Illuminance and coloured lights

radiance-general
1

Hi everybody !

I've got a problem I'm not sure how to deal with.

I'm using a Disano light to simulate a tunnel lighting. It is a fluorescent light.

I converted it to radiance format from ies format (previously translated from eulumdat format) using ies2rad with no specific value. Then I calculated illuminance on road surface visualizing isolux scheme.

Then I converted the same light with the "-t white" option. And calculated illuminance's isolux as before.

The two isolux schemes are different, being value for the white case almost 10 % bigger.

Shouldn't them be equal?

I tried simulating same case in dialux and calculux, and they do report almost same values as the white case.

What's wrong? Am I missing some knowledge / trick / anything?

Lucio

Ps : I also discovered some problems both in ies2tab and in eulumcnv. The second, badly converting photometry (some dark circles appear in the lighted scene as missing photometric values), the first badly converting geometry (flipping x and y definitions). But I have to check this things a little more.

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2

Hi Lucio,

The lamp color data also includes depreciation factors, which probably account for the 10% difference. I assume the "white" value is larger.

A long-standing bug has been recently pointed out by Zack Rogers related to the orientation of full photometric distributions, and has been included in the latest HEAD available from radiance-online.org. A statement has also been added to clarify the assignment of the width (along y) and length (along x) axes.

Hope this helps.
-Greg

···

From: "loscotec\@libero\.it" <[email protected]>
Date: February 6, 2008 6:28:49 AM PST

Hi everybody !

I've got a problem I'm not sure how to deal with.

I'm using a Disano light to simulate a tunnel lighting. It is a fluorescent light.

I converted it to radiance format from ies format (previously translated from eulumdat format) using ies2rad with no specific value. Then I calculated illuminance on road surface visualizing isolux scheme.

Then I converted the same light with the "-t white" option. And calculated illuminance's isolux as before.

The two isolux schemes are different, being value for the white case almost 10 % bigger.

Shouldn't them be equal?

I tried simulating same case in dialux and calculux, and they do report almost same values as the white case.

What's wrong? Am I missing some knowledge / trick / anything?

Lucio

Ps : I also discovered some problems both in ies2tab and in eulumcnv. The second, badly converting photometry (some dark circles appear in the lighted scene as missing photometric values), the first badly converting geometry (flipping x and y definitions). But I have to check this things a little more.

3

Greg Ward wrote:

Hi Lucio,

The lamp color data also includes depreciation factors, which probably account for the 10% difference. I assume the "white" value is larger.

Indeed, the multiplier for incandescent (which I believe white is aliased to) is .95, and the multiplier for fluorescent is .85...

These lamp specs can be found in the file "lamp.tab", usually living in the /usr/local/lib/ray directory.

···

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

4

Mmm.. I see.. Thank you very much.. but...

what actually is depreciation?

Should I run the command "ies2rad -m 1.1764706 -t fluorescent lamp.ies" to have right illumination ? If this is right, is there a reason why ies2rad does not do it automatically?

If it isn't right, are Calculux and Dialux using badly lights ? 15 % illuminance less is really something.. !!

And, there is some documentation about all this stuff ? It would be an interesting chapter for my thesys I guess..

Sorry for the many question and for my ignorance.

Lucio

.Greg Ward wrote:
.> Hi Lucio,
.>
.> The lamp color data also includes depreciation factors, which probably
.> account for the 10% difference. I assume the "white" value is larger.
.Indeed, the multiplier for incandescent (which I believe white is
.aliased to) is .95, and the multiplier for fluorescent is .85...
.
.These lamp specs can be found in the file "lamp.tab", usually living in
.the /usr/local/lib/ray directory.
.
.----------------------------------
. Rob Guglielmetti
.www.rumblestrip.org
.
._______________________________________________
.Radiance-general mailing list
[email protected]
.http://www.radiance-online.org/mailman/listinfo/radiance-general
.

.. Caminante no hay camino, solo se hace camino al andar ..

5

[email protected] wrote:

Mmm.. I see.. Thank you very much.. but...

what actually is depreciation?
  
We're talking about lamp lumen depreciation (LLD) here, i.e. the gradual decrease in lamp output over the life of the lamp--which can be significant in certain lamps. This is the reason why you will see two columns for lumen output in any respectable lamp manufacturer's catalog, for sources where this is an issue. Often called "initial" and "design" lumens, the design lumens are adjusted for a particular lamp's lumen depreciation over its rated life. Design lumens will always be lower than initial, unless if you're looking at a first edition Philips lamp catalog from 2005 (or 2004, can't remember) which, very embarrassingly, inverted the labels on the two values! (I still have my copy somewhere, but I doubt it will become a collector's item (except among a bunch of lighting geeks.))

