We had initialy planned on installing a two-wall hard-cove cyc, however it's been our experience that audio quality is compromised on a hard-cove set. In addition to audio reflections, hard-coves can have problems with lighting reflections. We decided instead to go with fabric screens for better audio and maximum versitility. To switch from green to blue, it's just a matter of changing fabrics. We don't have to re-paint and wait for the paint to dry. Our green screen is a 15' x 20' plush lightweight foam-backed fabric from The Rag P'ace, Hollywood's premier source for motion picture technical fabrics. It's deep digital key color is Optic Geen Tempo. Our blue screen is a 10' x 20' muslin.
An LED light ring around the lens provides the only illumination for the retro-reflective screen.
Green Screen by Candlelight:
If the shots don't require head-to-toe coverage including floor, we have a 10' x 10' retro-reflective screen. With the duel-color LED light ring around the lens, we can switch colors instantaneously with a flip of a switch. One of the big advantages of using this system is that the screen doesn't have to be lit with conventional lighting. The screen is only illuminated by the small amount of green or blue light emitted by the LED ring. This fact enables a lot more flexibility in lighting your foreground image, as in this candlelight example.
The screen contains millions of tiny glass beads imbedded in the fabric which reflect the LED light on axis back into the lens. If one is standing next to the camera lens in a lighted room, the screen will simply look like grey fabric. However, if you view on axis through the camera's lens, the background screen is bright green as shown in the frame-grab at upper-left. Click on the clip at lower-left to watch the green screen replaced with background footage of an oudoor patio fireplace at night. Shooting a scene like this with only candlelight would not be feasable with a traditionally lit green screen because there would be too much ambiant spill light on the set from lighting the screen. The only lights on this set were the candles, the green LED ring around the lens, and for a flickering firelight effect, a small LED light about the size of an iPhone called the "Kick". The Kick can be used stand-alone, or it can be controlled by an iPhone. In order to emulate the fire in the background plate flickering on the model in the foreground in this demo, I used the Kick iPhone app to control the light which was placed out of frame behind the model. By playing a video clip of the fire in the Kick's iPhone interface, I was able to sample portions of the firelight by pointing my finger at different areas of the fire in the video. In other words, I used a video clip of the fire outdoors in the patio's fireplace to control the color and flickering effect coming from the Kick light in our green screen studio.
For those who want to learn more technical details about this process, read on...