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Kerkythea Rendering System • View topic - Self Luminance – ask for clarification
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Self Luminance – ask for clarification

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<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 12:20 am

Self Luminance – ask for clarification

Hi,

I have a problem with the Self Luminance settings. Esp. Lumen

For Info: I try to compare different light setups in a room (60W standard bulb, 12W LED bulb, ...). I modeled my lamp and a (small low poly) bulb.

If I set the Units in the Self Luminace section to Watts and the Power to 60 everything is ok.
But when I choose Lumen as Unit and use the 806 (Lumen) of a real 'Philips Master LED Bulb 12W' as Power I get a complete dark result although the result should be nearly the same.

Technical data of the LED Bulb: 806 Lumen, 300° angle of radiation, 69 cd, 12W, 2700K.
Render Setting is: PMM+AA.

Could anyone enlight me?

Greetings Oliver.
<<

Fletch

KT-Team
KT-Team

Posts: 8564

Joined: Fri Oct 27, 2006 2:38 am

Location: Milwaukee, WI USA

Post Sat Feb 19, 2011 1:01 am

Please post the scene if you can.


<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 1:15 am

thanks for your fast reply!

Here are the two Materials:
first 12W LED bulb with 806 Lumen,
second is the 60W standard bulb
Attachments
Bildschirmfoto-Material Editor_60W.png
Bildschirmfoto-Material Editor_12W.png
<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 1:19 am

here is the result for the 60W standard bulb (the second result is still in computation, I post it as soon as it is ready).
Attachments
AZ-23_PMM-A_Schreibtisch_exp1.0_60W.jpg
PM-M+AA, exposure: 1.0, gamma: 1.0
<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 1:21 am

in the meantime I post the same scene with a strong top light (using standard lighning).

All pictures are rendered with the same settings.
Attachments
AZ-23_PMM-A_CamCur_exp1.0_Laminat_Buche1.jpg
<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 1:30 am

... and here is the result with the 12 W LED bulb 806 Lumen material setting
Attachments
AZ-23_PMM-A_Schreibtisch_exp1.0_12W.jpg
PM-M+AA, exposure: 1.0, gamma: 1.0
<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 1:31 am

and here are my Render Settings:
Attachments
Bildschirmfoto-Render Settings.png
<<

Fletch

KT-Team
KT-Team

Posts: 8564

Joined: Fri Oct 27, 2006 2:38 am

Location: Milwaukee, WI USA

Post Sat Feb 19, 2011 2:30 am

my guess is that the lumens version is accurate. the watts version is too. only, your watts settings are wrong. the average 60w incandescent bulb loses something like 97% of it's power to heat. So it's efficiency is 3% you have efficiency at 1. change it to .03 and you may see something closer to the lumens output.

Remember also that if you have it set to be straight "watts" instead of "watts per meter squared" you are getting 60 watts total from all combined faces with that material. So if you were to have 10 bulbs in the room, each with 8 faces per bulb, with the 60watt material, all 10 bulbs combined would = 60 watts. This is why the per meter squared option is provided.


<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Sat Feb 19, 2011 2:59 am

Ok, in the two problematic pictures (#1 & #3) I have only 1 bulb.

.. hmm, if I got you right, it means, I must give the true effiecency of the illuminant ... this could be a challange for the very new LED illuminants ...

and the Menu is rather misleading, without a propper instruction.

So, is it right that I don't need the efficiency if I use lumen as unit?

And, how do I convert Watts of a standard incandescent bulb into Watts/m²??

Btw, the lumens/m² is lux the Luminous emittance, right?

Thanks for your quck response!

Oliver.
<<

Fletch

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KT-Team

Posts: 8564

Joined: Fri Oct 27, 2006 2:38 am

Location: Milwaukee, WI USA

Post Sat Feb 19, 2011 2:38 pm



<<

obo68

Posts: 9

Joined: Mon Jan 05, 2009 11:24 pm

Post Wed Dec 21, 2011 4:29 pm

Re: Self Luminance – ask for clarification

sorry, but I have still some questions about self luminance matrials.

If I have 2 light sources in my scene (i.e. LEDs) and I know the lumen for them, do I have to choose 'lumen' or 'lumen/m²' in the Self Luminace Menu for the unit?

Thanks,
Oliver.
<<

Fletch

KT-Team
KT-Team

Posts: 8564

Joined: Fri Oct 27, 2006 2:38 am

Location: Milwaukee, WI USA

Post Thu Dec 29, 2011 8:52 pm

Re: Self Luminance – ask for clarification

Lumens is easier.
with multiple surfaces, it will divide the lumens up over the number of surfaces. so, give double the lumens for 2 lights, triple for 3, and so on.



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