Digital Video - April 2008 - (Page 33) THE 300ULX COMBO SYSTEM Designed for use with today's smaller DV cams, the system (300UPR receiver, 30BT bodypack, and 30XT plug-in transmitter), is loaded with features, and is our smallest wireless mic system yet. ground right next to the foreground subject. Adjust the tolerance until the background of that hue and value around her is transparent; but don’t worry about the shadow or darker areas yet. Adjust the choke (shrink) and blur controls to get a clean edge — generally you want to apply as little choke and blur as possible. Now, apply a second instance of the chroma keyer and use the eyedropper to select a darker area of green in the shadow. Adjust the tolerance until that area is transparent; again, don’t worry about the darker areas at the edge yet if they are still messy. Adjust the choke (shrink) and blur controls to get a clean edge. If the darker edges are still opaque, apply a third instance of the keyer, use the eyedropper to select a representative area of darker green, and adjust the tolerance to make it transparent. As long as the darker green is not actually matching the dark green of her sweater, you’ll be able to pull an acceptable composite. Scroll through the entire scene, watching for areas where the background becomes visible or appears as excessive noise; or areas where the model’s sweater turns partially transparent. You may have to adjust tolerance on one of the instances of the filter a bit more to clean these up. The difference between this approach and simply using a single filter with aggressive settings will not always be visible on a single frame, but will be more noticeable with the subject in motion. That’s where the aggressive settings may create sizzling or odd-looking edges, requiring excessive blur. When each of the filters can deal with a limited range of hue and value, using lower choke/shrink and blur settings, you’ll be able to create a more pleasing and conwww.dv.com Above: On the far left, we see the garbage matte has cleaned up the left side of the shot and taken away the darkest area of green backing. The first application of the color keyer has been adjusted to key out the fully lit green. In the center, another instance of the keyer is adjusted to take out the model’s shadow. On the right, the final composite, with a third instance of the keyer adjusted to remove the darkest green areas. Left: While the model is properly lit, the greenscreen is not. The combination of darker areas on the screen and a poor wardrobe choice make this shot impossible to key cleanly with a single application of the stock color keyer in your NLE. sistent edge to the foreground subject and better control the way the foreground plate blends with the background. The final composite isn’t ideal; for better results you’ll need a higher-end third-party keyer such as Keylight, Ultimatte AdvantEdge, Zmatte or Primatte. So what happens when it’s worse than this shot, for example when a piece of wardrobe is almost exactly the same color as a dark area of the backing color? That’s when you’ll need to step up to a full compositing program and use the same concepts to create multiple regions of transparency, and combine them with keyframed motion masks to create the final composite. And that’s when you will be able to hang out a shingle as a compositor! DV Rev. John Jackman has been involved in video production since the last energy crisis (when Carter was president). He has created special effects on a number of programs and is the author of “Bluescreen Compositing: A Practical Guide for Video & Moviemaking” (2006, Focal Press). dv april 2008 • 240 UHF user-selectable frequencies • Digital LCD display with multi-functionreadout • Twin high-gain antennas • Balanced mini-plug output with locking connector • Supplied mini and XLR output cables • 30BT comes w/EX-503L lapel mic with lock-down mini connector • Includes shoe-mount on receiver, metal belt-clip on 30BT • Powered by 2 “AA” batteries (not supplied) (Available without the 30XT as the 300LT system at new lower prices!) Carrying case included with 320ULX system ® P.O. Box 10, Franklin Square, NY 11010 (516) 328-7500 • FAX: (516) 328-7506 For full specifications e-mail azdenus@azdencorp.com or visit our Web site: www.azdencorp.com 33 http://www.azdencorp.com http://www.azdencorp.com http://www.dv.com
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