AfterEffects

Extract effect

The Extract effect creates transparency by keying out a specified brightness range, based on a histogram of a specified channel. It’s best used to create transparency in an image shot against a black or white background or against a background that is very dark or bright but consists of more than one color.

Note: The controls for this effect are similar to those of the Extract effect in Adobe Premiere Pro, but the purpose and results of the effect are different.

This effect works with 8-bpc and 16-bpc color.

Use the Extract effect

In the Effect Controls panel, the Extract effect displays a histogram for a channel specified in the Channel menu. The histogram displays a representation of the brightness levels in the layer, showing the relative number of pixels at each level. From left to right, the histogram extends from the darkest (a value of 0) to the lightest (a value of 255).

Using the transparency control bar beneath the histogram, you can adjust the range of pixels that are made transparent. The position and shape of the bar in relation to the histogram determine transparency. Pixels corresponding to the area covered by the bar remain opaque; pixels corresponding to the areas not covered by the bar are made transparent.

  1. Select the layer you want to make transparent, and then choose Effect > Keying > Extract.
  2. If you are keying out bright or dark areas, choose Luminance from the Channel menu. To create visual effects, choose Red, Green, Blue, or Alpha.
  3. Adjust the amount of transparency by dragging the transparency control bar in the following ways:

    • Drag the upper right or upper left selection handles to adjust the length of the bar and to shorten or lengthen the transparency range. You can also adjust the length by moving the White Point and Black Point sliders. Values above the white point and below the black point are made transparent.

    • Drag the lower right or lower left selection handles to taper the bar. Tapering the bar on the left affects the softness of transparency in the darker areas of the image; tapering it on the right affects the softness in the lighter areas. You can also adjust the softness levels by adjusting White Softness (lighter areas) and Black Softness (darker areas).

      Note: To taper the edges of the transparency control bar, you must first shorten the transparency bar.

    • Drag the entire bar left or right to position it under the histogram.