The Light AOVs isolates a light source's contribution. Each light AOV behaves as if all the other lights in the scene are switched off. You can combine individual light AOVs to recreate the original render in post, or to further adjust the individual contributions of each light during post. 


To use light AOVs, each light emitter needs to be identified and mapped to the desired Light AOV. This is done by assigning the Light Pass ID in each Emission node in the scene (figure 1).


Light Pass ID


Figure 1: Assign Light pass ID in the Emission nodes

 


A Light AOV node with a corresponding Light ID needs to be added to the Render AOV Group node (figure 2).


Light Pass ID


Figure 2: Setting the Light AOV node's ID to coorespond with the appropriate light source

 


To see the AOV, enable the lighting AOVs according to the existing assigned IDs in the Render Viewport (figure 3).


Light AOV Render Viewport


Figure 3: Enabling the light AOV in the render viewport