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Keying effects


 

After Effects includes several built-in keying effects, as well as the Academy Award–winning Keylight effect, which excels at professional-quality color keying. For information on the Keylight effect, see its documentation in the folder in which the Keylight plug-in is installed. (See Plug-ins.)

Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects—such as the Color Key effect—have been superseded by more modern effects like Keylight.

For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

Third-party effects in this category included with After Effects:

  • Keylight effect

  • CC Simple Wire Removal effect

See Third-party plug-ins included with After Effects.

    Color Difference Key effect

    Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern effects like Keylight.

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    The Color Difference Key effect creates transparency from opposite starting points by dividing an image into two mattes, Matte Partial A and Matte Partial B. Matte Partial B bases the transparency on the specified key color, and Matte Partial A bases transparency on areas of the image that don’t contain a second, different color. By combining the two mattes into a third matte, called the alpha matte, the Color Difference Key creates well-defined transparency values.

    The Color Difference Key produces high-quality keying for all well-lit footage items shot against a bluescreen or greenscreen and works especially well with images that contain transparent or semitransparent areas, such as smoke, shadows, or glass.

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

    Use the Color Difference Key effect

    1. Select the layer that you want to make partially transparent, and choose Effect > Keying > Color Difference Key.
      Note: To use any of the eyedroppers in the Layer panel, choose Color Difference Key from the View menu in the Layer panel.
    2. In the Effect Controls panel, choose Matte Corrected from the View menu. To view and compare the source image, both partial mattes, and the final matte at the same time, choose [A, B, Matte] Corrected, Final from the View menu. Other views available in the View menu are described in step 10.
    3. Select the appropriate key color: To key out a bluescreen, use the default blue color. To key out a nonblue screen, select a key color in one of the following ways:

      • Thumbnail eyedropper: Select and then click in the Composition panel or the original thumbnail image on an appropriate area.

      • Key Color eyedropper: Select and then click in the Composition or Layer panel on an appropriate area.

      • Key Color swatch: Click to select a color from the specified color space.

        Note: The eyedropper tools move the sliders accordingly. Use the sliders in step 9 to fine-tune the keying results.
    4. Click the matte button to display the final combined matte in the matte thumbnail.
    5. Select the Black eyedropper, and then click inside the matte thumbnail on the lightest area of black to specify transparent regions. The transparency values in the thumbnail and Composition panel are adjusted.
    6. Select the White eyedropper, and then click inside the matte thumbnail on the darkest area of white to specify opaque regions. The opaque values in the thumbnail and the Composition panel are adjusted.
      To produce the best possible key, make the black and white areas as different as you can so that the image retains as many shades of gray as possible.
    7. Select a matching accuracy from the Color Matching Accuracy menu. Choose Faster unless you use a screen that isn’t a primary color (red, blue, or yellow). For those screens, choose More Accurate, which increases rendering time but produces better results.
    8. To further adjust transparency values, repeat steps 5 and 6 for one or both of the partial mattes. Click the Partial Matte B button or the Partial Matte A button to select a partial matte, and then repeat the steps.
    9. Adjust transparency values for each partial matte and for the final matte by dragging one or more of the following sliders in the Matte Controls section:

      • Black sliders adjust the transparency levels of each matte. You can adjust the same levels using the Black eyedropper.

      • White sliders adjust the opaque levels of each matte. You can adjust the same levels using the White eyedropper.

      • Gamma sliders control how closely the transparency values follow a linear progression. At a value of 1 (the default), the progression is linear. Other values produce nonlinear progressions for particular adjustments or visual effects.

    10. When adjusting individual mattes, choose from the View menu to compare the mattes with and without adjustments:

      • Choose Uncorrected to view a matte without adjustments.

      • Choose Corrected to view a matte with all adjustments.

    11. Before closing the Effect Controls panel, select Final Output from the View menu. Final Output must be selected for After Effects to render the transparency.
      To remove traces of reflected key color from the image, apply Spill Suppressor using Better For Color Accuracy. If the image still has a lot of color, apply the Simple Choker or Matte Choker effect.

    Color Key effect

    Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern effects like Keylight.

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    The Color Key effect keys out all image pixels that are similar to a specified key color. This effect modifies only the alpha channel of a layer.

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

    Key out a single color with the Color Key effect

    1. Select the layer that you want to make partially transparent, and choose Effect > Keying > Color Key.
    2. In the Effect Controls panel, specify a key color in one of two ways:

      • Click the Key Color swatch to open the Color dialog box and specify a color.

