VFB and gamma

[QuakeMarine1]

I am not sure I understand corretly the way of VFB

I render a scene without VFB and MFB show me the image as I as need - it also save the file correct
if I now render the same scene and just switch to VFB (save to exr) I see the corect image but it save the exr to disk much more brighten - the image save as the sRGB show me

the 3dsmax gamma and lut is diabled and the colormapping gamma of Vray is gamma 1.0
linear workflow off (not different if on)
the image is still gamma+2.2 burned in

were that gamma come from?
so what options do I have to save the image from VFB as MFB do ?

thx

[RErender]

EXR's display the gamma by default, some programs deal with it correctly like Fusion for instance, others do not, like combustion and photoshop, it's not really "burnt" in though since you are dealing with float or half float you can add the inverse gamma to the image without loss.

[Intuition]

Actually fusion defaults to displaying a 1.0 gamma space.

You have to tell it to display in 2.2 gamma in the settings next to LUT. Even when set to 2.2 though it will not save in the baked 2.2 gamma curve (output to non-floating point image type) unless you have a CC node somewhere down the line before the save node that adds back in the gamma.

If you open up the file in photoshop CS3 it will display the gamma curve at 2.2. This is the correct way depending on how you use photoshop. If you have a monitor that is set to display in 2.2, which most are, then when opened in photoshop it will show you what your image really was lit like. If it looks foggy and blown out then you probably lit the scene in 1.0 gamma space and the frame buffer is showing you 1.0 gamma space but when you open it in true 2.2 gamma space it looks foggy, grey and blown out with little contrast.

The Vray frame buffer has a sRGB button you can turn on to show you what your image will look like in 2.2 gamma space.

Now if you light your scene in the 1.0 gamma space viewed on a monitor that is displaying in 2.2 and feel that is the correct way you wanted the image to look then you will want the image to bake in the 1.0 gamma space which is what is happening with the max frame buffer.

If you render your image in the vray frame buffer with the gamma set to 2.2 in the color management and it looks correct before your press the sRGB button on and then it looks all gray and foggy when you press the sRGB button then one of three things are happening.

1. You aren't really utilizing the extra color space that a gamma 2.2 workflow allows because of a misunderstanding of how it all works. The whole reason for getting into a gamma 2.2 workflow is so that you can utilile the 32bit float color space and not have super black areas slamming right up against blown out whites when trying to light your scenes evenly (well at least one of the many reasons).

OR

2. You may have all the setting right but you may not have "dont affect colors (adaptation only)" checkbox turned on. What this does is allow the 32bit float render to be viewed correctly with the sRGB button turned on but the actual render will save to an EXR correctly without the 2.2 gamma baked in at the 1.0 curve setting. This will mean that when viewed in photoshop CS3 or newer it should open up correctly. If you are not saving to a 32bit float image type and just want to flatten the 32 bit out to a TGA or JPG then you will want to have adaptation only turned off so that when you save your image it will burn in the 2.2 or 1.0, whichever setting you had in the color management.

If you have the gamma 2.2 workflow working correctly your image should be too dark or at least darker then desired until the sRGB button is pressed in the VFB in which it will look correct. Gamma 2.2 workflow is weird to understand at first but gives you much more range in your lighting/rendering.

Its is really useful for having much more midtones/brightness range especially in apps like flame nuke and fusion which can utilize the gamma curve really nicely.

Read more on this here. He specifically talks about the different problems with gamma 1.0 vs 2.2 in many aspects like the monitor, the color shading surfacing, the max vs vray frame buffers, as well as file outputs baking different gamma spaces.

http://www.aversis.be/tutorials/vray...l_gamma_01.htm

The linear workflow button is only peeling out the gamma from your images and surfaces IF you are lighting in a different gamma then 1.0. Otherwise it will leave them alone, or I mean do nothing since there is nothing to adjust to/from.

----edit----

Forgot.... Quakemarine, since you did render to EXR and if you saved with 32bit floating point... you should be able to take the image into Photoshop and do an " Image> adjustment > levels " or Ctrl+L and then use the center intergeter (1.00) and enter (0.4545) to get the correct display of your image. This is essentially the reverse of lighting in 2.2 gamma and saving to 1.0 gamma for display in 2.2.

It is lighting in 1.0 gamma, displaying 1.0 gamma in 2.2 gamma and returning the curve to 1.0.