "lines" are a botanist's measure, there being 12 lines 
to the inch. So the first lens has an aperture of 3.08 inches and a 
focal length of 5 1/4 inches... or an aperture of f 3.5! Not bad for the 
1850's!

I you're interested in more on odd, imperial units, check out:  
http://www.gwydir.demon.co.uk/jo/units/length.htm.

-- 
David Young,
Logan Lake, BC    
CANADA. 

Personal Web-site at: http://www3.telus.net/~telyt
Leica Reflex Forum web-page: http://www3.telus.net/~telyt/lrflex.htm

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