      • Click the eyedropper, and then click a color on the screen.

    3. Drag the Color Tolerance slider to specify the range of color to key out. Lower values key out a smaller range of colors near the key color. Higher values key out a wider range of color.
    4. Drag the Edge Thin slider to adjust the width of the border of the keyed area. Positive values enlarge the mask, increasing the transparent area. Negative values shrink the mask, decreasing the transparent area.
    5. Drag the Edge Feather slider to specify the softness of the edge. Higher values create a softer edge but take longer to render.

    Color Range effect

    Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern effects like Keylight.

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    The Color Range effect creates transparency by keying out a specified range of colors in either the Lab, YUV, or RGB color space. You can use this key on screens that consist of more than one color or on bluescreens or greenscreens that have been unevenly lit and contain different shades of the same color.

    This effect works with 8-bpc color.

    Poorly lit greenscreen (upper-left) and background layer (lower-left) are combined using Color Range Key (lower-right).

    Use the Color Range effect

    1. Select the layer that you want to make partially transparent, and choose Effect > Keying > Color Range.
    2. Choose Lab, YUV, or RGB from the Color Space menu. If you have trouble isolating the subject using one color space, try using a different one.
    3. Select the Key Color eyedropper, and then click in the matte thumbnail to select the area that corresponds to a color in the Composition panel you want to make transparent. Typically, this first color is the one that covers the largest area of the image.
      Note: To use the eyedroppers in the Layer panel, choose Color Range from the View menu in the Layer panel.
    4. Select the plus eyedropper, and then click other areas in the matte thumbnail to add other colors or shades to the range of colors keyed out for transparency.
    5. Select the minus eyedropper, and then click areas in the matte thumbnail to subtract other colors or shades from the range of colors keyed out.
    6. Drag the Fuzziness slider to soften the edges between transparent and opaque regions.
    7. Use the sliders in the Min and Max controls to fine-tune the color range you selected with the plus and minus eyedroppers. The L, Y, R sliders control the first component of the specified color space; the a, U, G sliders control the second component; and the b, V, B sliders control the third component. Drag the Min sliders to fine-tune the beginning of the color range. Drag the Max sliders to fine-tune the end of the color range.

    Difference Matte effect

    The Difference Matte effect creates transparency by comparing a source layer with a difference layer, and then keying out pixels in the source layer that match both the position and color in the difference layer. Typically, it’s used to key out a static background behind a moving object, which is then placed on a different background. Often the difference layer is simply a frame of background footage (before the moving object has entered the scene). For this reason, the Difference Matte effect is best used for scenes that have been shot with a stationary camera and an unmoving background.

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

    Difference Matte Key effect
    A.
    Original image

    B.
    Background image

    C.
    New background image

    D.
    Final composite image

    Use the Difference Matte effect

    1. Select a motion footage layer as the source layer.
    2. In the source layer, find a frame that consists only of background, and save the background frame as an image file. (See Render and export a single frame of a composition.)
    3. Import the image file into After Effects, and add it to the composition.

      The imported image becomes the difference layer. Make sure that its duration is at least as long as the duration of the source layer.

      Note: If the shot doesn’t contain a full background frame, you may be able to assemble the full background by combining parts of several frames in After Effects or Photoshop. For example, you can use the Clone Stamp tool to take a sample of the background in one frame, and then paint the sample over part of the background in another frame.
    4. Turn off the display of the difference layer by clicking the Video switch in the Timeline panel.
    5. Make sure that the original source layer is selected, and then choose Effect > Keying > Difference Matte.
    6. In the Effect Controls panel, choose Final Output or Matte Only from the View menu. (Use the Matte Only view to check for holes in the transparency. To fill undesired holes after you complete the keying process, see Close a hole in a matte.)
    7. Select the background file from the Difference Layer menu.
    8. If the difference layer isn’t the same size as the source layer, choose one of the following controls from the If Layer Sizes Differ menu:
      Center
      Places the difference layer in the center of the source layer. If the difference layer is smaller than the source layer, the rest of the layer fills with black.

      Stretch To Fit
      Stretches or shrinks the difference layer to the size of the source layer. Background images may become distorted.

    9. Adjust the Matching Tolerance slider to specify the amount of transparency based on how closely colors must match between the layers. Lower values produce less transparency; higher values produce more transparency.
    10. Adjust the Matching Softness slider to soften the edges between transparent and opaque areas. Higher values make matched pixels more transparent but don’t increase the number of matching pixels.
    11. If the matte still contains extraneous pixels, adjust the Blur Before Difference slider. This slider suppresses noise by slightly blurring both layers before the comparison is made.
      Note: The blurring occurs only for the comparison and doesn’t blur final output.
    12. Before closing the Effect Controls panel, make sure to select Final Output from the View menu to ensure that After Effects renders the transparency.

