I have just installed LuxRender. I know how to do change the strength of lamps with Cycles but it seems that settings change for each render engine. Could someone please help me to adjust the light's strength in LuxRender?


1 Answer 1


Firstly, I'm not sure that LuxRender is within the scope of this forum. You might have better luck over at http://www.luxrender.net/forum

That being said, I might still be able to help. LuxRender is very much based on the way light works in the real world. Consequently, adjusting the intensity of the lights is not terribly straightforward.

Under emission settings, "Power" is the wattage of your light source: 40 = ~40 watt light bulb. For that reason, size matters. 40 watts spread over a large area won't be as bright.

Under emission settings, "Efficacy" is lumens per watt. Not sure exactly how this changes the light besides making it lighter or darker, but I have to believe it does something else, too.

Under emission settings, "Gain" is a multiplier for the "Power" setting. Setting gain to 2.0 will double the power of a light source. I have to believe that this isn't the same as just setting the power twice as high, but I don't know what it is.

In short, lowering any of these numbers will make your lightsource dimmer.

HOWEVER, LuxRender is VERY much based on the way light works in the real world. Consequently, your camera isn't just a viewport. It also has an exposure setting, tonemapping, white balance, and other things that will affect how bright the lights appear. If you watch animations done in LuxRender (like this one: https://www.youtube.com/watch?v=SVK7W0SXre4), many of them look like the exposure is being adjusted... because it is, automatically. LuxRender automatically chooses a sensible exposure level based on a number of factors, so you might have to tweak that to get the look you want.

Check these out:



Hope that helps!

  • $\begingroup$ Thank you Mattt. I am still grappling with the settings. It seems "GAIN" doesn't change the emission much ( I haven't noticed anything yet) the only thing I've noticed is when i set it to zero. then luxredner doesn't even run.which I think is logical because there is no light to trace. I think "GAIN" acts like a binary setting. it turns light either on or off. $\endgroup$
    – JUST16
    Nov 6, 2015 at 17:37
  • $\begingroup$ According to the documentation, that's not (or at least shouldn't be) the case. Gain is typically a relative setting, like the gain on a mic. If there's only one light in the scene, then there aren't any other lights for it to be "little brighter" than, so it'll just stay the same brightness. $\endgroup$
    – Matt
    Nov 6, 2015 at 18:25
  • $\begingroup$ LuxRender isn't the most intuitive renderer, but it's one of the fastest and most accurate renderers available. $\endgroup$
    – Matt
    Nov 6, 2015 at 18:26
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    $\begingroup$ That's exactly why I am trying to learn it. I was trying to do it through trial and error. I think I need to spend some time perusing the documentation and tutorials then I'll start over. Thank you. $\endgroup$
    – JUST16
    Nov 6, 2015 at 18:33

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