I would just like to take a look at all the nodes and setup in the scene to have a better idea of what is going on.  As THNKR said above, the Surface Shader should not be showing any shading so I’m a little confused.  I’d like to make sure I have all the info.

Just remove anything from the Maya project that you don’t want to upload, and ZIP the project folder.  Reply to this topic and attach the ZIP in the reply.

See this if thread if you have trouble attaching:

http://area.autodesk.com/for...-area-ate-my-attachments/

Thanks!

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

I have attached the file

And below is the screen capture of those nodes,

1) the connection of mia_exposure simple to the physical sun shader & my camera

2) the difference setting of physical sun shader’s mia_exposure_simple and it’s default.

I didn’t tweak the surface shader setting

	Attachment
1_sailing__copy.zip

It appears that the surface shader is affected by the exposure control.  I noticed in your scene, the “surfaceShader1” material did not have a gammaCorrect node between the file image and the Out Color.  I added a gammaCorrect node and set to .455, .455, .455 and I set the Color Gain of the file image to V = 2.0 and it looks fairly close to the source image.

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

Valen Wagner 24 May 2011 10:46 PM

It appears that the surface shader is affected by the exposure control.  I noticed in your scene, the “surfaceShader1” material did not have a gammaCorrect node between the file image and the Out Color.  I added a gammaCorrect node and set to .455, .455, .455 and I set the Color Gain of the file image to V = 2.0 and it looks fairly close to the source image.

Yep, thanks, i forgot to add the gamma correction to this version, Just like earlier we discussed, color gain v=2.0 is ideal case.
Somehow it’s affecting by the exposure control by the physical sun & sky, so i guess we have no ways to tweak it right? So could it be consider a bug if that’s the case? Maybe we can feedback to autodesk.

Thanks alot of trying out my project.

I don’t think its a bug.  I think its just a result of the JPG image your using having a color value range of 0 to 1.  When you start using Sun & Sky shaders and Exposure Control the color range is increased a lot.  It is necessary to “amplify” your JPG image so that it enters into color range of the Suny & Sky and Exposure Control.

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

Valen Wagner 25 May 2011 10:21 AM

I don’t think its a bug.  I think its just a result of the JPG image your using having a color value range of 0 to 1.  When you start using Sun & Sky shaders and Exposure Control the color range is increased a lot.  It is necessary to “amplify” your JPG image so that it enters into color range of the Suny & Sky and Exposure Control.

Hi Valen,

What do you mean by “amplify” in this case? Is it means that jpg colour range has increase much more but with the exposure to dim it so it wont over exposure it? (since the sun & sky light is very strong) I don’t quite understand. Could you explain a little more? Thanks.

Just a side question, i read your post, I thought I could use other format, such as tiff, so I tried 2 methods,

1st method) I convert a raw file to tif, and it still have to convert the color gain value to 2.0 (with gamma node)

2nd method), from jpg to tif, it encountered an error:
Error: (Mayatomr.Output) : while defining texture “file4:tex”: failed to open texture file D:/Projects/Maya/1_sailing - Copy/sourceimages/IMG_71602.tif

Why is it have such error? it it because 8bit jpg even convert to tiff, though it allow more than 8bits of data but it has only 8bits of color in that file since it’s converted jpg?

What do you mean by “amplify” in this case? Is it means that jpg colour range has increase much more but with the exposure to dim it so it wont over exposure it? (since the sun & sky light is very strong) I don’t quite understand. Could you explain a little more? Thanks.

When I said “amplify” I was referring to increasing the “V” value.  The gamma correct node sort of brightens or darkens an image, but what it really does is adjust color values in-between 0 and 1.  0 stays at 0 and 1 stays at 1.  But the gamma correct node will bring up or down the mid-range color values so that the image does not appear washed out when exposure control is used.

Here is a helpful video that better explains gamma:

http://vimeo.com/8119194

Just a side question, i read your post, I thought I could use other format, such as tiff, so I tried 2 methods

Any format, other than an HDR image, will have color values going from 0 to 1 only. So you will have this problem no matter what with this particular image you’re using.

2nd method), from jpg to tif, it encountered an error:
Error: (Mayatomr.Output) : while defining texture “file4:tex”: failed to open texture file D:/Projects/Maya/1_sailing - Copy/sourceimages/IMG_71602.tif

I’m not too familiar with this, but I seem to recall mental ray in Maya having a problem with certain compression formats for TIFF images.  Try saving it as a uncompressed tiff, if possible.  Otherwise, I suggest you post a new topic to deal with it.

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

Thanks n8skow for the info ^^

Yep, but if we stick with the linear workflow, i guess we could only add one gamma correction node, 0.455 then add another gamma correction node with value to help or like the method you suggestion color gain value to 2.0

From you what you said, I actually think maybe it’s because physical sun & sky created, the calculation of color space changes. but the surface shader node’s colour also change (somehow calculation didn’t go the “right” way) Please correct me if I’m wrong.

Thanks for all the advice, I really appreciate it.

It would be nice if the exposure controls were able to pass the Surface Shader without affecting it so that it still looked “normal” after rendering, but as of today it requires these extra steps to bring up its color values.  Maybe Maya 2013…

3ds Max 2013, Maya 2013
Windows 7 Ultimate 64 Bit
Core i7, 12GB RAM
Nvidia Quadro FX 3700 (Driver 267.17)

I’ve just had the same problem.

I found this blog that explains it very well.

http://3dlight.blogspot.com/2008/09/linear-workflow-for-maya-mental-ray.html

Basically you have to tell Mental ray that you’re working in linear space.  You do this under the frame buffer tab found here Render settings/Quality/Framebuffer.

Set it to RGBA (float) 4x32bit and change the gamma setting to .45

That will tell Mental Ray to remove any embedded gamma from your images.

Hope that helped?

All the best

Peter