    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 dark or bright but consists of more than one color.

    Note: The controls for this effect are similar to the controls 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 partially transparent, and 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, first shorten the transparency bar.

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

    Inner/Outer Key effect

    Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern effects like Keylight.

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    The Inner/Outer Key effect isolates a foreground object from its background.

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

    Use the Inner/Outer Key effect

    To use the Inner/Outer key, create a mask to define the inside and outside edge of the object you want to isolate. The mask can be fairly rough—it doesn’t need to fit exactly around the edges of the object.

    In addition to masking a soft-edged object from its background, Inner/Outer Key modifies the colors around the border to remove contaminating background colors. This color decontamination process determines the contribution of the background to the color in each border pixel, and then removes that contribution—thus removing the halo that can appear if a soft-edged object is matted against a new background.

    1. Select the border of the object that you want to extract by doing one of the following:

      • Draw a single closed mask near the border of the object; then select the mask from the Foreground menu and leave the Background menu set to None. Adjust the Single Mask Highlight Radius to control the size of the border around this mask. (This method works well only on objects with simple edges.)

      • Draw two closed masks: an inner mask just inside the object, and an outer mask just outside the object. Make sure that any fuzzy or uncertain areas of the object lie within these two masks. Select the inner mask from the Foreground menu and the outer mask from the Background menu.

        Note: Make sure that the mask mode for all masks is set to None.
    2. If you want, move the masks around to find the location that provides the best results.
    3. To extract more than one object, or to create a hole in an object, draw additional masks and then select them from the Additional Foreground and Additional Background menus. For example, to key out a person’s hair blowing in the wind against a blue sky, draw the inner mask inside the head, draw the outer mask around the outside edge of the hair, and then draw an additional mask around the gap in the hair where you can see sky. Select the additional mask from the Additional Foreground menu to extract the gap and remove the background image.
    4. Create additional open or closed masks to clean up other areas of the image, and then select them from the Cleanup Foreground or Cleanup Background menu. Cleanup Foreground masks increase the opacity along the mask; Cleanup Background masks decrease the opacity along the mask. Use the Brush Radius and Brush Pressure options to control the size and density of each stroke.
      Note: You can select the Background (outer) mask as a Cleanup Background mask to clean up noise from the background portions of the image.
    5. Set Edge Thin to specify how much of the border of the matte is affected by the key. A positive value moves the edge away from the transparent region, increasing the transparent area; a negative value moves the edge toward the transparent region and increases the size of the foreground area.
    6. Increase the Edge Feather values to soften edges of the keyed area. High Edge Feather values take longer to render.
    7. Specify the Edge Threshold, which is a soft cutoff for removing low-opacity pixels that can cause unwanted noise in the image background.
    8. Select Invert Extraction to reverse the foreground and background regions.
    9. Set Blend With Original to specify the degree to which the resulting extracted image blends with the original image.

    Linear Color Key effect

    Note: Though the color keying effects built into After Effects can be useful for some purposes, you should try keying with Keylight before attempting to use these built-in keying effects. Some keying effects have been superseded by more modern effects like Keylight.

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    Linear keys create a range of transparency across an image. A linear key compares each pixel in the image to the key color you specify. If the color of a pixel closely matches the key color, it becomes completely transparent. Pixels that don’t match as well are made less transparent, and pixels that don’t match at all remain opaque. The range of transparency values, therefore, forms a linear progression.

    The Linear Color Key effect uses RGB, hue, or chroma information to create transparency from a specified key color.

    This effect works with 8-bpc, 16-bpc, and 32-bpc color.

    Apply the Linear Color Key effect

    In the Effect Controls panel, the Linear Color Key effect displays two thumbnail images; the left thumbnail image represents the unaltered source image, and the right thumbnail image represents the view you’ve selected in the View menu.

    You can adjust the key color, the matching tolerance, and the matching softness. The matching tolerance specifies how closely pixels must match the key color before they start becoming transparent. The matching softness controls the softness of edges between the image and the key color.

    You can also reapply this key to preserve a color that was made transparent by the first application of the key. For example, if you key out a medium-blue screen, you may lose some or all of a light-blue piece of clothing your subject is wearing. You can bring back the light-blue color by applying another instance of the Linear Color Key and choosing Keep This Color from the Key Operation menu.

