---
title: "Keying"
url: https://postproduction.studio/en/glossary/keying
language: en
description: "Keying is the broader VFX practice of generating a matte (transparency mask) that isolates a foreground element from its background or context, enabling..."
updated: 2026-10-25
---

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# Keying

Keying is the broader VFX practice of generating a matte (transparency mask) that isolates a foreground element from its background or context, enabling clean compositing. Chroma key is one type of keying (based on color matching), but the family includes luma key (based on brightness, separating dark or bright elements), difference key (based on subtracting a clean background plate to find what was added), depth key (based on a 3D depth map from a depth camera or generated by AI), and IR key (used in modern multi-band cameras). Each method has its use cases: chroma for general background replacement, luma for fire, sparks, smoke against dark skies, difference for shots where a clean plate exists (controlled studio scenes), depth for stereoscopic work or when subjects wear similar colors to the background. The output of any keying operation is a matte — an alpha channel where white means opaque and black means transparent. Edges are the hard part: hair, motion blur, transparent fabric, glass, smoke, and any semi-transparent element requires careful edge work and often manual roto cleanup. Modern AI-based keyers (Runway, Foundry CopyCat, Adobe Sensei, DaVinci Magic Mask) increasingly handle subjects that don't require a colored background, identifying people and objects via machine learning. The keyed element is then color-corrected, edge-treated, despilled, and composited with the new background. Reference: VES Handbook of Visual Effects chapter on matte generation.

VFXCompositor, VFX ArtistVFX, Compositing

## Related terms

[Chroma Key](https://postproduction.studio/en/glossary/chroma-key)[Alpha Channel](https://postproduction.studio/en/glossary/alpha-channel)[Matte](https://postproduction.studio/en/glossary/matte)

Compositing combines multiple visual elements into a single final image. Each layer carries its own alpha matte and contributes to the final integration.

## Articles covering this term

* [Chroma subsampling and bit depth explained

  Understand the core concepts of 4:4:4, 4:2:2, and 4:2:0 chroma subsampling and bit depths in digital video workflows for post-production.](https://postproduction.studio/en/formats/chroma-subsampling)
* [VFX and compositing tools: Nuke, Fusion, AE, Houdini

  Deep dive into professional VFX and compositing tools. Explore node-based compositing, Nuke, DaVinci Resolve Fusion, After Effects, Houdini, and OFX integrations.](https://postproduction.studio/en/tools/vfx-and-compositing-tools)