4
Preproduction Decisions
The essential decisions regarding I/O and convergence are often made in preproduction.
While errors in convergence can be relatively easily corrected in post, misjudgments in
setting the interocular are not so easily fixed. The I/O and convergence decisions for a
film may be incorporated into a
depth script
, a graph that tracks the filmmaker’s
intentions for the emotional impact of the scenes. In terms of convergence, if a filmmaker
wishes the audience to be drawn into the action on screen, the scene may be shot with
strong positive parallax (staging the key action beyond the screen plane). But if a
filmmaker wishes the audience to experience discomfort, the scene may be shot with
strong negative parallax (staging the key action in front of the screen plane). In the same
way, emotionally-neutral scenes may be shot with zero parallax (with the key action
staged on the screen plane). These
depth decisions
may be codified in the shooting script
with marginal notations such a C-5, C-1, C-0, C+1, C+5, etc.—where C-5 refers to a shot
with lenses strongly converged, pushing the key subjects far into the viewer’s space; C-0
refers to a shot with unconverged (parallel) lenses, placing key subjects on the screen
plane; and C+5 refers to a shot with lenses moderately converged, pulling the viewer into
the screen space.
In terms of I/O, the use of wider-than-normal and narrower-than-normal camera
configurations, as noted above, can introduce unwanted distortions. However, the
informed use of exaggerated interoculars can help filmmakers enhance the impact of
their stories. A wider-than-normal interocular might be used to emphasize the relative
insignificance of a character compared to the character’s surroundings, while a narrower-
than-normal interocular might be used to exaggerate the importance of a character
relative to the character’s surroundings. As with the depth decisions noted above, these
scale decisions
may be incorporated into the depth script, taking the form of a curve that
tracks the variation in the strength of these values over the running time of the film. In
the same way, the scale decisions may be codified in the shooting script with marginal
notations such as I-5, I-1, I-0, I+1, I+5, etc.—where I-5 refers to a shot in which the lenses
are narrowly separated, making key subjects look larger than life; I-0 refers to a shot in
which the lenses are separated by the average human interocular (2.5”), making key
subjects look the same size as they do in life; and I+5 refers to a shot in which the lenses
are widely separated, making key subjects look smaller than they do in life.
Fig.4 – Depth Script
