20.02.2024 – Green Screen part2

Week 17 – Green Screen part2

Green Despill:

• Utilize the Keylight node to remove green, merge it with the original plate using the ‘Difference’ operation. Subsequently, desaturate it, and merge it back with the green-removed plate. Since removing green darkens the despill area, merge it with the ‘Plus’ operation to match the luminance.

• You can also achieve green despill with the IBKColour and IBKGizmo nodes. Remove green using these nodes, merge the original plate and the green-removed plate with the ‘Minus’ operation. Desaturate the green area and adjust the background using the Grade node if needed. Finally, merge it with the green-removed plate using the ‘Plus’ operation.
• The DespillMadness gizmo facilitates easy despilling of the green screen plate, and you can export the spill matte in the alpha channel.

---

Green Screen Workflow:

1. Denoise the original plate to enhance clarity.
2. Create an alpha with channels or Keyer nodes.
3. Despill the original plate.
4. Use the EdgeExtend node to remove slight pixels around the edge for a natural blend with the background.
5. Optionally use EdgeBlur to soften the outline.
6. Premultiply the despilled plate with the created alpha and merge it with the background.

EdgeExtend Node: By default, the EdgeExtend node is premultiplied. Untick it to extend the area and match the color with the background plate.

---

Even Out Green Screen: Select two different shades of green, average them, subtract the average from the keyed plate, and add the result over the original plate, masking via inverted alpha.

Stacked IBK: Stack multiple IBKColour nodes to create alpha for clearer and more accurate results, especially useful for motion blur and defocused plates.

Addmix Node: Similar to Merge (over), the Addmix node provides more details in certain cases.

---

Key Structure: Always structure your key into three pipes:

• Alpha/matte pipe
• Color/despill matte
• Background plate

Alpha Breakdown: Break down alphas by creating a core matte and an edge/hair matte. Denoise and white balance the plate before keying. Address despill separately for core and edges, adjusting for lighter core and stronger edges. Manipulate edge despill to match background colors during the despill phase.