how to use photometric lights in vray?

[Tim Saunders]

I know your frustration Ed. Strange problem with the units however. I assume the intensity of the lights will remain the same no matter what units you are using as long as they are real world (feet or meters).

 

Travis,

Thanks for such an in-depth explanation. Your test renders show the difference. It still looks a little dim for 4-75watt bulbs in a room that small. The only thing you didn't mention is the color mapping settings you used. I guess downloading your scene will answer that. It still looks like you are guessing a bit in the gamma adjusting. It just seems like there has got to be a way to do this without guessing on anything.

[Crazy Homeless Guy]

I know your frustration Ed. Strange problem with the units however. I assume the intensity of the lights will remain the same no matter what units you are using as long as they are real world (feet or meters).

 

Travis,

Thanks for such an in-depth explanation. Your test renders show the difference. It still looks a little dim for 4-75watt bulbs in a room that small. The only thing you didn't mention is the color mapping settings you used. I guess downloading your scene will answer that. It still looks like you are guessing a bit in the gamma adjusting. It just seems like there has got to be a way to do this without guessing on anything.

 

the gamma adjustment should be mathmetical, except i can not remember if my monitor is calibrated to a 2.1 or a 2.2 gamma.

 

i am also wondering.... i used a vray physical camera for the view. this might create problems becausse i manually adjust the f-stops, shutter spped, and ISO. setting them wrong could result in a poorly lit image. maybe i will try and render with a standard camera and see how the results turn out.

 

....but yes, i agree that the image still seems to dark.

[Guest nazcaLine]

waht i learned from a tutorial is that when using ies with vray, besides using inches or centimeters in the system units, is thet you must increment considerably the Diffuse multiplier of the Light panel or the System rollout. when you render and get a black frame, increment that value to approx.200-800 (depending on the scene). only then you can see the photons.

[Sawyer]

On Chris' vray DVD for interiors he talks about putting the mult value for IES lights to 400%. Seems to work not sure why.

[Tim Saunders]

Yeah, typing in 400 in the multiplier% deffinately helps. It still looks dimm. Is is safe to say we can use that as an accurate lighting analysis for the lighting consultant? I just don't want to end up saying we need 2x as much light in a space because my rendering was innacurate.

[DaveP]

Hi Tim, we have just had the same problem, we use mm for all our units, we tried upping the intensity of light source, that kind of worked but threw to much colour bleed onto the ceiling. We ended up adding a Vray light to the scene, which help with GI and reduced the colour bleed but as you discussed this is not ideal. Did you resolve the problem? We are currently looking at Linear space and changing the units.

 

regards

DaveP

[Tim Saunders]

I never got it resolved. For that matter, I don't use ies lights any more at all. I think there may be a conflict between vray 1.5 and ies lights. they take WAY longer to render now. I'm pissed because now I can't even use them for wall washing effects (which I love). They are just taking way too long to render. Because of that, I stopped experimenting with them all together. My work load is too busy right now.

 

Can anyone confirm if there is a confliction between vray 1.5 and ies lights?

[Kalimero]

the only photometric that seems to be posing real problems to me is the area one.anyone else the same?

[YOHKOH]

I had the darkness problem and have managed to solve it using the "crazy homeless guy" method.

 

I work in mm and i don't think it makes any difference which unit you use as long as they are not the max default units. i.e. You can use mm, inches, cm, meters etc.

 

The main setting to look out for is tha gamma

 

1. Use a vray physical camera and change the settings using the exposure calculator below.

 

http://www.robert-barrett.com/photo/exposure_calculator.html

 

2. I set the colour mapping to exponential, as this stops the burn out around the lights experienced with linear multiply.

The setting to change is the gamma, to 2.2 in my case, but it's worth experimenting.

I dont touch the physical scale settings and have the exposure control set to none in the environment roll out.

 

Also i turn off enable gamm/ Lut Correction in the Preferences/ Gamma Lut settings tab Found in the customise menu.

 

This works great for me

 

1st image using a standard camera and gamma at 1.0

2nd image using a standard camera and gamma at 2.2

 

[Ismael]

What I find that the Travis scene should 'look like' is: