Units light

[nicola_barbano]

Hi!
Sorry for the silly and repetitive question about Units light. But I'm a bit lost on that.
I have a document/spec of the lighting saying 100lm/W and the real photos of reference.
Which units correspond exactly in VRay?
From my test Radiance (W/m2/sr) is the one that it's more similar to my reference...so I suppose that lm/W = Radiance, but I would like to know if this correct or not.

Thank you!
Nico

[hermit.crab]

I'm not sure a direct conversion of Luminous efficacy exists since it's an efficiency coefficient (I can't seem to find a conversion calculator). Maybe there's a value, which states the specific light's value in other units?

[nicola_barbano]

In my document I have also this...2400lm/m...but even this unit there's not in VRay Units Light...so I'm a bit confused

[hermit.crab]

I'm no physicist but after using a few calculators it seems that the value you sent [lm/m^2] should be used. The per steradian [lm/m^2/sr] notes that the size of the light is considered as well.

[nicola_barbano]

Thank you!
Yes...2400lm/m = 100lm/W.
So I keep using Radiance (W/m2/sr) for this job that seems correct, as you said. I can change it in lm/m^2/sr but it's exactly the same amount of light

Nico