Questionaire on fluorescent lamp

Hello Everybody,

It's my first time to mail to the radiance mailing list.
I'm using Radiance to calculate near field illuminance (in fact radiation)
from bare fluorescent lamps.
Before doing with real mode data, I tested one with a bare fluorescent lamp
and a plan 20 centimeter away from the long and cylindrical lamp. But the
result right under the lamp was strange, that is, the other values were as I
expected but only in the area directly under the lamp the illuminance was
highest at the center and decreased gradiently as went to the end of the
lamp. For example, the illuminance was 5000 lux at the center right under
the lamp, but it decreased to 15 lux at a quarter point of the lamp,
though the two would be almost same.
Maybe I am not understanding properly the lamp description. Can you anyone
explain this to me? Or Radiance is not adequate for near field calculation
with long cylindrical lamp?

Best Regards

Minki Sung

try to have a look for the -ds setting...

if this still a problem for your application I'd investigate the use of
'glow' (0 0 4 r g b 0) in conjunction with an indirect calculation (-ab
n, n>0)

to avoid ambient cache problems you may switch to -aa 0 -u but this
will require over sampling of your grid to remove Montecarlo noise.

hope this makes sense,

ciao

G.

ยทยทยท

________________________________

From: [email protected]
[mailto:[email protected]] On Behalf Of Minki
Sung
Sent: 15 October 2007 12:16
To: [email protected]
Subject: [Radiance-general] Questionaire on fluorescent lamp

Hello Everybody,

It's my first time to mail to the radiance mailing list.

I'm using Radiance to calculate near field illuminance (in fact
radiation) from bare fluorescent lamps.

Before doing with real mode data, I tested one with a bare fluorescent
lamp and a plan 20 centimeter away from the long and cylindrical lamp.
But the result right under the lamp was strange, that is, the other
values were as I expected but only in the area directly under the lamp
the illuminance was highest at the center and decreased gradiently as
went to the end of the lamp. For example, the illuminance was 5000 lux
at the center right under the lamp, but it decreased to 15 lux at a
quarter point of the lamp, though the two would be almost same.

Maybe I am not understanding properly the lamp description. Can you
anyone explain this to me? Or Radiance is not adequate for near field
calculation with long cylindrical lamp?

Best Regards

Minki Sung

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Thank you for your answer.

I've checked it out as you mentioned, but I can't solve the problem yet.
The situation is assumed to take place in the distance shorter than
1.5times of cylinderical light source's diameter. I think there may
need to
some technique to model cylindrical light sources.

Actually, I'm modeling UV lamp emitting only ultraviolet wavelength
in small equipments.
So the cylindrical black light source was defined to have only blue
radiation (for an alternative to UV). Of course all the materials have
reflectance values only for blue radiation.
I want to find the UV intensity on some surfaces, and I think Radiance is
well organized to calculate this value, but I'm not sure if
there is anything to consider like that cylindrical light source is not good
in Radiance.
I really appreciate if I get some advices on my case.

Minki, Sung