Stereoscopic Video

Posted by Mike McCarthy on February 2nd, 2011 filed in Industry Status

3D Movies have been all the rage ever since Avatar came out and made a ton of money.  ”3D” has risen and fallen in popularity multiple times in the past, but it looks like it is here to stay for now.  The point of no return will be reached when auto-stereoscopic (no glasses) displays are widely available at reasonable prices.  In the meantime, certain sectors of the market will have opportunities to push the limits of the technical envelope with stereoscopic production.

Stereoscopic video is basically just video with separate streams for the left and right eye, and the viewer’s mind interprets the differences between those angles as perceived depth.  There are three main technical challenges presented by stereoscopic production.

The first step in the process is to generate and record two separate images of similar but different perspectives.  This is usually solved with specialized hardware, by using rigs to mount two narrow cameras in parallel, or using a beam splitter to record two similar perspectives with larger cameras.  Recently there have also been cameras released that have multiple lenses as an all-in-one option.  Ideally both the separation between the lenses and the angle at which they converge should be easily controllable, especially for live recording, since those two values have a significant impact on the final stereoscopic effect.  The other acquisition option for content generation, is to render two separate perspectives of a computer generated 3D animation.  This requires no special hardware, just a few changes to the software and settings, plus a doubling of render time and storage  space.

Depending on the acquisition approach, there are a number of extra steps in the post process.  Both angles must be matched together, synced down to the frame, and usually muxed in some fashion.  Eventually they need to be aligned, the convergence needs to be set, and there may be a color shift from the beam splitter that needs to be compensated for.  Any visual effects will be much more challenging as well.

Finally there is the issue of displaying separate images to each eye from the viewers perspective.  This can be achieved with separate miniature screens for each eye, or more frequently, by finding some way to filter out the opposing view from each eye, from the combined image.  This can be done with color filters, polarizationalternating shutters, or lenticular screens, to control the image that each eye sees.  Ideally there need to be ways for the stereoscopic effect to be previewed immediately on set, examined during the post process in the edit rooms, and delivered to the final target audience.  This makes display solutions the first logical aspect to be examined, even before camera options.  The basic ideas behind many of these viewing options will be discussed in the next post.  Following that, we will examine some of the other practical ramifications imposed on the post-production process by stereoscopic projects.

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