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Channels

The Footage, Composition, and Layer panels allow you to view the individual red, green, blue, and alpha channels of an image. Color channels appear as grayscale images in which the degree of white corresponds to the color value. You can also view the color channel using its own color. The alpha channel appears as a grayscale image as well, where the degree of white corresponds to opacity. As you may recall from Chapter 2, you can even view the unmultiplied color channels—that is, the color channels without the alpha taken into account. For more about alpha channels, see the Chapter 2 sidebar "Alpha Bits: Understanding Straight and Premultiplied Alpha."

To show individual channels:

  1. In a Footage, Composition, or Layer panel, click the Show Channel button vwr_channel.jpg , and then choose the channel you want to view ( Figure 3.77 ):
    03_77_alphamenu.jpg

    Figure 3.77 Click the Show Channel button, and then select the channel you want to view.

    RGB vwr_channel.jpg —Shows the normal image, with visible channels combined. Red vwr_channel_r.jpg , Green vwr_channel_g.jpg , or Blue vwr_channel_b.jpg —Shows the selected channel as a grayscale. Alpha vwr_channel_a.jpg —Shows the alpha channel (transparency information) as a grayscale. If active, the transparency grid is disabled while Alpha is selected ( Figure 3.78 ). See the next section, "Viewing Transparency."
    03_78_showalpah.jpg

    Figure 3.78 Choose Alpha to see the alpha channel.

    RGB Straight vwr_channel_s.jpg —Shows the unmultiplied RGB channels. If active, the transparency grid is disabled while RGB Straight is selected.
  2. To show the selected channel depicted in color, select Colorize ( Figure 3.79 ).
    03_79_colorize.jpg

    Figure 3.79 To see the selected channel in color, select Colorize from the pull-down menu.

    The Channel pulldown menu's icon changes according to the current selection.
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