Can you explain this? Action Matte Input not showing up when fill is yellow

Going crazy or I’ve found a bug.

Take a frame of white and put it into an action over bars like in the diagram.

Now change the white to yellow.

The layer disappears in action

It is happening because flame does not look at the luminance of the input image to create the matte. It looks at the blue channel. Yellow has no blue. If you put a mono node between the colour source and the matte input it will behave as you expect. Under Action>Node Prefs>Objects & Mattes, you can change the matte channel to red or green, but if you want a true lum key, you need to put in the mono node.


WOW after all these years I’ve been thinking the input was luminance based. Thanks for explaining.