[Radiance-general] Ellipsoidal Spotlight ies file

[Rob Guglielmetti]

Hi Rob,

Fitzsimmons, Rob wrote:
> I'm not sure if I should double the angles - in that the chart goes from 0
> to 5, yet this is a 10 degree light

I see Alexa answered this one for ya...

> from the table on the upper right of page 2,
> 750 Watt lamp -- 21900 lumens (tho I guess eis2rad doesn't use this number?)

ies2rad doesn't use the number, but the recommended practice for the 
standard format is to make sure that the lumen value entered there is 
the correct value for the lamp that was in the fixture when it was 
photometered (which in your case is correct at 21,900).  This way you 
can always accurately scale the candela values to account for different 
lamps, color filters, even lamps that aren't on that chart.  Since there 
is sometimes variance in lamp efficacy from manufacturer to manufactuer, 
it's nice to always have that lumen assumption in the file.  I think 
this is more useful in architectural applications, but I just mention it.

I realize this is nitpicking, but it's just a good habit to get into, 
especially  if you plan to use these ies files in some sort of library.

-------------------
    Rob Guglielmetti
www.rumblestrip.org