for any kind of light source you can have the power in Watt, and the efficiency
, and it depends on the light sorce dimensions, but in Octane you can tick the Surface brightness option to remove this dependency.
Since the luminous efficacy is quite dependent on the spectrum, and since Octane is a spectral render engine, instead of an RGB node, it is far better to use a Gaussian spectrum node in the Texture/Efficiency
If you prefer to work in Lumen
, just use the Lumen
value instead of Watt, and use the 1/683 ratio in the Power value of the Gaussian spectrum node.
With this approace, you can correctly mimic any kind of light. In my opinion there is nothing esoteric here, just physics and math.