The DEPTH Workflow - 3D Postproduction: Stereoscopic Workflows and Techniques - page 138

IA for any given shot depends on choices made during production. The greater
the interaxial, the greater the distance between L and R. Changes in IA increases
or decreases the perceived “roundness” of objects. This stands to reason: if
your eyes are farther apart you have a better view of the sides of an object.
IA has only a very narrow range in which objects in a scene look normal in
terms of scale and roundness. Increasing interaxial can make objects in the
scene seem miniature in comparison with their actual size. Decreasing interaxial
can cause the effect of making objects look gigantic. This miniaturization or
enlargement may or may not be desirable from a creative standpoint. Typically,
interaxial is set on a shot-by-shot basis, although in some cases, teams (such as
those recording live events such as music concerts) choose to modify interaxial
on the l y.
Unfortunately, there are a limited number of things you can do in post if you
have an interaxial issue (i.e., things look too large or too small in relation to
the viewer). The reason is not at all mysterious. Assuming two imagers, each
imager acquires only part of a scene (the part that it can “see”) from its specii c
viewpoint. So if the imaging system did not see it, there is no easy way to
create the new information you need without turning to 2D-to-3D conversion.
In limited cases, you may be able to adjust interaxial after the fact with some
advanced i nishing tools using various optical l ow and interpolation technologies.
Generally, however, changing IA signii cantly in post is typically time-consuming
if it is possible at all in any given case.
“It's important to realize that people have different preferences
in creating and viewing 3D. Some are less sensitive to artifacts
and extreme transitions in depth. Or they want to stretch the 3D
beyond what is realistic. My personal preference is to have the 3D
on the realistic side. Sometimes if the 3D is too big, you are always
trying to i nd yourself in the space or you are always aware that
you are on a ride. For me 3D is much more gripping emotionally
when you forget you are watching a 3D show. To use a volleyball
analogy, the 3D sets up the ball; it is up to the other toolsets like
color to spike the ball over the net.”
—Dave Franks