[pure-silver] Re: correction for bellows extension
- From: "bonner" <bguil@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 4 Mar 2015 13:07:15 -0500
Michael,
For bellows length, are you measuring from front standard to ground glass?
-----Original Message-----
From: pure-silver-bounce@xxxxxxxxxxxxx
[mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Michael A. Smith and
Paula Chamlee
Sent: Wednesday, March 4, 2015 11:59 AM
To: pure-silver@xxxxxxxxxxxxx
Subject: [pure-silver] Re: correction for bellows extension
It is real simple: Total length squared divided by the focal length squared
gives you the factor to multiply the exposure by.
Example: If you have a 12" lens and the bellows is out 20" you have 400 divided
by 144 for a factor of 3. Being exact with this is not critical.
While the actual measurement is from the rear nodal point of of each lens to
the other rear nodal point (and the rear nodal points are not always in the
center of the lens, just measure, as Richard Knoppow wrote, from center of lens
to center of lens. (This holds with view camera lenses.)
Michael A. Smith
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