# Ellipsoidal Spotlight ies file

I hope I'm doing this correctly.. can anyone give me some advice?
I'm modeling a Source 4 10 degree ellipsoidal spotlight
On the web, I found this pdf which contains photometric data

By looking at the cosine curve on page 2, I gathered these numbers - degrees
vs candela
0 .5 1 1.5 2 2.5 3
3.5 4 4.5 5 5.4 90.00
82000 81000 80000 76000 70000 62000 53000 45000 36000 27000
16000 0 0
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

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

So I put it into a eis file like this:
TILT=NONE
1 21900 1 12 1 1 1 -.6 0 0
1 1 750
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5
5.4 90.00
82000 81000 80000 76000 70000 62000 53000 45000 36000 27000 16000
0 0

I left my RwR book at home, so I don't remember the meaning of all the other
numbers.
Does this seem correct? Since this is the first time I've tried doing this,
I mostly want to know if I'm looking for the right numbers, and using them
correctly

Thanks, Rob Fitzsimmons

Hi Rob,

sounds fine to me. No, you don't need to double the numbers, as your numbers correspond to one half of the spotlight cone (0 deg = centre of spotlight to 5 deg).
I played around with the lumens number and did not find that it was affecting anything.

good luck!

alexa

Fitzsimmons, Rob wrote:

···

I hope I'm doing this correctly.. can anyone give me some advice?
I'm modeling a Source 4 10 degree ellipsoidal spotlight
On the web, I found this pdf which contains photometric data

By looking at the cosine curve on page 2, I gathered these numbers - degrees
vs candela
0 .5 1 1.5 2 2.5 3
3.5 4 4.5 5 5.4 90.00
82000 81000 80000 76000 70000 62000 53000 45000 36000 27000
16000 0 0
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

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

So I put it into a eis file like this:
TILT=NONE
1 21900 1 12 1 1 1 -.6 0 0
1 1 750
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5
5.4 90.00
82000 81000 80000 76000 70000 62000 53000 45000 36000 27000 16000
0 0

I left my RwR book at home, so I don't remember the meaning of all the other
numbers.
Does this seem correct? Since this is the first time I've tried doing this,
I mostly want to know if I'm looking for the right numbers, and using them
correctly

Thanks, Rob Fitzsimmons

_______________________________________________
[email protected]

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Alexa I. Ruppertsberg
Department of Optometry
BD7 1DP
UK

Phone: ++44 (0) 1274 - 23 53 78
email: [email protected]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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