P3D Re: beginner 2x2 mounting

[George Themelis <gthemelis@xxxxxxxxx>]

--- John Asbacher <asbacher@xxxxxxxxx> wrote:
> When you are mounting 2x2 slides does the "near point" ALWAYS
> overlap?
> 
> what happens if you shoot an object that is supposed to be
> far away, like the top of a building. Are you allowed to
> create a false near point that is not visible on the slides?

Yes John.  Your question does make sense.  The short answer is
that you can create a false near point as you say.  How much? 
Depends on your personal preference.  Experiment.

The longer answer involves an understanding of the two
philosophies of stereo slide mounting (both apply equally well
in 2x2 and 41x101 slides):

#1: Mount to infinity:  You mount the pair so the infinity
objects are offset by a fixed amount.  Then the near points will
fall where ever they may.

#2: Mount to the window:  You mount the pair with the near point
at window level (or overlapping - per your terminology) and let
the infinity points fall where they may.

If the stereo pair contains a healthy amount of depth (something
like 7ft to infinity for Realist format) then both methods give
the same final results.  Differences arise when you have "too
much" or "too little" depth.  

If there is too much depth (i.e. you have placed your near
object too close to the camera) then the first method will
result in a "window violation", i.e. the near object will be in
front of the window (not necessary a violation if planned that
way).  The second method will result in too wide separation of
the infinity points.  This might matter or might not.  It
depends on the image.

If there is too little depth then the first method will result
in a big "gap" between the stereo window and the scene.  The
second method will result in infinity objects with smaller
separation, which generally is not objectionable.

Because of this last statement, most stereo workers prefer
method no. 2.  They adjust the stereo pair with the near object
close to the window (or going through if allowed) because they
feel that this gives the most pleasing results.

If the scene has really very little depth then even people that
use method no. 2 will not put their scene at window level but
behind it some distance (the false near point you described) to
increase the sensation of depth.

Hope this helps!

George Themelis


=====
George Themelis (DrT-3d@xxxxxxxxxxxxxxxx)
__________________________________________________
Do You Yahoo!?
Thousands of Stores.  Millions of Products.  All in one place.
Yahoo! Shopping: http://shopping.yahoo.com