IES lights with VRay - help

[Klavix]

This is my first time trying to use IES lights, but it certainly isnt going well - I cannot make them work at all. Must be something wrong in the renders settings perhaps or something.

 

I have one Vray light in my interior scene, and I just made free light - vray shadows, photometric web and used a IES light I downloaded from LL. Render shows absolutely nothing. Render settings: irridiancemap, light cache, Adabtive DMC, colormapping expotential. Before this I tried Vray's own IES lights but the result was same.

 

Help would be greatly appreciated.

 

I attached images, no much materials yet, just trying to make the darn lights work properly

[Crazy Homeless Guy]

IES lights are not tuned to work with exposure on a physical camera. So you either need to crank them way up to work with exposure on a physical camera, or turn off the exposure and tweak them slightly.

[Thablanch]

IES lights are not tuned to work with exposure on a physical camera. So you either need to crank them way up to work with exposure on a physical camera, or turn off the exposure and tweak them slightly.

 

I would say the exact opposite, they work perfectly with the Vray camera exposure. The default Camera exposure of course does not work with interiors..

They emmit precise lumens, just as the Vray sun is

[btee]

I'd have to agree with crazy homeless guy here. I usually have to increase the intensity a LOT to get the right amount of light.

[Ismael]

I agree with Thablanch.

[Crazy Homeless Guy]

I don't beleive it is that simple. I don't fully understand the settings in IES files, but I imagine that they may vary by country, and whether or not they are prepped in Lumens or Candelas. I am only guessing this, because when you place some IES's with no exposure they are good, and when you place others, they are still to dark. The difference is greater than what the difference would be in real life.

 

But I digress, ....attached is the ubiquitous mr16 that is in the nice IES collection that every CG artist loves, and ever interior designer hates.

 

Look at the image on the left. I have exposure turned off on that image. Look at the image on the right, I have exposure turned on in that image.

 

The light strength is the same in both. The only difference is that I had to spend time tweaking the f-stop, shutter speed, and ISO setting in the exposure version. Meaning I spent more time on it, and had to do more test renders.

 

I prefer to start with no exposure on interiors because there are fewer controls that need adjusting. You can certainly do it both ways though. If I am not completely happy with the raw results I am getting, then I may use exposure to fine tune my image before moving to post production.

 

But I think we agree that IES lamp files and sun intensities don't play nicely together.

 

Take from it what you will, but to me IES files are all over the place. I would not assume that there intensity levels are accurate and designed to be used with camera exposure.

 

That said, you should probably never trust one to be close that was not downloaded directly from the manufacturers website.

Edited March 7, 2011 by Crazy Homeless Guy

[CliveG]

Perhaps the answer may be to do with scale for IES lights.... is there any imbedded scale in an IES file and if so what is it (and is it fixed and standard).... because some of you (USA) are still in the dark ages using feet and inches, some of us progressives are using MM and some other weirdo's use CM's.

 

Perhaps this may have an effect more than the Physicalcamera / std Camera exposure?

 

I'm just throwing that in there for debate by the brains out there....

[Thablanch]

Whatever you work in, mm, cm or inches, makes no difference. Vray and 3dsMax are reading both perfectly.

If you download an .ies from a manufacturer ( erco, ge, sylvania.....) the values in there are the good values.. Just like when you are entering a room, your eye ajusts. In this case the camera ajusts.

 

The film iso for an interior can not be 100. Take your camera or cell phone, and take a picture tonight home, and look at the Fstop/shutter/iso values. You will see it is nothing like the defaut Vray camera. The Vray camera comes in perfect for an exterior shoot, so if you do an interior, the camera, as your eye, has to ajust.

 

Also depending the numbers of lights you have in there... I'm now working a project with 1500+ ies lights, it is way faster to ajust the camera to some real life values of the .ies instead of fooling around with lights to have a nice image.

 

the power of Vray ies is in lumens:

 

http://www.spot3d.com/vray/help/150SP1/vrayieslight_params.htm

 

(Just as a reference, a normal 100w incandescent lightbulb is around 1150 lumens, as a typical MR16 halogen is somewhere around 900. )

[luisoosiul]

Hi. The IES files are an standard around the world. They are used to illumination calculations of illumination programs. You don't need tune the IES file to work properly with it. You only have to setting the physical camera like you do in the reality.

Try this camera setting:

aperture: f8

speed: 1/8 s

ISO 125

or an equivalent setting. This settings is quite equivalent to work without camera exposition. Respect to work with sun and IES files, you have the same problem than in the reality when you take an interior photograph. You can render two images with two different expositions (one for the sun and one for the IES files), and then blend them or you can setting the sun to work properly with the IES files. But is not a problem, simply that the sun intensity is very much more strong than the usual lamps. Equal than the reality.

Also try to work with LWF settings. It is helpfull.

Cheers.