There is always an issue with keying defocused and motion blurred objects: the color on the edges is mixed with the color of the background.
Basically, the problem arises even with static objects which are in focus, because there is always some softness in the practical image.
The most obvious solution to this is either to suppress (desaturate) the background color or to shrink the objects' edges.
In first case, you may have a problem if the background luminance is different, for instance, if you key dark objects against white (like trees against the sky)
In second case, the blurring may be so strong, that the objects disappear completely with shrinking.
This macro expands the actual color of the objects so that it extends through the entire blurred areas, replacing the background color mixture.
The workflow is the following:
- Connect the macro after the keyer
- Set the Output Image parameter to Pre-Shrunk Image
- Adjust the Pre-Shrink parameters so that the shrinking was as little as possible to just cut BG color spill completely
- Switch the Output Image to Extended Color to check with what colors you are going to fill the edges, adjust the shrinking if nessesary
- Switch the Output Image to Final Result
- Set the Extend parameters so that you see no sharp borders in the blurred areas. Keep the parameters values as small as possible
- Adjust the Soften Border group so that you don't see a border between the internal untouched areas and the recolored blurred areas
You can set the parameters in standard Fusion units (relative to the image width) as well as in actual pixels, which may be useful with little amounts of blurring in the source image.
The X and Y multiplier values are used for objects which are motion blurred primarily in horizontal or vertical direction.
The macro also solves the problem of edging which happens due to the data compression or chromatic aberrations.