P3D Mounting of Stereo Prints, a century old (and longer )Problem

[Bob Wier <wier@xxxxxxxxxxxxxxxxx>]

Here's a message from Bill Walton which got diverted...


|From: BILL3DBW3D
|To: photo-3d@xxxxxxxxxxxxxxxxx
|Subject: Mounting of Stereo Prints, a century old (and longer )Problem
|
|I could make a long list of people who are much better qualified to
|discuss mounting of stereo prints than I am, Paul Wing, Stan White, Bill
|Patterson, Craig Daniels and Brandt Rowles, to name a few.  But I don't
|believe that any of them are P3d members so I will attempt to clear up a
|couple of questions that have been asked about mounting.  These are my
|opinions, tested by working on them for a long time, but they are not
|necessarily "the gospel"
|
|. Mounting close up prints made with a stereo camera- Usually the
|information contained in the two negatives is not the same, due to some
|optical law I guess. If the prints are printed commercially it may be
|necessary to radically trim them to fit the stereo window.  This means
|that you throw out the idea of 3" prints, use the print with the smallest
|amount of information on in it and trim the other print so that the
|stereo window is correct.  You may need to trim both prints and  you can
|conceivably end up with a very small image in both prints, but the stereo
|window will be correct.  I would not be concerned about how the small
|prints look on a 3 1/2 x 7 stereo card,  Most stereoscopes have a built
|in magnification that will assist you in your viewing.  As far as the
|image being to close or to far from the window that can be adjusted by
|moving the images apart or pushing them together.  Again we are talking
|about trimming both images to allow this to be done.  
|
|For those of us who print our own pictures, not only BW, as we have a few
|members in the SSA who do quality color printing,  we have another option
|with close up negatives made with a stereo camera.  If I want to have the
|images 2 7/8 inches wide (this is my usual width) I print the negative
|with the least information(subject matter if you will) to that size. 
|Then I print the 2d negative that size and crop if for the stereo window
|to match the first image..  In my favorite stereo camera, a 3.5 Realist,
|the left negative always has less information than the right one, when I
|make close up stereographs.  So I print the left negative then the right
|and crop the right one so that
| the stereo window is correct. And I may have to do some trimming if I
|misjudged on the printing
|
|Over the years there have been several figures quoted as being the "best"
|separation between distant points on a stereo card. The numbers that come
|up the most frequently are 75-80mm.  This seems to be a comfortable
|distance for most people although there are some "visual athletes",
|including me, who can fuse up to 100mm in a stereoscope.  But this
|distance will cause problems for most people so I think it is best to
|keep the 75 to 80mm separation between distant points.  This in itself is
|not fatal and I would think that someone who measures stereographs and
|then complains is getting a bit picky.  But to achieve this 75-80mm 
|separation may require some trimming of the prints again, as well as
|placement on the card.
|
|I strongly encourage everyone who wants to improve their stereo card
|mounting to:
|
|A.  Read the two mounting articles in Stereo World  written by Bill
|Patterson and John Dennis.  These two articles
|were published in 1979 and 1984.  Read the mounting article written by
|Stan White in the PSA Journal in 1996.
|
|B.  Join a stereo card circuit as I really believe this is the premier
|method to learn correct stereo card mounting.  There are 8 card circuits
|in the SSA and one in the PSA.  NSA membership is a requirement to join
|the SSA Circuits and PSA membership is a requirement to join the PSA
|Circuit.  For SSA Membership contact Shab Levy , 6320 SW 34th
|Ave,Portland OR 97201.   For PSA Stereo Card Circuit Information contact
|me at the EMail address below.
|
|Again, this is considerably more than my 2 cents worth
|
|BILL C WALTON
|bill3dbw3d@xxxxxxxx
|--------- End forwarded message ----------
|



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