The DEPTH Workflow - 3D Postproduction: Stereoscopic Workflows and Techniques - page 161

5.7.3 Depth Grading is Subjective
Depth is the most arbitrary part of 3D. There are a few rules, of course. But,
like color grading, depth grading is a subjective process. You might want
the audience to feel the size and distance of a wide shot of a landscape by
pushing it back, or you might want them to appreciate tiny depth cues by
bringing it closer to the screen, or even animate that depth so it makes the
viewer converge further or closer away, to prepare them for the next shot.
For me, depth grading is very similar to color grading and I usually approach
it in the same way. First, make it technically correct and then make it feel
right with the action and the story.
• Use depth to direct the viewer. Remember the most comfortable point of
the whole 3D volume is the screen plane (i.e., zero parallax). If unguided,
the audience will look there i rst. You can use it to your advantage to
place there the object of interest in the shot. Also, remember when you
change from one shot to the next the audience's eyes will be converged
at whatever point catches their attention in the previous shot. Use this
to your advantage. If you are editing a dialog with close-ups of two
characters, it helps to place the object of interest at the same depth to
reduce convergence adjustment between shots.
• Use depth to prepare the viewer. If you are going to have a very deep
shot with something of interest in the background, you can animate the
convergence on the previous shot to “drag” the audience's eyes to the spot
you want them to look later in the shot. This can also work if you want
something to pop-out and surprise them. Get them to look far i rst and
then throw them something (in negative Z-space)! They will most likely
jump in their seats, since they were not ready for it.
• Play it over and over again. I said before that depth grading is very
similar to color grading and I truly believe it. If I want to see if the color
of a sequence is right, I play it over and over to feel if any of the shots
have color “bumps.” With depth it's the same thing. Play sequences over
and over again to feel the smoothness (or lack of it). If you are tired, take
a break or ask somebody else to check it out and see how they feel. If
you are working on a shot-by-shot basis and you can't play several shots
together, you are just not depth-grading right. Find a way to play your
work. Render a lower quality version, burn a Blu-Ray and take notes, do
anything. Not everyone can afford to post on a high-end real-time system,
but it is very important that you i nd a way to see your shots in context.