Video matting from film via the Ultimatte can also avail itself of the screen-correction feature. To use this attribute, a take should be prepared of the blue-screen scene exactly as it will be shot for the production, with a locked-off camera but without any of the live action. If the scene requires camera moves, a motion-control system should be provided for the camera, and the calibration take run with the motion-control program for each shot. No further changes should be made to such motion-control programs unless another calibration take is also made.
In the postproduction compositing process, the calibration take will be used to "map" the blue-screen area and correct for any deficiencies. Thereafter, actual production takes will use this information as a reference and correct the deficiencies for all subsequent takes. The main advantage of this procedure is to lessen the burden on the stage crew in providing effective matting backings, thus speeding setups and reducing costs. Permitting this technology to become a panacea, however, entails risk; if the Ultimatte is unavailable or the calibration take is unusable for any reason, it will then be difficult to fall back on more conventional techniques. The result will be very costly and time-consuming to overcome. It's a good idea to make screen-correction calibration takes while also making every reasonable effort to provide a functional blue screen in the original photography, relying on the screen correction only as an insurance policy.
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