Colors are washed out with mental ray sun/sky

When using het sun/Sky system in mental ray, it adds a mia_exposure  node to the camera.
By default the "Gamma" Value is 2.2, thus the change of color values of your render.
This can be fixed by using one of these two approaches depending on the scene.

1. Per file texture 
   Add a Gamma correct node between the texture and the Shader
   Change the Gamma value to (1 / 2.2 )= 0.455
2. Per Scene
   In the render settings, under the “Quality” tab > framebuffer section change the value to .455
   Under the mia_exposure node, change the Gamma value to 1.0

Comments

[KM]

Do you know which is the preffered method for this solution?

I've noticed there is a differences between the framebuffer mode vs the gamma correct method. framebuffer looks more natural but there are a lot of people who like the other method, it's confusing.

Also, Maya swatches need to be adjusted with gammaCorrect nodes using the frambuffer .455 method and also file textures with Elliptical filtering used.

[Ash Aiad]

It depends on the scene and it’s components.
For example, I would use method 1, if my Shader has color values (not textures)

As for the other note, its under the developments consideration.
Cheers
Ash

[dwilks]

u should be aware that using the frame buffer method you will get bad results in extreme shadowed areas. The values of the textures drop off to black resulting in graininess/incorrect result. safest method is to use a gamma node. This can be cumbersome but its reliable.

[KM]

Yes, but is the light not natural using method 1?

I mean if you have a material at 0.5 grey it would scatter exactly half the light hitting it, however when you apply a gamma correct node to it, it will not scatter exactly the light anymore but rather a smaller portion. Using a gamma correct node would not be accurate if the color was supposed to be a 50% grey material in terms of light scattering when using a gamma correct node.

[Ryan]

Are mental ray/Maya shaders not linear by default if just using color values?

If I create a linear texture in Photoshop at gamma 1.0, is any of this correction necessary?

[Roy Achkar]

i was a big fan of method 1 i found out that gamma correct nodes are affecting the FG solution in a way thy are not supposed to.
So KM is completly right.
here's some illustration for this issue:
http://forums.cgsociety.org/showthread.php?f=87&t=764761&page=5&pp=15

[Smokedogg]

KM- I was wondering this same thing. Wondering if you have found an answer and if so can you let me know. I have my textures in photoshop and converted them to 32 bit and saved as .exr. (meaning they should now be in a linear color space) Therefore, I dont believe any extra gamma correct nodes are necessary. (please correct me if im wrong) I also think when ready to render out final images, the framebuffer change to 4 x 32 float with the default gamma of 1.0. Or is it 0.45? Also, get rid of any lens exposures cause you do that in post. Can anyone please confirm that this is the correct workflow?
Thank you.

[generic viagra]

How do you make realistic grass in Maya using Mental Ray?
I was using a grass paintbrush in Maya 2008, but I guess that Mental Ray doesn't recognize it because when i render out a scene the grass doesn't show up. Does anybody know what's the best way to make grass in maya using mental ray?

[Juan]

Maya2012, in the camera, in the mia_exposure node, change GAIN and GAMMA to 1.0
;)