View Full Version : Vray and profiles..

07 July 2011, 06:56 PM
Hello. I am in need of help and have a few questions regarding Vray in Maya...

1.When I render to EXR format the render is very bright ( looks as if I have the SRGB button pressed in the Vray Frame buffer).

Why is this and how do I convert it to the proper color profile in after effect or photoshop. Photoshop just tells me it doesn't support embedded profiles?

2.When rendering to formats like tga I always get the same image as if the SRGB is NOT enabled (renders are dark) in the Vray frame buffer. What accounts for the difference?

thanks for the help.. I am so confused

08 August 2011, 07:24 AM
I guess the difference is that Photoshop assumes that OpenEXR files contain data in linear space, and so they need to be converted to sRGB space in order to work with them in Photoshop. With other file formats, it is the reverse - the assumption is that they already contain sRGB colors and so no further conversion is necessary.

Best regards,

08 August 2011, 12:33 AM
Awesome answer and perfectly worded..

How can I assign the correct profiles myself? What is the best way to do this in photoshop?

08 August 2011, 04:49 PM
add an exposure adjustment layer and set the gamma to .454 (or just set it in an Exposure adjustment)

If it's too dark, do the inverse (2.2)

08 August 2011, 08:33 PM
I think it' better to just setup VRay, so it works in "linear" space - what you see in your render view is the same as what you'll see in a compositing app like Nuke for example( can't tell about AE though). Otherwise if you raise your gamma for a dark image there will be a lot of noise from the undersampling in the shadows. I can't tell if this is the 100% right way to do it, but this is how I did that:
color mapping - linear
gamma 2.2
adaptation only - on
linear workflow - on
convert to sRGB for render view - on
image format - exr

08 August 2011, 11:19 PM
if you want all that done in one click, that's what the LWFMe button in my V-Ray Tuner script does:

08 August 2011, 03:16 AM

Thanks so much. I've got a working Linear workflow now with the "exposure" layer being the missing part.

I am also using your mel script to control Vray..I like it alot.

I still don't understand why the gamma is so different between 8 bit & 32 Bit images of the same scene but I guess I don't really need to since everything is working.

I render to 32 bit EXR and the use the exposure layer and I can control my image that way.


08 August 2011, 03:39 AM
BTW, is there a way (or a need) to gamma correct the color picker when creating shaders? I often see this stressed in Mental Ray tutorials. Obviously it is easy to adjust the color but I spend too much time setting up renders and anything I can do to streamline the process helps alot.

08 August 2011, 04:47 AM
If you have the Linear Workflow toggled on, Vray linearizes the colour swatches automatically.

There are times when you want to do a manually done gamma correction in Vray - if you have SSS shaders, they don't respond correctly with the automatic LWF so you need to correct swatches and images and disable LWF. There is a gamma correct script in a vray tuner dropdown for those times. Hit LWFMe and then turn off the LWF checkbox and then when you gamma correct nodes, it will be set up for a manual linear workflow.

08 August 2011, 05:11 AM
What color profile is everyone using once the exr is inside Photoshop? Usually it'll ask to embed a color profile, are people here just assigning the monitor's profile or the basic sRGB profile?

I'm not sure what would be the best option?

08 August 2011, 05:53 AM
Photoshop automatically recognizes linear sRGB profiles here. What version are you using?

08 August 2011, 03:07 AM
when photoshop asks for the profile remember it will not be saved with it if you keep it 32 bit (it is just for temporary viewing)

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