Settings and Macros/SubtractBGColor Description

From VFXPedia

SubtractBGColor Description

Other macro tools in this category:
[ColorFill]
[InvertColor]
[InvertedBC]
[LuminanceControl ]
[PrimaryGrade]
[SubtractBGColor]
[TMI Color]

Sometimes 3D objects you get are rendered with the Alpha channel against a non-black background (colored or textured) for some reason. Even if you post-multiply the image, some background texture will remain around the edges and in semi-transparent areas. Using the rendered object plate and the clean background plate, the macro completely removes unwanted background artefacts.

Another case when the SubtractBGColor can help is if you need to replace the background behind a practically shot motion blurred, defocused or semi-transparent object. The issue is the same: blurred edges and semi-transparent areas contain details from the background, so you have to shrink the masks to get rid of the artefacts. Sometimes the shrunk objects get significantly thinner which is undesirable. This tool resolves the problem.

The macro requires the Alpha channel embedded in the input image and the clean background. The input image should not be premultiplied.

External Inputs

The following inputs appear on the tool's tile in the Flow Editor:

Input: Source image. Required.
Background Color: Clean background without the foreground objects. Required.
Effect Mask: Defines the areas where the background color is subtracted. Optional.