The Emit Photons attribute enables the generation of photon maps for this light source. Generally, only point lights, area lights and spot lights should enable this toggle. Note that the total number of photons to trace into the scene is specified in Section 3.9.3.7 [Render Pass Global Illumination], page 78. 3Delight for Maya will automatically compute how much photons are needed per light, depending on their intensity. This attribute is off by default.