The principal advantage of the rear-illuminated screen is the instant uniform illumination obtained at the flip of a switch. Unfortunately, few studios have permanent facilities for large back-lit screens. A front-illuminated blue-painted surface is also acceptable for traveling matte photography. It has the advantage of availability. Any smooth surface that can be painted, including flats, a canvas backing, and so forth, can be used as the blue backing.
An increasingly popular illuminator for front-lit screens are arrays of the special-purpose blue fluorescents described above. Tine broad, soft-light nature of fluorescents makes it relatively easy to illuminate screens of 100 feet or more in width. More care must be taken to eliminate spill illumination on front-lit screens. With care, front-lit screens can produce a result every bit as good as back-lit scenes.
Blue screens can also be front-lit with blue-filtered HMI or Carbon Arc Lamps. Getting even illumination with these sources is a time-consuming challenge, and filters must be carefully watched for fading. Photographic results are good to fair. Least desirable by a large margin (for film purposes) is a blue surface front-illuminated with white light. White light, however, is essential when the actor and his shadow must appear to enter into the background scene.
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