Iray Emissions settings translation to Reality

Discussions about general topics of interest, like lighting, material customization and so one
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Iray Emissions settings translation to Reality

Postby Rivaliant » Mon May 07, 2018 7:58 am

I'm sure this topic has been brought up plenty of times and may have even been answered
But i have been having trouble as of late with perfecting lighting
I have been using the default settings but this is one area that i just never got my head wrapped around and i was actually curious about this
and with the Luxrender wiki seemingly went off line i'm left in the dark

with Iray scenes, you have some scenes with lights that come with preset emissions setting for iray and was wondering how they can be translated though Reality's terms to get a 1:1 in luxrender

but before I dig into it

i want to understand how Reality and Luxrender define lighting behavior alil better

Gain is a multiplication of the lights exposure that much I understand
But Power in watts and how it relates to its appearance in Luxrender is the part that makes me scratch my head
I know Efficiency is Lumens per Watt
But then what is the difference between say the default of 100 watts and 17 Efficiency at 1 gain ( which is 1700 Lumens )
to say
10 watts at 1.7 efficiency at 100 gain? ( which is 170 lumens times 100 exposure )

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Re: Iray Emissions settings translation to Reality

Postby sigstan » Wed May 09, 2018 2:09 pm

Hmm, as far as I remember the Watts and Efficiency parameters are purely included to support the ability to simulate real life light sources by entering their appropriate values. This would mean that you should be able to obtain exactly the same lighting results using different combinations of Watts, Efficiency and Gain.

However, in the real world a normal light bulb will only have up to 17% eff, and a halogen projector maybe up to 25%, so making up unrealistic values for this parameter is not really beneficial for anyone's understanding.

Therefore I would normally keep Efficiency at default 17% and only adjust Watts and/or Gain as per my needs, but that is just my take on it.

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