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About Real Lights for DAZStudio Iray

MartialMartial Posts: 425
in Daz Studio Discussion

Bonjour

I have bought this product  Real Lights for DAZStudio Iray because i was impressed by the pictures i see for illustrate it

But i have difficulty to have good result

Someone have some hints to how use it ?

specially for lighthing building inside and outside with night environment

thanks

Comments

  • greymouser69greymouser69 Posts: 501

    OK, first thing to understand is that these are not "lights" in the usual sense.  These are shaders that emit light and as such they will depend heavily on the geometry and/or uv/surfaces you apply them to.  I'm rendering a test of something I've been working on that only uses these for lighting and I will post it when my wimpy no cuda cores/cpu only system gets it good enough.  I will say that I am highly impressed with how they are working for me.

  • greymouser69greymouser69 Posts: 501
    edited April 2016

    Garage_testIray render set to scene only with the only light coming from the light fixtures where I converted the florescent tubes to 120 watt florescent on each fixture.  Very easy to use and works extremely well.

     

    Post edited by Chohole on
  • SpottedKittySpottedKitty Posts: 7,232

    One other gotcha, especially for indoor scenes. When you render in Iray, by default there's an Environment light with an HDRI map of a bright sunny day. The default exposure parameters are set up to match this. Most indoor lights aren't as bright as a sunny day, so you must pause and think about exposure levels before you render. And naturally, the same applies to outdoor scenes with cloudy/twilight/night lighting.

  • ToborTobor Posts: 2,300
    edited April 2016
    SpottedKitty said:

    One other gotcha, especially for indoor scenes. When you render in Iray, by default there's an Environment light with an HDRI map of a bright sunny day.

    Just a quick note. People here often say this, but it's not 100% accurate. If you go by the Sunny 16 rule, at ISO 100 and ~1/125s shutter, a bright sunny day should be f/16. Following the printed guides that used to come with medium speed film, you would see f/8 for hazy or partly cloudy. 

    This tends to bear out in Iray. If you light a scene only with a distant light, and set its output to about 10 or 11 lumens (equivalent to noonday sun -- approx 10-15 lumens/cm^2), you get an overexposed image at f/8. Change to f/11 or f/16 and it looks more natural.

    Post edited by Tobor on
  • ToborTobor Posts: 2,300

    BTW, the above works in 4.8, which I'm still using. Some other threads recently have suggested the behavior of distant lights has changed in 4.9. I don't have that version to test, but in any case, the Sunny 16 rule would still functionally apply, as it's based on EV units, which since the 50s have been used by camera and film makers to maintain consistency. EV 13 (ISO=100, shutter=1/125, f/8) has been defined as "Typical scene, cloudy bright (no shadows)." See Tabulated exposure values: https://en.wikipedia.org/wiki/Exposure_value

  • ToborTobor Posts: 2,300
    edited April 2016

    FWIW, in another thread, @Medzin confirms the behavior of distant lights is now different in 4.9. The lumens setting must now be significantly higher. Not having 4.9 installed on my machine, I don't know what real world metric the new values correspond to. It might also be bug, so the change is unintended.
     

    EDIT: It looks like they changed the scene units of distant lights from centimeters to meters. According to the example at http://www.daz3d.com/forums/discussion/comment/1107761/#Comment_1107761, if you enter values that used to work as cm^2, you need to multiply by 10000 for m^2.

    It could be a bug, and if it is, scenes you create or modify in the interim will break again when they fix it.

    Post edited by Tobor on
  • MartialMartial Posts: 425

    thanks everyone for your suggestions

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