Chroma Key removes a backdrop and makes what is left the layer’s real shape. It is not a green-screen effect with a colour picker bolted on: it keys a screen of any colour — green, blue, red, magenta, white, black or a mid grey — and picks the right keying maths for the colour you gave it.
It is a Layer Effect, free rather than PRO, and it works on video, image, sequence and grid layers.
Add it
Select the layer, open LAYER EFFECTS, and add Chroma Key from the Keying pack. When the effect is added the editor samples the footage and sets Screen Colour to the dominant colour cluster it finds — which is usually right, and always the first thing to check if the key is doing nothing.
Screen Colour must match the footage. A generic green keys nothing on a blue or white plate. Use the eyedropper on a patch of screen away from the subject.
It runs first
Chroma Key runs before every other per-layer stage, in place on the isolated plate. Everything after it sees the keyed silhouette rather than the original rectangle:
- a Layer Mask cuts the keyed shape,
- Running Glow traces the subject’s outline instead of the frame edge,
- camera depth of field gathers against the real silhouette,
- Motion Blur and Motion Trail smear the keyed look,
- a Track Matte still gets the last word.
That ordering is the reason it is a layer effect rather than an entry in the Overlay Effects chain.
Method
Method ▸ Auto picks the keyer from the screen colour, and it is the right choice almost always:
| Screen | Keyer it picks | Why |
|---|---|---|
| Saturated (green, blue, red, magenta, yellow…) | Colour Difference | The Keylight family. The key hue is rotated onto green internally, so a blue, red or magenta screen keys exactly like a green one, and an unevenly lit cloth keys from one pair of clip levels. |
| Very light or very dark (white, black) | Luma | There is no hue to difference against, so brightness is what separates subject from backdrop. |
| Mid grey | 3D Colour Distance | Neither hue nor brightness alone separates it; distance in colour space does. |
You can force any of the four — Colour Difference, Chroma Distance, Luma or 3D — when Auto guesses wrong.
Tuning the key
Colour Difference
- Balance compares the key channel against the stronger or the weaker of the other two. Lower it to about 35 when a dark subject or dark skin goes semi-transparent on a yellow-green screen — that is the single most useful control here.
- Adapt scales the expected screen level by each pixel’s brightness, so a dark corner of the screen still reads as screen. Raise it toward 80 for a badly lit cyclorama.
The distance keyers use Tolerance instead, with Luma Weight (3D) or Chroma Guard (Luma).
Matte levels
These apply whichever keyer is running, and they are where most keys are actually won:
- Gain multiplies screen-ness — raise it to clear noise on the screen.
- Clip Black raises the floor: push it up to clean the screen to solid transparency.
- Clip White lowers the ceiling: pull it down to make the subject fully opaque.
- Choke erodes (negative) or grows (positive) the matte, in composition pixels. A grown matte reveals the source pixel rather than a black fringe, and never past the layer box.
- Feather softens the matte edge, also in composition pixels.
Spill
Screen light lands on edges and hair, and Spill clamps that hue out of the subject. Spill Bias picks how much of the other channels’ envelope survives, Spill Luma puts the removed brightness back as grey, and Spill Tint replaces it with a colour instead. Spill is switched off automatically for a hue-less key — white, black or grey — because there is no hue to remove.
Light wrap
Light Wrap tints the matte’s edge with a colour, which is how a keyed subject stops looking pasted on. Set the colour to whatever will sit behind the layer, with Width in pixels. It is a colour rather than the scene itself: a layer effect cannot see the layers below it.
Views and amount
View renders into the output — Matte shows the key in greys, Status shows a black / grey / white breakdown of what is solid, soft and gone. Both export exactly as shown, so leave the view on Result in any project meant for delivery.
Amount mixes back toward the unkeyed plate; 0 is an exact bypass. Every number except the screen colour and the two selects keyframes.
Starting points
These measured best against ground-truth mattes in testing, all with the screen colour sampled from the plate first:
| Footage | Start from |
|---|---|
| Coloured screen, fine hair | Gain 100, Clip Black 10, Clip White 85 |
| Dark subject on a yellow-green screen | Balance 35, Clip White 62 |
| Compressed or webcam footage | Clip Black 14, Clip White 80, Choke −0.6, Feather 1.2 |
| Unevenly lit cyclorama | Adapt 80, Gain 135, Clip Black 12 |
| White backdrop | Method 3D, Tolerance 0.38, Chroma Guard 3, Gain 120, Clip Black 14, Clip White 85, Spill 0 |
| Black backdrop | Method 3D, Tolerance 0.2, Chroma Guard 2, Gain 130, Clip Black 8, Clip White 80, Spill 0 |
| Grey backdrop | Method 3D Colour Distance, Tolerance 0.34, Luma Weight 1.4, Gain 130, Clip Black 8, Clip White 70, Spill 0 |
The panel also ships presets along those lines — Clean Screen, Fine Hair, Dark Subject, Compressed Footage, Uneven Screen, and White / Black / Grey Backdrop.
Where to go next
- Layer Effects
- Track Matte — masking a layer by another layer’s alpha or brightness
- Overlay Effects — Extract keys on a level where this keys on a hue
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