FORMULA clarified

["Paul S. Boyer" <boyer@xxxxxxxxxxxxx>]

John Bercovitz has alerted me to the fact that the Kitrosser's formula in 
my last note was expressed in a manner which could be confusing.  He 
correctly deduced that it is
(0.0635*w)/(F*W*I) = 1/d-1/D
where w is the width of the negative or diapositive, F is the 
lens-to-film distance, I is the interlens separation, d is the distance 
to the nearest object, and D is the distance to the farthest object in 
the field of view.  (All distances in meters.)  W is a constant, set by 
Kitrosser at 1.52; I think that in actual practice it should be  more 
like 1.25.
If you wish to have objects at infinity in your picture, then 1/D = 0.  
If the window is at 2.1 m (as in the Realist), set 1/d at 0.476. Then
w/F*I = 9.374
For full frame, w=0.036 m;
for European format, w=0.031 m;
for Realist format, w=0.023 m.
[Sorry to load the Digest with another message.  I'll try to be more 
careful next time.]
--Paul S. Boyer
New Jersey, USA
<boyer@xxxxxxxxxxxxx>


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