Anaglyph Movies (Cont)
Some of these steps can be combined, but only if the conversion software is flexible. Usually, however, even more steps are required. For example, human eye separation is usually around 2.5 inches. Getting two video camera lenses this close together is quite a challenge. One way to solve this dillema is to flip one of the cameras for a closer fit. The custom rig that I built shown on the next page uses this technique to bring the two camera lenses closer together. A drawback of this method is that one of the videos needs to be flipped during as part of the deinterlacing process, or as a separate stage.
If a beam-splitter is not used, then the biggest challenge in creating an Anaglyph video still remains. Frames taken by the video cameras are captured at about 1/30th of a second apart. While this seems very short, the truth is that if two cameras are not synchronized precisely, video of subjects in motion cannot be turned into a convincing anaglyph. The rig below utilizes a dedicated device called a LANC Shepard to synchronize the two cameras. I have found that a synchronization of better than 1/600th of a second is required for success given subjects with average motion. To capture highly dynamic stereo scenes, finer synchronization is required.
In order to increase the odds that two video cameras are sufficiently synchronized for motion capture, they should be of the same make and model. It helps if they are made from the same production batch. Still, compensation for inconsistencies within the electronic parts may be performed by the synchronization device. For example, the LANC Shepard can be instructed to immediately turn on the slave camera when the master camera is turned on. Further, it can delay the slave startup timing by a user-specified amount if synchronizing the two devices requires compensation.
Remember to zoom out to the same macro view on both cameras before capturing the video. Image stabilization can ruin the stereo effect, and needs to be turned off. Also, use an object with a flat surface (e.g., a CD) to check that both lenses are perfectly aligned with each other.