Channel Key Node
The Channel Key node determines background objects from foreground objects by the difference in the selected channel’s levels.
For example in the YUV Color Model, this node is useful when compositing stock footage of explosions (very bright) which are normally shot against a solid, dark background.
Inputs
- Image
Standard color input.
Eigenschaften
- Color Space
This button selects what color model the channels will represent.
RGB, HSV, YUV, YCbCr
- Key Channel
This button selects the channel, defined by the Color Space, to use to determine the matte.
- Algorithm
Method to calculate the difference between levels.
- Max
Limit by the maximum of the other two channels other than the Key Channel.
- Single
Limit by the maximum of the selected Limiting Channel.
- Limiting Channel
The channel to use when computing the maximum, the options are defined by the Color Space.
- High
Determines the lowest values that are considered foreground. (Which is supposed to be – relatively – high values: from this value to 1.0.)
- Low
Determines the highest values that are considered to be background objects. (Which is supposed to be – relatively – low values: from 0.0 to this value.)
Tipp
It is possible to have a separation between the High and Low values to allow for a gradient of transparency between foreground and background objects.
Outputs
- Image
Image with an alpha channel adjusted for the keyed selection.
- Matte
A black-and-white alpha mask of the key.