Applying the Linear Color key

The following procedures provide a basic overview of how to use this effect.

To apply the Linear Color Key:

1. Select a layer as the source layer, and then choose Effect > Keying > Linear Color Key.
2. In the Effect Controls window, choose Key Colors from the Key Operation menu.
3. Choose a color space from the Match Colors menu. In most cases, use the default RGB setting. If you're having trouble isolating the subject using one color space, try using a different color space.
4. In the Effect Controls window, choose Final Output from the View menu. The view you choose appears in the right thumbnail and in the Composition window. If you need to see other results, work in one of the other views:
• Source Only shows the original image without the key applied.
• Matte Only shows the alpha channel matte. Use this view to check for holes in the transparency. To fill undesired holes after you complete the keying process, see Matte Choker (Pro only).
5. Select a key color in one of the following ways:

Note: To use eyedroppers in the Layer window, choose Linear Color Key from the View pop-up menu in the Layer window.

• Select the Thumbnail eyedropper, and then click an appropriate area in the Composition window or the original image thumbnail.
• Select the Key Color eyedropper, and then click an appropriate area in the Composition or Layer window.
• To preview transparency for different colors, select the Key Color eyedropper, hold down the Alt key (Windows) or Option key (Mac OS), and move the cursor to different areas in the Composition window or the original image thumbnail. The transparency of the image in the Composition window changes as you move the cursor over different colors or shades. Click to select the color.
• Click the Key Color swatch to select a color from the specified color space. The selected color becomes transparent.

Note: The eyedropper tools move the sliders accordingly. Use the sliders in steps 6 and 7 to fine-tune the keying results.

6. Adjust matching tolerance in one of the following ways:
• Select the Plus (+) or the Minus (-) eyedropper, and then click a color in the left thumbnail. The Plus eyedropper adds the specified color to the key color range, increasing the matching tolerance and the level of transparency. The Minus eyedropper subtracts the specified color from the key color range, decreasing the matching tolerance and the level of transparency.
• Drag the matching tolerance slider. A value of 0 makes the entire image opaque; a value of 100 makes the entire image transparent.
7. Drag the Matching Softness slider bar to soften the matching tolerance by tapering the tolerance value. Typically, values under 20% produce the best results.
8. Before closing the Effect Controls window, make sure that you have selected Final Output from the View menu to ensure that After Effects renders the transparency.

To preserve a color after applying the Linear Color Key:

1. In the Effect Controls or Timeline window, turn off any current instances of keys or matte tools by deselecting the Effect option to the left of the key name or tool name. This displays the original image in the Composition window so that you can select a color to preserve.
2. Choose Effect > Keying > Linear Color Key. A second set of Linear Color Key controls appears in the Effect Controls window below the first set.
3. In the Effect Controls window, choose Keep Colors from the Key Operation menu.
4. Select the color you want to keep.
5. In the first application of the Linear Color Key, choose Final Output from the View menu in the Effect Controls window, and then turn other instances of the Linear Color Key back on to examine the transparency. You may need to adjust colors or reapply the key a third time to find the results you need.