[Radiance-general] Re: ies photometry+geometry

[steve michel]

Thomas,

Thanks for the tip.  Using bare lamp photometry can be useful in 
architectural  lighting geometry (eg. cove lighing, cornices etc..) that 
don't require complex fixtures other than a lamp holder and wiring.


Steve


>From: Thomas Bleicher <tbleicher at arcor.de>
>Reply-To: Radiance general discussion 
><radiance-general at radiance-online.org>
>To: rpg at rumblestrip.org,Radiance general discussion 
><radiance-general at radiance-online.org>
>Subject: [Radiance-general] Re: ies photometry+geometry
>Date: Sat, 28 Apr 2007 11:39:43 +0100
>
>
>Great post, Rob!
>
>Just one small addition:
>
>On 27 Apr 2007, at 01:21, Rob Guglielmetti wrote:
>
>>steve michel wrote:
>>>A linear fixture is exactly what I had in mind. For a while I even  
>>>searched for 'bare bulb' photometry files from big lamp  manufacturers 
>>>(GE or Philips) but none exist for fluor tubes (only  par and mr16 
>>>spots). But is the illum distribution method another  one or a subset of 
>>>using flatcorr and lboxcorr techniques you  describe??
>>
>>No photometric files exist for bare fluorescent tubes probably  because 
>>you can't really test that condition, nor would anyone want  to spend the 
>>money to do so.  A fluorescent tube will always be in  a fixture, even if 
>>it's a simple striplight -- a simple ballast  housing and two lampholders.
>
>If all you need is a T5 tube without complex reflector geometry  behind it
>you can create a cylinder with the right brightness to match the output
>lumens of your lamp. The 'lampcolor' script calculates the right RGB  
>values
>for you. Here is a sample session for a T5 35W lamp:
>
>ble at zwielicht:~ $lampcolor
>Program to compute lamp radiance.  Enter '?' for help.
>Enter lamp type [WHITE]:
>Enter length unit [meter]:
>Enter lamp geometry [polygon]: cylinder
>Cylinder length [1]: 1.449
>Cylinder radius [0.1]: 0.008
>Enter total lamp lumens [0]: 3300
>Lamp color (RGB) = 80.569890 80.569895 80.569895
>Enter lamp type [WHITE]: ble at zwielicht:~ $
>
>The RGB values of 80.57 now go in a definition for the light material
>which in turn is used by the cylinder definition:
>
>## light material for 35W T5 lamp
>void light light_35W_T5
>0
>0
>3 80.57 80.57 80.57
>
>## light applied to cylinder centred at (0,0,0) and aligned with x-axis
>light_35W_T5 cylinder lamp_T5
>0
>0
>7 -0.7245 0 0   0.7245 0 0   0.008
>
>
>These four lines will create a bare T5 lamp that can be used as light
>source in Radiance scenes. The output distribution of a real lamp might
>be a tiny bit different (at the end caps for example) but I'd say it's
>close enough for lighting calculations.
>
>You should not stick this lamp in complex reflector geometry and let
>Radiance do the calculations of the resulting distribution for you.
>The algorithms in Radiance are not suited for this kind of calculation.
>
>Regards,
>Thomas
>
>
>
>_______________________________________________
>Radiance-general mailing list
>Radiance-general at radiance-online.org
>http://www.radiance-online.org/mailman/listinfo/radiance-general

_________________________________________________________________
Don’t waste time standing in line—try shopping online. Visit Sympatico / MSN 
Shopping today! http://shopping.sympatico.msn.ca