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pacemaker cam list and focal length discrepancies
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AuthorMessage
kwmullet
Joined: 17 Dec 2003
Posts: 6
PostPosted: Wed Dec 31, 2003 12:16 am

Concerning the cam list at
http://graflex.org/speed-graphic/top-rangefinder-cams.html:

I remember reading somewhere that many of the odd focal lengths
(136.4, for instance) are due to the fact that the labeled local
length and the actual focal length on several lenses differ.
When shopping for lenses, it's difficult to know which focal
length refers to which lens. Is there a version of this list around
somewhere that gives which lens is which in these cases?

The large format / graflex lens lists/documents on the site seem to
list only the labeled focal lengths.

A tengential question would be, short of seeing it in a actual specs,
how can one tell when the true focal length of a lens varies from the
stated focal length? Is there a way of calculating this from angle of
coverage or some other stat?

Advance apologies if this has been asked and answered before, but a
look through the site archives wasn't helpful in finding an answer for
me.

-KwM-
45PSS
Joined: 28 Sep 2001
Posts: 4081
PostPosted: Wed Dec 31, 2003 2:02 am

Take said lens to an Optical Testing Lab or a shop with such equipement and have it tested. No other way to know.
Charels
Les
Joined: 09 May 2001
Posts: 2682
PostPosted: Wed Dec 31, 2003 2:30 am

This is one of the problems of using cameras from a defunct company. When you bought a lens, they matched the cam to the lens for you. Now with the supply small and scattered you could look for years and not find an exact match.

I'm still working on finding a way to quickly, easily, and accurately measure the exact focal lenght. An optical bench is nice, but the smallest are 9 meters long and weigh in the area of several regulation billiard tables. Not something that the wife or the 100 year old house approves of in the living room.
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