The Art and Science of Green Screen Keying, Part 2

Taught by Victor Perez

Course Number:
Software Version:
Original Run Date:
November 2016 
6 hours 17 minutes 
Pulling a key from a greenscreen is one of the basic skills for any compositor but only the most skilled artists can create the illusion of the integration of an extracted green screen element with other CG layers to make it look like it was shot at the same time, with the same camera and lenses under the same lights. For a compositor there is more to see than just green pixels and an alpha channel. The elaboration of a green screen or blue screen requires both fine artistic eye and a methodological mindset.

Professor Victor Perez has designed this two-part course to teach you all the available keying tools in Nuke X and how to use them to pull a key as a real pro. In part two of the course, Victor builds upon the theories learned in Part 1 and dives into using the tools and showing techniques on how to get great keys in Nuke X. 'The Art and Science of Green Screen Keying, Part 2' contains over five hours of instruction as well as footage files (available with our premium membership).

Topics covered in this course:

Spill and Color
• Despill Algorithms and Expressions
• Despill within Keyers: Keylight
• Hue Correction and Suppression
• Restoration of Screen Luminance
• Restoration of Background-Relative Luminance

Non-Alpha Advanced Keyers
• High Frequency Pass
• Additive Keyer
• Multiplicative Keyer
• VKeyer®

Post-Processing Mattes Operations
• Dilate/Erode Filtes
• Median Matrix
• Blur and Grade Combo

Compositing the Greenscreen Element and Its Qualities of Light
• The ‘Beauty’ Matte (Perfect Pixel Accurate Key)
• Light Qualities vs Edge Density
• The Motion Blur Issue
• Background-Relative Luminance Against Semitransparent Areas
• Physics of Radiation Of Light Against Edge Surfaces
• Bloom and Glare
• Reflections and Non-Alpha Greenscreen Areas Fusion Methodology
• Edge Blend
• Grain Restoration
• Color Grading: Who is the Reference

Victor Perez is a senior visual effects artist with over 12 years of production experience in computer graphics, digital grading and visual effects, as well as a NUKE Official Certified Trainer by The Foundry. As a senior digital compositing artist and 2D Technical Director he has a fine combination of both artistic and technical understanding of film post-production and visual effects. Member of Visual Effects Society and usual collaborator of Nukepedia. Victor has worked and researched with Oscar winner studios such as Cinesite and Double Negative and others. His personal web site is
The Art and Science of Green Screen Keying, Part 2
Watch our overview of the course

Class Listing

Class 1

Introduction. A broad overview of all the subjects discussed in this course. A personal methodology.

Class 2

Setting up a greenscreen comp script layout. The Alpha processing. Order and operations for the Auxiliary Mattes: Manual Garbage & Holdout

Class 3

The Boolean Logic fundamentals (“Frankesteining”), Mixing and Postprocessing Keys. Edge Fine Tune. The Median Matrix.

Class 4

Adding Rotoscoping to areas not covered by the greenscreen vs. reconstructing the greenscreen (preparing a greenscreen). Reconstructing soft edges.

Class 5

Procedural Garbage Matte and Procedural Holdout Matte. The Edge Matte. Manual “Clip Rollback”.

Class 6

The RGB Process, The Problem of Despill on semitransparencies vs. Spill Light on Opaque areas. Skintone corrections. Spill Suppression. Spill Map, Spill-Suppressed Plate Relight, Dynamic Despill-Relight Restoration Based on Background Luminance Map. Spill Holdout and the Problem of Despilled Grain. Recolour Greenscreen Elements

Class 7

Different Types of Despill: Keylight Alpha-Bias, Hue Correct: Suppressors, Selective Hue Amount and Selective Hue Saturation Control. 3D Visualisation of Spill Corrections. Fine-Tuning the Despill Map. Greenscreen Adjacent Hue Operations: Handling Hue Corrections Curves for Screen Suppression and Color Restoration.

Class 8

Non-Additive Keyers I: The Additive Key Fundamentals, The Minus/Plus Combo & the Divide/Multiply Combo. The Motion Blur Recovery Fundamentals, Painting with light principles. Improvements to the basics of the Additive Setup. Additive Detail Color Restoration.

Class 9

Non-Additive Keyers II: High Frequency Filter Extraction. Image Based High Frequency Demystified. Extracting Areas in Focus against Out-Of-Focus Backgrounds: Drops over Window Glass Background Replacement. The Additive Key on Non-Greenscreen Case Scenarios.

Class 10

The VKeyer® Setup: Dynamic Critical Light Environment Procedural Restoration. Recovering Specularity, Frostiness. Refining Refraction and Semitransparency. The Loose Key mix with The Beauty Key. Recovering Shadows.

Class 11

Light Diffusion Fundamentals. Light Radiance Behaviour Study. Backlight, selective Lightwrapping: Diffussion and Intensity Fundamentals. Environment Light Conditions: Recreating The Light Conditions From Behind the Camera. Atmospheric Occlusion: Size vs. Color, Qualities of Air to Consider About Color and Diffusion. Light Bleeding, Bloom, Glare, Flare. Light Contrast Aspect Ratio. Backlight Environmental Influence. Edge Blending Recommendations.