Ultimatte

You're in the edit suite, the greenscreen looks like a damp rag — unevenly lit, reflective, with spill everywhere. Your compositor attaches the first keying node and selects Ultimatte. Within seconds, the matte is in place. This isn't by chance, but decades of optimizing color difference mathematics that actually work.

Ultimatte operates on an elegant principle: It doesn't just measure if a color is "green," but analyzes the difference between color channels — specifically, the ratio of green to the other channels. A pixel with a real greenscreen has a characteristic profile: the G channel dominates massively, R and B are low. A pixel with skin? A completely different ratio. A pixel with brown wood? Different again. The method extracts the matte from these differences, not from absolute color values — which is why it remains robust against lighting variations.

In practice: You adjust two parameters — Core Matte (where is definitely foreground) and Edge Behavior (how hard or soft the edge becomes). The system then calculates the feather region itself by gradually evaluating the color channel difference. With decently lit green plate, you immediately see if you have a clean key or if spill and fringing will bother you — and if an additional despill pass is necessary. Ultimatte combines well with color correction beforehand because it builds on mathematical channel differences, not on a predefined "greenscreen color."

The engine is found in almost every compositing package — Nuke has it as a standard keyer, After Effects uses similar algorithms, even DaVinci Fusion builds on it. The reason: this method has been proven since the days of Ultimatte (the company that invented it), and it remains the fastest, most intuitive way to precise mattes in color difference keying. For motion capture suits, for bluescreen next to water, for any shot where you don't want to resort to complex rotoscoping — Ultimatte is your first tool.