P3D David White's lens testing

[John Toeppen <toeppen@xxxxxxxxxxx>]

But how much can they be off and still have a tolerable system? To look
at
it another way, how well and to what degree were lenses used in some of
the
more popular stereo cameras matched. I, for one would be interested in
learning how David White and Eastman Kodak tested their lenses. Does
anyone
know? I know that Eastman was extremely careful in their procedures, but
I
do not know what they tested for specifically.

RM

I worked with a Realist tooling engineer (Ron Jakowsky)who built some
the fixtures for assembly and test.  The lenses were tested for
resolution and focal length.  They were then sorted by focal length
picked as pairs from the bin of the same fl.  Unmatched lenses will
produce images of the same size if held the same distance from the film,
however, one will not be in the same focus as the other.

The Graflex stereo was awful; the lenses were fixed but were focused at
different distances, 6 & 25ft.  The Kodak has helical focus where the
focal length and the position of the lens in the barrel must be set.
Kodak had to do this with fixturing as it is difficult to do this task
without such an aid.

 The Realist with it's drive shaft and parallogram linkage allowed the
lenses to be fixed in the front of the camera.  An test image was viewed
from an artificial infinity focused by the camer's lenses on a screen
set in the film plane and examined under magnification.  This was to
assure that the film plane was perpendicular to the lens(s) axis.

I bought parts from the artificial infinity setup used for this
procedure.  One of the mirrors was an offaxis parabola of a 160" fl and
10 1/2" in diameter.  I am still looking for a practical use for that. 
I also got some of the lens test photos of resolution targets, photos
testing depth of field, photos of the Wisconsin Sound building in which
the David White Labs were located in '47.  Sometimes John Willis would
take his photos around his home or down in the rail yards.  Once he had
placed a Revere Lens in one side of the camera and a Realist lens in the
other.  They tested everone's lenses against their own.  They would
shoot though an old lens and one from the new coating batch to know if
they could mix stock. Maybe John Willis wanted to go home early once or
twice and shoot some photos along the way.....

John Toeppen
http://home.pacbell.net/toeppen/


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