[Radiance-general] Re: Desktop Radiance and IES plus new question on RGB

[Greg Ward]

Hi Nick,

The glow values (multiplied by whatever pattern is applied) are in  
units of watts/steradian/sq.meter, or SI radiance.  There is no  
maximum, and values below zero are even permitted in cases where you  
are outside the standard RGB gamut.  You can compute luminance (in cd/ 
m^2) from these values by applying the formula:

	Lumiance = 179*(0.2651*Red + 0.6701*Green + 0.0648*Blue)

I hope this helps.
-Greg

> From: "Nick Calcagni" <nac342 at drexel.edu>
> Date: May 22, 2008 11:38:57 AM PDT
>
> Thank you, both of you. But I was referring to the IES files from  
> lighting manufacturers as Greg said. Sorry for not being clear...  
> ies2rad seems to be exactly what I'm looking for.
>
> Should the following be a new topic?
>
> For something like the following (which is part of a converted IES  
> file, I think). But regardless, "glow" requires you to specify  
> "red" "green" and "blue" values. In the following they are equal:  
> 9477... for each.
>
> lamp_glow glow lamp
> 0
> 0
> 4 9477.696528 9477.697093 9477.697093    0
> So what units are these values in? This ratio of R to G to B shows  
> up in other parameters too (light, illum). Is there a max value to  
> these RGB values or for their total? That's one basic thing I've  
> always been confused about.
> Thank you,
> Nick