Shooting Blue- or Green-screens

The client wants to shoot an actor against blue or green-screen with some markers, and insert him/her into a 3-D environment. Anything to look out for?

Beware of the client zooming in for the head shot, and taking most/all the trackers out of the frame. You need to keep 10-12 in view for a decent track (mathematically there can be many fewer, but that doesn't make it a good idea.)

The pure blue/green-screen shots are dangerous because the background is so featureless that if you mess up and have trackers out of frame, you can wind up in big trouble. There's a tendency to put some marks on a back wall way behind the actor, focus on the actor, and wind up with a very flat shot with little to no perspective on the tracking marks. When this is the case, a 2-D track is the right/only approach (using SynthEyes's tripod mode). The tracking marks are out of focus, sometimes to the point of invisibility, making the situation worse.

For a higher probability of success, you want the shot to encompass the presenter from a distance, so that tracking marks can be seen not only on the back wall, but on the floor and possibly side walls, depending on camera motion. Having trackers visible at a variety of depths makes tracking much more sane. You don't have to use every tracking mark, so feel free to have plenty. Odds are that a moving-camera shot will move the field of view around so that only a fraction of them are visible at a time, unless it has been carefully planned. If there's a desk or other props in the scene, that can be helpful, as long as you make sure it has some trackable features. 

You can have trackable features mounted on light stands, or hanging from the ceiling if they aren't waving in the breeze.

The best tracking mark is a small square or circle the same color as the screen, but darker. You can still key it out, but SynthEyes can still find it. Be sure to test your setup in advance of the main shoot to make sure the marks aren't too small or too close to the background to be visible if they are out of focus or washed out a bit.

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