Join Mark Christiansen for an in-depth discussion in this video Create a luma key with Extract, part of After Effects Compositing 04: Color Keying.
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- In this lesson we'll look at how to…create a matte using only luminance.…This is know as a luma key.…The result is what's called a high contrast…or hi-con matte,…which while generally cruder than a green screen…or blue screen color key…can certainly be an effective way…to separate foreground and background…when you need to and when you can get away with it.…Here is a scene which among other things…is just begging for a sky replacement…because this was an overcast day in Portland…and there's nothing going on up there.…
So to start I'll apply the extract effect.…It's among the keying effects…there used to be a luma key effect in after effects…happily it was obsoleted because it was pretty bad.…I thought that by moving my cursor around…I'd see the histogram and now I do.…I can extract the luminance channel but I also have…the option to choose one of the individual color channels.…I usually like to look at the three color channels…and decide which one has the best contrast.…So between red…green and blue…looking at the horizon line…
Beginning with a brief explanation of the keying process, Mark takes you through the steps involved in creating a perfect green-screen key: generating a rough matte, eliminating color spill and matte lines, and refining problematic edges. He shows how to work with Keylight and Primatte—two indispensable keying tools in After Effects—and explains when to use one over the other. And for times when green screen won't work, he shows how to generate high-contrast mattes, or luma keys, based on the luminance data in your footage. Last, learn about compression and how to prep a shot for keying.
- What is color keying?
- Using garbage mattes
- Getting started with Keylight
- Understanding the Screen Color, Clip Black, and Clip White adjustments
- Eliminating spill with Advanced Spill Suppressor
- Using Key Cleaner to refine edges automatically
- Dividing a matte with holdout mattes
- Breaking down a complex color key
- Creating a luma key with Extract
- Setting up sky replacement
- Using Refine Soft Matte to improve edge detail
- Feathering edges with Channel Blur
- Knowing when to avoid green screen
- Prepping a shot for keying
Skill Level Intermediate
After Effects Apprentice 12: Tracking and Keyingwith Chris Meyer3h 54m Intermediate
VFX Techniques: Crowd Replication with After Effectswith Lee Lanier2h 54m Intermediate
VFX Techniques: Tracking Objects onto a Facewith Lee Lanier2h 42m Intermediate
1. Work with Keylight
2. Manage Edges and Spill
3. Divide a Matte for Best Results When Keying
Add a holdout matte1m 38s
4. Solve Problematic Edges
5. Complex Color Keys and Primatte
6. High-Contrast Mattes (When There Is No Green Screen)
7. Prep for Success When Color Keying
Prep a shot for keying3m 4s
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