Light Passes
It's possible to assign each light source of the scene to different light pass (group) and output selected light pass AOVs together with the main render image with no extra render cost. This is usefull for lighting change in post production
In case the Blender Light pass is enabled it's possible to alter the lighting contribution for each individual beauty or light pass using the post process. This can be done in real-time without restarting the render inside Interactive Preview Render window where Blender Light passes image is selected.
The controls to alter the contribution of each individual light pass that are recordered to Blender Light passes are placed in this menu below and include the light temperature, color and intensity scale.
The light pass assignment can be changed for each light source in the scene: