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g Ultimatte allows you to use a "clean plate" with your chroma key shots, which works

6 similarly to a difference matte of sorts. An exact locked-off shot of the blue-screen

& background and environment is taken without objects or actors. More often, this is o z used with blue or green painted environmental objects that shadows will be cast on or

KE that the actors will interact with in the final composite. This Clean Plate layer is then

§ used in Ultimatte to produce a more accurate matte.

w The three sources are imported into After Effects and placed in the Comp or on the

TA Timeline, with the foreground chroma layer on the top and the Clean Plate layer hidden or beneath the background layer. You must first select the preview and Clean Plate layers os before launching the Ultimatte AdvantEdge application by choosing Effects > Ultimatte >

£ AdvantEdge (Figure 9.9). When the Ultimatte effect is applied, the Effects palette appears.

Note: Ultimatte will not allow you to mix resolutions or sizes of background and foreground layers for preview.The background and foreground layers must be the same size and resolution to allow previewing the composite in the application. If they aren't the same size,a warning dialog pops up telling you so.

You reset crop lines by dragging them from the outside edges of the image window in to where you want to crop the matte (Figure 9.10). Make sure you don't crop into the live action areas of a moving subject.

Use the Sample Backing Eyedropper in the Screen mode to select the initial background chroma color from the chroma foreground layer. When looking at the matte, you'll notice that not all of the blue is selected at the first pass. If you use the Add Overlay tool and select those areas that have holes in the mask, then the keyer will include that range of pixels in the creation of the matte (Figure 9.11). If too many pixels are selected too close to the objects in the scene, you'll need to use the Remove Overlay tool and select the areas that bleed over onto the image.

Figure 9.8 Ultimatte AdvantEdge has advanced controls for handling details,shadows,transparency,and color matching.

Figure 9

Using a Clean Plate layer in Ultimatte AdvantEdge, you can retain many of the chroma keyed background's shape and shading.

Figure 9

Using a Clean Plate layer in Ultimatte AdvantEdge, you can retain many of the chroma keyed background's shape and shading.

Figure 9.10

Set the outer edge crop to create a large garbage matte reference.

Figure 9.10

Set the outer edge crop to create a large garbage matte reference.

If you click the More button, advanced settings will pop up from the bottom of the screen; select the Inputs tab and make the Clean Plate layer visible (Figure 9.12) to see your preview. In my example, the details and shadows on the building now show up, and there's a clean composite around the young woman.

Figure 9.11 Select the background color with the Sample Backing Eyedropper, and fill in the missing areas with the Add Overlay tool.

Figure 9.12 Turn on the Clean Plate layer to complete the composite.

Figure 9.12 Turn on the Clean Plate layer to complete the composite.

You can do a comparison between the final composite and the original foreground layer or mattes at any time, either by selecting the dual-screen button on the bottom left of the user interface or by selecting the split-screen button and dragging the handle back and forth on the screen to see the preview (Figure 9.13).

Figure 9.13 Two different previews are available:dual-screen and split-screen modes.

Figure 9.13 Two different previews are available:dual-screen and split-screen modes.

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