Mounting jig - Reply - Part II

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

>(I use) cardboard mounts that are blue on the
>inside.  I check how each pair of  slides look in my viewer after I
>position them.  Sometimes I make adjustments but only by how it looks to
>me.  I am not measuring anything nor do I have a clue how to go about
>that.  

I do the same thing and I am not measuring anything either.  I mount by eye
in Albion and RBT mounts.

There is one measurable quantity that is of importance, especially in
projection.  This is the maximum on-film deviation, which is the separation
of the furthest object in the scene, minus the separation of the closest
object.  The maximum recommended value of this separation is usually 1.2 mm
(on 35 mm film).  If you look at your mounting gauge you will see that
there is a set of vertical lines that mark this maximum deviation.  You are
instructed to keep your "infinity" objects within these lines.

You can measure this infinity separation directly off the screen during
projection by measuring the offset of the most distant objects.  It is
important that this offset is less than 65 mm (approximate separation of
the eyes).  Projection can also be used to check alignment.  It is usually
easier to see things when magnified and superimposed on the screen than
directly off the mounts using a mounting gauge.

You do not have to worry about this maximum deviation if you are following
the rules... With a regular stereo camera you should not place objects
closer than 7ft from the camera, if infinity is included in the picture. 
You can come closer than 7ft but then you normally have to block the
distant objects and use close-up mounts to set the window properly.  In
hyperstereos, the 1/30 rule (and other more sophisticated formulas) aim
to control this maximum deviation.  Again, it is in projection where this 
becomes an important issue.  Excessive deviation can be better tolerated 
in a viewer.

Bottom line:  Relax and continue doing what you are doing now!

Long live 3d!

George Themelis


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End of PHOTO-3D Digest 2388
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