Select the layer, and choose Effect
> Matte > Matte Choker.
Last updated on
Jun 27, 2025
Note
- For information on the Refine Matte effect and the Roto Brush effect, refer to Roto Brush effect and Refine Matte effect reference.
- Learn more about third-party plug-ins included with After Effects.
Matte Choker effect
The Matte Choker effect repeats a sequence of choking and spreading the matte to fill undesired holes (transparent areas) in opaque regions. The repetition is necessary because the entire matte must be choked and spread; the spreading fills the hole, but the edges of the matte must be choked back to preserve the matte shape.
The process of choking and spreading occurs in two stages, each with its own set of identical controls. Typically, stage two does the opposite of stage one. After a specified number of back-and-forth adjustments (which Matte Choker handles automatically), the hole is filled.
This effect works with 8-bpc and 16-bpc color.
Note
You can use the Matte Choker effect to only blur the alpha channel. To use this effect as an alpha-channel blur, set Gray Level Softness to 100%.
Close a hole in a matte
Set stage-one controls (the first three properties) to
spread the matte as far as possible without altering its shape,
as follows:
Geometric Softness
Specifies (in pixels) the largest spread or choke.
Choke
Sets the amount of choke. Negative values spread the matte; positive values choke it.
Gray Level Softness
Specifies how soft to make the edges of the matte. At 0%, the matte edges contain only fully opaque and fully transparent values. At 100%, the matte edges have a full range of gray values but may appear blurred.
Set stage-two controls (the next three properties) to
choke the matte by the same amount as the amount by which you spread
it in stage one.
(Optional) Use the Iterations property to specify how
many times After Effects repeats the spread-and-choke sequence.
You may need to try a few different settings so that the sequence
is repeated as many times as necessary to close any unwanted holes.
The Refine Soft Matte effect allows you to fine-tune mattes, especially when dealing with keyed footage (like green screen), where edge quality is crucial. It's commonly applied after keying effects like Keylight to enhance the edges of the matte and eliminate unwanted edge artifacts like color spill or noise.
Calculate Edge Details
Enable automatic detection of soft edges. This helps preserve motion blur or hair details in the matte.
Additional Edge Radius
Determine how far beyond the original edge the software analyzes. Higher values expand the area being refined, helping to capture finer edge motion or hair details.
View Edge Region
Enable it to show the area being analyzed and refined.
Smooth
Soften the edges of the matte to reduce jaggedness.
Feather
Blur the edge of the matte, creating a more natural blend with the background.
Contrast
Increase the edge contrast, making the matte edge harder or more defined.
Shift Edge
Move the edge inward or outward. Positive values expand the matte, negative values contract it.
Chatter Reduction
Reduces noise in the matte edge over time. This is helpful when the matte flickers frame to frame.
More Motion Blur
Enable it to enhance motion blur around soft edges. It is useful for fast-moving subjects.
Decontaminate Edge Colors
Remove background color fringing from the edges of the matte. It is helpful in green or blue screen work where spills can affect hair or transparent areas.
Decontamination
Adjust the following settings to fine-tune the edge color decontamination:
- Amount: Control how strongly the edge colors are replaced with nearby foreground colors.
- Extend Where Smoothed: Extend the decontamination into smoothed areas.
- Increase Radius: Expand the area for decontamination beyond the immediate edge, capturing more spill if needed.
- View Map: Display the decontamination map visually, helping you see what’s being adjusted.
The Simple Choker effect shrinks or expands the edges of a matte in small increments to create a cleaner matte. The Final Output view displays the image with the effect applied, and the Matte view provides a black-and-white view of the image with black areas indicating transparency and white areas indicating opacity. Choke Matte sets the amount of choke. Negative values spread the matte; positive values choke it.
This effect works with 8-bpc, 16-bpc, and 32-bpc color.
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