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If the lighting levels in the source shot change significantly over the duration of the shot, it can cause the planar track to lose tracking and wander off. One of the major causes of this is that the flat surface being tracked can suddenly catch a glare from the sun or on-set light, and blow out the exposure a bit. Often this entails not just a light- level change, but a change in colors as well. There are a number of ways to address shots exhibiting this issue.
First, you can periodically set a key on the pattern, if you are satisfied with the track on that frame. The planar tracker will use the most recent keyed frame as a reference, so you can set new keys that gradually accommodate the change in lighting. See Re-Keying the Pattern for more information.
Second, you can try the Uniform setting of lighting compensation, on the planar control panel. Under this setting, SynthEyes tries to adapt to signficant changes in lighting level between the reference and tracked frame. This setting is not without costs, however: depending on the imagery, it might throw off tracks that would otherwise succeed, and it adds a substantial amount of CPU time. So we advise using it only on specific shots that might benefit from it.
Third, you can use the high-pass filtering capability of the image preprocessor (hit 'P' to open it quickly). Adjust the Hi-Pass spinner on the Rez tab. This is not entirely convenient since it affects the images totally, as stored in the RAM cache, you'll be able to see only the high-pass image.
With the high-pass option, the image will be less affected by the changes in lighting. Of course, a good portion of the image is gone too, so there is less information to track! Be sure to set all planar trackers' detail mode to High, when using high-pass filtering.
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