3D Depth Continuity and the Stereographer

By: Clyde DeSouza

(image copyright: the movie, Haunted 3D. used for educative purposes only. click each for larger)

Stereoscopic 3D Depth Continuity:

In traditional 2D movie making the task of maintaining continuity from scene to scene is that of the Script Supervisor (and Director). This includes “depth” as well. For instance, if a scene features a person walking down a road into the distance, the next camera angle can’t show the person to have traveled half way down the road in a matter of a couple of seconds, unless this is done intentionally as part of an effect of speeding time.

But again in 2D movies, it’s easy to cheat depth. That’s one of the ways those stunts involving a person crossing a railroad track at seemingly the very last second while a train approaches. The use of long lenses compresses depth and makes it look like the train is a lot closer than it actually is.

In Stereoscopic 3D, this is very near impossible to do. The one thing that stereoscopic 3D movies give us, is the ability to record and present “Spatial information” or the depth dimension of a location.

Take a look at the two images above. They are from (in our opinion) a well made 3D Bollywood movie, Haunted 3D. The stereographer, Brent Robinson has done an excellent job throughout the film in maintaining depth continuity along with other S3D best practices. While it can be said that he has been conservative with the depth budget throughout the movie, in hind sight, the movie works in both the cinema and on a typical 3DTV without causing any harm to the audience.

S3D Depth Continuity is more than just Cut matching:

In the scene above, both the shots “match” in depth continuity in a number of ways:

1) The actual “deepness” of the corridor match in both shots shown at two different times in the movie (one way to ensure this, is of course to shoot all scenes involving a particular set, at the same time)

2) This means that the lens settings are the same

3) The Interaxial and /or toe-in (convergence) if any, is noted and re-applied when shooting at the same location.

3) That the time taken to travel the distance is approx the same depending if the character or camera is previously shown as running or walking.

That example is by no means the only scenario to show Depth continuity. There are many other depth continuity scenarios that need attention. Now take a look at the images below:

(image copyright: the movie, Dark Country. used for educative purposes only. click each for larger)

The image above is a severe breach of Depth Continuity in a single take. It is not a cut but an actual tracking shot around the main characters, but the depth abruptly bounces due to an interaxial change. Thus the entire depth of the scene gets disturbingly changed.

Another example of a depth mismatch is in cuts. In the pictures above, the first shows the same scene with one 3D depth setting, this then cuts to a solo shot of one of the characters speaking, and then cuts to the second image above, showing a completely different depth. This is another example of no Depth Continuity.

Depth Continuity – The Script Supervisor’s Job? The DPs or the Stereographer?

That question is open to debate at this stage of 3D movie making, as there is still an unsettled question of how much importance should be allotted to a Stereographer. As time goes by and more experience is gained, it’s natural that the DP would want to take charge of the entire composition of the 3D “frame”. We use the word frame in quotes because today in 3D filmmaking, a lot of established terms are open to new interpretation. At Real Vision we prefer to call the “frame” the window, because that’s what the frame becomes… a window into 3 dimensional space.

Getting back…should the script supervisor be in-charge of the depth script as well as the movie script? or should the depth-script then be in the hands of the DP, and can he/she also pay attention to maintaining depth continuity in addition to his/her other tasks.

Simple depth continuity as in the scene above can be accomplished to a certain extent in post by H.I.T. but again, HIT can only solve for scenes such as the one above, which does not contain too many foreground objects that may otherwise cause disturbing stereo window anomalies.

Depth Script Design and Implementation:

As 3D movie making evolves, one debate that will soon be over is whether there is a need for a stereographer or not. We would argue yes, there is a need. For the very same reason that there is a need for a 1st and 2nd AC, as well as the need for a Best Boy and Gaffer… for the smooth running of 3D film shoot, a stereographer is certainly recommended for this one reason alone: The designing and implementation of a Depth Script (comprising depth budget of scenes, taking care of depth continuity during shoot and in post with the editor) and many other 3D related tasks.

Can these jobs be offloaded to the script supervisor or DP?  Yes, in indie productions one person fills many shoes, but in a well planned (and financed) 3D feature, the depth script should be with the Stereographer who sits with the Director and DP during a shoot, and with the Editor in post.

(image copyright: the movie, Drive Angry 3D. used for educative purposes only. click each for larger)

The Edit, Editor and Depth Continuity:

In the scene shots above taken from the movie Drive Angry, the image on the left shows …

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