Hello everyone, sorry but i’m a bit confused on the entire Gamma workflow <.<

I read a lot of stuff about how to work and setup a correct linear workflow and render it out into gamma 2.2 or 1.8 actually, 90% of people say windows is 1.8 and mac is 2.2.

Anyway my main problem is that some people say you just need to work without caring and in the end just plug a simple_tone_mapping shader to your camera, set 1.8 2.2 gamma and you’re done, other people say that you have to set first in XSI preferences under color management use gama 2.2 and switch on the preview on shaderballs etc, other people say that the gamma is calculated depending on your input texture and images (if any) so if you’re using textures there is a way in xsi to erase the color gamma value and overwrite it for final render re-assigning it to a 2.2 value..

Please can someone clarify this once for all ? <.< i’m getting used to work without touching anything and correct stuff with photoshop, but i really think its not the right way, my renders look a bit darker but i like them, if i just use those methods i said here the renders come out really bright and textures lose their saturation and color depth..

Thanks in advance to everyone..

Hi,

assuming that you understand what gamma correction generally does (and that’s the hard bit) http://en.wikipedia.org/wiki/Gamma_correction
Xsi gives us a handy tool to use.

go to preferences --> Display --> Color Management and turn on the check boxes (at least for “Render Regions").
This will display the render with the specified gamma correction.
The picture will appear brighter and especially the low values are raised.
Be careful as this is only for display purposes and the final render will still be a linearised gamma of 1 which you have to adjust in your favorite composeting application.

this is the workflow I do, and after having understood this, photorealistic renderings are almost magically easy to do.

good luck
christian

yep, in XSI LWF is easy job like blunte suggested. no magic voodoo steps like in 3ds max.

Using tone mapper will burn gamma to your image,
so I always render to at least 16-bit exr/tiff-s and then apply gamma in fusion/after effects. more non-destructive workflow.

The point of the gamma workflow is to remove the gamma from the textures so that the rendering takes place in linear space, and then add back the gamma to the final rendered images to see the result correctly. That’s all you need to know.

all of this is turned off by default. The user preference is the viewing part.

You also need to tell XSI what is the gamma of each each texture has been created in. If it’s an image in photoshop, it’s probably sRGB.

By default image clips are set to Linear, so no de-gamma of the image is taking place.  If it’s a photograph, this is wrong, because those images are sRGB and that needs to be removed so that the images become linear.

I dont get this… really

My preferences display color management have everything turned on, talking about preview on shaderballs, render regions and pass.

Also my profile source is set “From Gamma Values”
and the gamma values right under this is set to R G B - 2.2 each.
So i’m telling XSI that the gamma value i wanna use is 2.2.

Now, what this means ?
If i work on a scene from now on with those settings, all shaders + textures i use will be previewed in gamma 2.2, but will be rendered out not in gamma 2.2 ? I dont get this.

The point of the gamma workflow is to remove the gamma from the textures so that the rendering takes place in linear space, and then add back the gamma to the final rendered images to see the result correctly. That’s all you need to know.

all of this is turned off by default. The user preference is the viewing part.

This means that in theory the right workflow is to remove the gamma from the textures and add it later, but this as you say is turned off by default, so how i can turn it on ?

You also need to tell XSI what is the gamma of each each texture has been created in.

How can i tell XSI this ?

By default image clips are set to Linear, so no de-gamma of the image is taking place. 

But you just said that i have to de-gamma the textures and add it later, so if clips are set to linear how can i de-gamma them ?

yep, in XSI LWF is easy job like blunte suggested. no magic voodoo steps like in 3ds max.

Using tone mapper will burn gamma to your image,
so I always render to at least 16-bit exr/tiff-s and then apply gamma in fusion/after effects. more non-destructive workflow.

So you never ever use mia_photographic_exposure or tonemapping ? those are totally useless? since to my knowledge one of the use of the photographic exposure is to balance the brightness of portal light using saturation and gamma correction inside that node, how you would do this ?

Also if i set preferences to make me a preview in 2.2, then i add a mia_photographic_exposure and set to 2.2, that means my preview render will be totally overbright while my real render will be 2.2?

I guess i’m totally confused :D… sorry guys to waste your time :(

First of all, you should read WHY you should use LWF. Second of all, proper LWF would be:
-Gamma 2,2 in Display-Color Management
-sRGB for 99% of your textures in texture clip-Adjust-Color Profile (I think sRGB is by default)

AFAIK you can use and should use tone_mapper when dealing with sun&sky system.

If you set gamma to 2,2 in tone mapper you will apply gamma to image (so it will be visible when saved to e.g. JPG).

But I prefere to render out without gamma burned to image, to EXRs, and play with all tone-mapping/gamma stuff in composition software.

Here I made you simple scene expaining why LWF give alot more realistic images

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[quote=Maxsi77;20354]

You also need to tell XSI what is the gamma of each each texture has been created in.

How can i tell XSI this ?

This is a setting on the image clip.  In the Adjust tab, there is a Color Profile option, and by default it’s set to Linear.
This is the only bit missing from my post; Re-read it again for the answer to all the other questions.

Thanks a lot guys sorry for being annoying <.< i think i got it!

Oh, but i didn’t quite get it… at least i’m not sure.
What i’ve understood from wiki page and this thread is that 8bit images (jpg,tga,etc.)are better with sRGB and 16-32bit images (hdr,exr,etc) are better set to linear (in the clip>adjust) and then adjust gamma in fusion/after effects app, right?
If this is correct, then isn’t a bit easier to set the “color profile” in Preferences to “automatic”?
I’d realy apreciate if someone can enlight another butthead on the forum.

I thing you’re right it would be no difference. But if you set it to sRGB or linear you force it to do what you want and don’t have to trust the auto stuff doing it right.
Personally I like to see whats going on and hate the under the hood stuff, just makes error tracking a lot harder.

cheers
Christian

So guys, summarize it a bit.

First I HAVE TO set the image preferences *auto, sRGB, linear whatever) I set it to Auto, and overwrite it individually on the images PPG if it was a bump or HDR to linear, and if it’s a color texture, to sRGB. That’s correct, isn’t that? The question is to decide what images must be set to sGRB? Am I right if I suppose that not only photo based textures, but painted textures as well need to be set to sRGB? And am I right, if I suppose that value driving or masking textures gotta be set to linear?
And so on…

My problem is tht when I try to use color management my rendering falls apart, every color and luminance looks off…