Viewing a Key with a Solid Colour Background
The following optional technique can help you create cleaner keys more quickly.
While creating the key, you can view the composite using a solid colour for the background in place of the back clip. This can help you see details in the image, such as colour spill, that you may otherwise miss. You can use the default colour (black) or select a colour using the colour picker.
Note: This view does not affect the final render.
To use a solid colour background:
Double-click the Result node.
The Matte Luminance Curves menu appears.
In the Result box, select Comp.
A colour pot appears.
Click the colour pot under the Comp view output option.
The colour picker appears.
Select a colour for the background using the colour picker.
Your key is displayed on a solid colour background in the Result view.