Compositing Integration: Layers, Masks, Blending and Colour Matching
Domain focus
This domain covers compositing integration: layers, masks, blending, and colour matching. The exam tests layer order, alpha handling, blend modes, and matching a foreground element to a background.
Core rules and concepts
- Layer order determines what covers what. Put the foreground over the background, and use masks to shape visibility.
- Alpha channels define transparency. Check whether the project uses straight or premultiplied alpha and handle edges consistently.
- Blend modes such as over, multiply, screen, add, and overlay change how colour values combine. Use them deliberately, not as a fix for a bad matte.
- Colour matching checks black point, white point, midtones, hue, saturation, and contrast. Match the light direction and colour temperature, not just brightness.
- Add grain, light wrap, edge blur, and atmospheric haze to integrate edges. A perfect matte can still look pasted without these.
Worked example
An actor shot on a green screen is placed into a sunset background. The actor looks too blue. Sample the background's warm highlight and shadow; adjust the actor's colour balance toward warm, lift the black point slightly, add a thin warm light wrap on the edge, and match grain. Reasoning: the mismatch is colour temperature and edge light, not alpha. Matching only brightness would leave the actor looking pasted.
Traps that cost marks
- Matching brightness but ignoring colour temperature.
- Applying a blend mode to hide a bad matte.
- Double-premultiplying an element with an alpha channel.
- Forgetting edge blur and light wrap.
- Using the same grain for foreground and background when they were shot on different media.