2
$\begingroup$

First of all excuse me for my english, i try to explain better than i can.

I need to reproduce this real led lamp.

enter image description here

I have all the data of this lamp and the IES file.

Watt: 8W Lm: 880lm Lm/W: 110lm/W Kelvin/CRI: 3000K / >85 SDCM/L70 B10: < 3 / 50000

My problem is how to use the IES file and if i can reproduce a realistic lighting. When i import the IES, where i put it? The IES origin cannot stay inside the translucent or the light is lower. Can i scale it ? If i do larger or smaller, the light will be more or less strenght and if i import as it i must change all the scale of the room. The translucent part of the lamp is a glazed plastic, how realistic that can be reproduce? That obviously depend where the IES is. In alternative, with the data can i reproduce an emission surface? Or a blender light ( spot, area...)? I like to use this answer for all lamp i need to reproduce in the future. I know probably is a noob question. I try to search here ( and on Google ) something about that but i cannot find nothing. Thank you in advance

enter image description here

$\endgroup$
2
$\begingroup$
  • The first bit of info you need is that in Cycles, the emission unit of light is Irradiance (or Radiance Flux), it is in watts per square meter.

    You can read how that corresponds to Lux (in lumen) here: What kind of units does the Cycles emission strength use?

  • The second bit is that you can import IES files into Blender through this addon. It will create a light with rig that you can control to for example set direction of the lamp.

    This light uses mapping vectors and a custom Curve (that is imported from the IES file) to influence the strength of light based on emission direction:

    enter image description here

    The tricky bit is that the imported light type is Point, so you are getting only the emission of light, but not the light surface itself. You will have to fake the light's glass cover with translucent shader, that does not effect the light from the Point light - for camera ray it will be translucent, for light it must be completely transparent.

  • The third bit of puzzle is that you get the color from black body radiation node:

    enter image description here

    Note that in sRGB color space the white point is at 6500K, so you might want to compensate for that.

$\endgroup$
  • $\begingroup$ thank you Jerryno but...i had read and use previously all the information you give and the result is very poor. The light is very low and yellow. Using the IES scaling up, do a better result but i need something more accurate, for the lighting result. This means that the IES is not accurate probably. How can i use the data i have from the lamp in something i can use in Blender? $\endgroup$ – Fabrizio Mazzeo Apr 5 '17 at 12:19
  • $\begingroup$ @FabrizioMazzeo I am afraid it doesn't get much more "accurate" than this. Blender is still an artist-focused app, so you get usually the best result by eye-balling stuff. It would help if you could make the IES file public and a reference how it should look, then I could answer less generally. Might be also problem with how the data was measured, for example there is this database of IES files which works nicely with the plugin: mrcad.com/download-free-ies-lights $\endgroup$ – Jaroslav Jerryno Novotny Apr 5 '17 at 13:11
  • $\begingroup$ I try to put the link for IES but i don't have reputation for that but i have the image. Try here: reggiani.net/wp-content/plugins/icon-catalog/… $\endgroup$ – Fabrizio Mazzeo Apr 5 '17 at 14:10
  • $\begingroup$ @FabrizioMazzeo So I had look into the files, and there is not much - the files describe a uniform distribution all-around, like a simple point light. Imho there is no real gain using these files. The 3000K is warm light, which does not correspond to the reference - maybe because lots of white day-light present in those references. It might be worth a try also trying Filmic Blender for better view transform: github.com/sobotka/filmic-blender $\endgroup$ – Jaroslav Jerryno Novotny Apr 6 '17 at 12:05

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.