Anyway, back to LLDs... The LLD is but one of the elements that comprise the overall light loss factor (LLF) that is commonly used in lighting calculations to account for these and other losses inherent to a lighting design (room surface dirt, ballast factors, etc). In Radiance, this is accounted for with the multiplier (-m) in ies2rad (though you can also use it to simulate higher or lower wattage lamps, or dimming, etc).

***Which brings up a good point: if you are using colored lights in Radiance by referencing lamp.tab it's not a bad idea to check what lamp.tab thinks the LLD is and make sure it jives with your actual lamp, AND make sure that factor is REMOVED from the LLF that you are (hopefully) using in your multiplier.***

Should I run the command "ies2rad -m 1.1764706 -t fluorescent lamp.ies" to have right illumination ? If this is right, is there a reason why ies2rad does not do it automatically?
  

Hopefully the above paragraphs shed light on the answers to these questions, which are "no", and "yes", respectively. =8-)

If it isn't right, are Calculux and Dialux using badly lights ? 15 % illuminance less is really something.. !!
  
See above...

And, there is some documentation about all this stuff ? It would be an interesting chapter for my thesys I guess..

The ies2rad man page does explain the lamp color and the lamp.tab lookups. There is more info in lamp.tab itself. General info about light loss factors can be found in any decent lighting design calculation text.

Hope this helps!

Rob Guglielmetti
www.rumblestrip.org

6

Hey Rob !!!

I still haven't given thanks to you for your very detailed informations about lumen depreciation and so on.. !!

THANK YOU !!!!

It is really a gift to have people like you willing to help and doing it so much and so exhaustively ! My thesys (and my radiance learning curve) would require much more time (but really much more) if I wouldn't have your help !!

Guess I should find some similar kind of community to improve my english as well !! :stuck_out_tongue:

Lucio

···

[email protected] wrote:
.> Mmm.. I see.. Thank you very much.. but...
.>
.> what actually is depreciation?
.>
.
.We're talking about lamp lumen depreciation (LLD) here, i.e. the gradual
.decrease in lamp output over the life of the lamp--which can be
.significant in certain lamps. This is the reason why you will see two
.columns for lumen output in any respectable lamp manufacturer's catalog,
.for sources where this is an issue. Often called "initial" and "design"
.lumens, the design lumens are adjusted for a particular lamp's lumen
.depreciation over its rated life. Design lumens will always be lower
.than initial, unless if you're looking at a first edition Philips lamp
.catalog from 2005 (or 2004, can't remember) which, very embarrassingly,
.inverted the labels on the two values! (I still have my copy somewhere,
.but I doubt it will become a collector's item (except among a bunch of
.lighting geeks.))
.
.Anyway, back to LLDs... The LLD is but one of the elements that comprise
.the overall light loss factor (LLF) that is commonly used in lighting
.calculations to account for these and other losses inherent to a
.lighting design (room surface dirt, ballast factors, etc). In Radiance,
.this is accounted for with the multiplier (-m) in ies2rad (though you
.can also use it to simulate higher or lower wattage lamps, or dimming, etc).
.
.***Which brings up a good point: if you are using colored lights in
.Radiance by referencing lamp.tab it's not a bad idea to check what
.lamp.tab thinks the LLD is and make sure it jives with your actual lamp,
.AND make sure that factor is REMOVED from the LLF that you are
.(hopefully) using in your multiplier.***
.
.> Should I run the command "ies2rad -m 1.1764706 -t fluorescent lamp.ies" to have right illumination ? If this is right, is there a reason why ies2rad does not do it automatically?
.>
.Hopefully the above paragraphs shed light on the answers to these
.questions, which are "no", and "yes", respectively. =8-)
.
.> If it isn't right, are Calculux and Dialux using badly lights ? 15 % illuminance less is really something.. !!
.>
.
.See above...
.
.> And, there is some documentation about all this stuff ? It would be an interesting chapter for my thesys I guess..
.>
.>
.The ies2rad man page does explain the lamp color and the lamp.tab
.lookups. There is more info in lamp.tab itself. General info about
.light loss factors can be found in any decent lighting design
.calculation text.
.
.Hope this helps!
.
.Rob Guglielmetti
.www.rumblestrip.org
.
._______________________________________________
.Radiance-general mailing list
[email protected]
.http://www.radiance-online.org/mailman/listinfo/radiance-general
.

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camino, solo se hace
camino al andar ..

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destino no es al
final de el viaje,
pero en todo el
andar ..