Luma Keyer Node

The Luma Keyer is an all-purpose channel keyer that works on a scalar value (usually the luminance, but you can point it to any channel). Each pixel is tested against a brightness threshold → opaque or transparent accordingly.

Typical use: when your subject and your background have distinct brightness levels (white text on black, a bright subject in front of a deep shadow, a very bright sky…), the Luma Keyer separates them cleanly without caring about color.

• Effects Library: Tools > Matte > Luma Keyer
• Quick add: right-click in the Node Editor → Add Tool > Matte > Luma Keyer

• Input (orange) - required. The 2D image to key.
• Garbage Matte (gray) - optional. Areas forced to transparent.
• Solid Matte (white) - optional. Areas forced to opaque.
• Effect Mask (blue) - optional. Limits the keying to an area.

MediaIn (plate) → Luma Keyer → Merge 2D → Saver

Threshold Range

A double slider:

• Pixels with a luminance below the low threshold → transparent.
• Pixels with a luminance above the high threshold → opaque.
• In between → a grayscale gradation for a smooth transition.

Filter

4 filtering algorithms:

• Box - the fastest, low quality.
• Bartlett - balanced.
• Multi-box - a compromise, with adjustable passes.
• Gaussian - best quality, possible artifacts on the edges.

Blur

Softens the edges of the matte.

Contract / Expand

Shrinks or grows the semi-transparent areas.

Gamma

Adjusts the opacity in the gray areas of the matte (without touching pure black and pure white).

Invert

Inverts the transparency (opaque ↔ transparent areas). Lets you switch from "keep the brights" to "keep the darks" in one click.

Post-Multiply Image

Multiplies the RGB channels by the generated alpha. A premultiplied output ready for compositing.

Luma Keyer (this node)

Based on luminance. Simple, fast. Perfect when the separation between subject and background is a matter of brightness, not hue.

Chroma / Delta / Ultra Keyer

Based on color. Needed for green/ blue screen or isolating by hue.

Difference Keyer

Based on the difference with a clean plate. For locked-off cameras without an even backdrop.

Rule: reach for the Luma Keyer whenever your image is naturally high-contrast (text on a plain background, a bright object on a dark background, sky vs landscape).

• Extracting a sky or clouds - the sky is usually much brighter than the landscape. A high Threshold → isolates the sky easily, with no color keying needed.
• White text on a dark background (or the reverse) - credits, a logo, a white title → a Luma Keyer with a high threshold cleanly isolates the text.
• Highlights only - extract the brightest areas to apply a dedicated glow to them (Threshold 0.9+). A color grading classic.
• Shadows only - same idea but with Invert ticked and a low threshold. Useful to tint the shadows specifically.
• Lightning bolt - in a night shot, the lightning is extremely bright compared with the background. The Luma Keyer isolates it cleanly.
• A mask from an isolated channel - combine with Channel Booleans (to isolate the green channel, for example) + Luma Keyer = an extraction based on a specific channel.
• Pre-matte for a color keyer - use the Luma Keyer to roughly identify the areas, then refine with a Delta Keyer.

• Invert = game changer - one tick takes you from "brights" to "darks". Don't forget it.
• Narrow Threshold + Blur for sharp edges with a bit of softness. Avoids the "paper cutout" look.
• Convert to black and white first? - if the image has colors, keep in mind that the Luma Keyer computes a weighted luminance (not a simple RGB average). For more controlled results, convert to black and white explicitly first (with Color Space in BW mode with custom sliders).
• Contract + Blur = the finishing combo - used on almost every key to soften the edges without losing area.
• For animated text, the Luma Keyer is cleaner than a Chroma Keyer even if the text is colored - the tonal difference between text and background is usually more reliable than the color difference.
• Post-Multiply for compositing - turn it on if the result goes straight into a Merge 2D. Otherwise the semi-transparent edges will look wrong.