This in turn has an effect on fine detail such as motion blur and hair, so these areas (hands, hair) may require their own holdout mattes.Ī holdout matte isolates an area of an image for separate treatment. It's used when preservation of edge detail is of utmost importance-in other words, typically (but not exclusively) when working with footage that was specifically shot to be keyed against a screen of blue or green.įigure 14 A quick diagnosis of Keylight's first pass at this shot: The shadows must be keyed out because they extend outside the garbage matte area (and right off the set). Keylight is typically employed to a back-plate shot against a uniform, saturated, primary color background. You wouldn't use Keylight to pull a luminance key, however, or when simply trying to isolate a certain color range within the shot its effectiveness decreases the further you get from the three primary colors. For example, you can use Keylight for removal of a murky blue sky ( see Figure 11). Keylight is useful in many keying situations, not just studio-created bluescreen or greenscreen shots. ![]() The competition has by no means disappeared (I personally remain a big fan of Primatte), but Keylight is part of After Effects, so it's the main focus of this article. Its reputation was already well established prior to its inclusion in After Effects, having even earned it a Technical Achievement Award from the Academy of Motion Picture Arts and Sciences. It provides the exact methodology that was used for early digital composites, which themselves mimicked optical compositing methods.īeginning with version 6.0 Professional, an alternative was included free with After Effects: Keylight. ![]() Its methodology is fundamental and can be replicated using basic channel math and Levels controls. When I label Color Difference Key "pedestrian," I speak as someone who matted hundreds of shots with it, back before After Effects offered alternatives.
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