    1. Select a layer as the source layer, and then choose Effect > Keying > Linear Color Key.
    2. In the Effect Controls panel, 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 have trouble isolating the subject using one color space, try using a different color space.
    4. In the Effect Controls panel, choose Final Output from the View menu. The view you choose appears in the right thumbnail and in the Composition panel. 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 Close a hole in a matte.

    5. Select a key color in one of the following ways:

      • Select the Thumbnail eyedropper, and then click an appropriate area in the Composition panel or the original thumbnail image.

      • Select the Key Color eyedropper, and then click an appropriate area in the Composition or Layer panel.

      • 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 pointer to different areas in the Composition panel or the original thumbnail image. The transparency of the image in the Composition panel changes as you move the pointer 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. To use eyedroppers in the Layer panel, choose Linear Color Key from the View menu in the Layer panel.
    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 image. 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 to soften the matching tolerance by tapering the tolerance value. Typically, values under 20% produce the best results.
    8. Before closing the Effect Controls panel, make sure to select Final Output from the View menu to ensure that After Effects renders the transparency.

    Preserve a color after applying Linear Color Key

    1. In the Effect Controls panel or Timeline panel, turn off any current instances of keys or matte effects by deselecting the Effect option to the left of the key name or tool name. Deselecting the option causes the original image to appear in the Composition panel 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 panel below the first set.
    3. In the Effect Controls panel, 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 effect, choose Final Output from the View menu in the Effect Controls panel, and then turn other instances of the Linear Color Key effect back on to examine the transparency. You may need to adjust colors or reapply the key a third time to get the results you need.

    Luma Key effect

    For information about keying in general, including links to tutorials and other resources, see Keying introduction and resources.

    The Luma Key effect keys out all the regions of a layer with a specified luminance or brightness. The quality setting of the layer doesn’t influence the Luma Key effect.

    Use this effect if the object from which you want to create a matte has a greatly different luminance value than its background. For example, if you want to create a matte for musical notes on a white background, you can key out the brighter values; the dark musical notes become the only opaque areas.

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

    White background of original (upper-left and lower-left) is removed using Luma Key and composited over underlying layer (lower-right).

    Key out a luminance value with the Luma Key effect

    1. Select the layer that you want to make partially transparent, and choose Effect > Keying > Luma Key.
    2. Select a Key Type to specify the range to be keyed out.
    3. Drag the Threshold slider in the Effect Controls panel to set the luminance value you want the matte to be based on.
    4. Drag the Tolerance slider to specify the range of values to be keyed out. Lower values key out a smaller range of values near the threshold. Higher values key out a wider range of values.
    5. Drag the Edge Thin slider to adjust the width of the border of the keyed area. Positive values make the mask grow, increasing the transparent area. Negative values shrink the mask.
    6. Drag the Edge Feather slider to specify the softness of the edge. Higher values create a softer edge but take longer to render.

    Spill Suppressor effect

    The Spill Suppressor effect removes traces of the key color from an image with a screen that’s already been keyed out. Typically, the Spill Suppressor is used to remove key color spills from the edges of an image. Spills are caused by light reflecting off the screen and onto the subject.

    If you’re not satisfied with the results from using the Spill Suppressor, try applying the Hue/Saturation effect to a layer after keying, and then decrease the saturation value to de-emphasize the key color. (See Hue/Saturation effect.)

    This effect works with 8-bpc and 16-bpc color. In After Effects CS6 or later, this effect works in 32-bit color.

    Original greenscreen (upper-left) leaves green glow when keyed out (lower-left). Spill Suppressor removes glow (lower-right).

    Use the Spill Suppressor effect

    1. Select the layer, and choose Effect > Keying > Spill Suppressor.
    2. Choose the color you want to suppress in one of the following ways:

      • If you already keyed out the color with a key in the Effect Controls panel, click the Color To Suppress eyedropper, and then click the screen color in the Key Color swatch for the key.

      • In Spill Suppressor, click the Key Color swatch and choose a color from the color wheel.

      Note: To use the eyedropper in the Layer panel, choose Spill Suppressor from the View menu in the Layer panel.
    3. From the Color Accuracy menu, choose Faster to suppress blue, green, or red. Choose Better to suppress other colors, because After Effects may need to analyze the colors more carefully to produce accurate transparency. The Better option may increase rendering time.
    4. Drag the Suppression slider until the color is adequately suppressed.
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