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FalconCrest
Posts: 1,409
Registered: ‎04-07-2012

Gamma Converting

31 Views, 25 Replies
11-28-2011 03:31 PM
How do I render the composition with Gamma 2.2 ? How can I convert any images that are Gamma 2.2 (sRGB) to linear Gamma ? I use EXR images which are linear gamma, so no worries as far as I know :smileyhappy:
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morazz
Posts: 897
Registered: ‎04-04-2007

Re: Gamma Converting

11-28-2011 03:59 PM in reply to: FalconCrest
when you bring your footage in, there is a options tab. You can convert it there, on import.
Mark Rasmussen
VFX - Supervisor | Compositor
Enigma|FX

TOXIK/Composite BLOG
http://enigmafx.ca/efxblog
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Distinguished Contributor
PiXeL_MoNKeY
Posts: 1,725
Registered: ‎04-14-2011

Re: Gamma Converting

11-28-2011 04:12 PM in reply to: FalconCrest
Use an sRGB Node before the output node. It appears that the output file format controls for Gamma don't work. NOTE: you should output to an 8bit format with the output node set to 8bit.

-Eric
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Distinguished Contributor
morazz
Posts: 897
Registered: ‎04-04-2007

Re: Gamma Converting

11-29-2011 01:25 PM in reply to: FalconCrest
Sorry man, I thought you where talking about import, but as Eric has said the output option is a bug, and effects all file formats. This should be fixed
Mark Rasmussen
VFX - Supervisor | Compositor
Enigma|FX

TOXIK/Composite BLOG
http://enigmafx.ca/efxblog
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Mentor
FalconCrest
Posts: 1,409
Registered: ‎04-07-2012

Re: Gamma Converting

11-29-2011 08:31 PM in reply to: FalconCrest
I placed my sRGB node before the output and it's set to 8 bit. Then following Mark R to view Gamma non-linear gamma in composite viewer and setting the exposure to 2.2 the composition does not look right at all. Then again that is only to view the composition at non-linear gamma in the player. What about rendering ?
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PiXeL_MoNKeY
Posts: 1,725
Registered: ‎04-14-2011

Re: Gamma Converting

11-30-2011 08:57 AM in reply to: FalconCrest
The sRGB node converts it to gamma 2.2, so you don't need the player modification as it is already showing gamma 2.2. So what you see in the output (without enabling the gamma in the player) is what it will render.

What you posted is causing double gamma conversion sRGB (gamma 2.2)+player (gamma 2.2).

-Eric
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Distinguished Contributor
morazz
Posts: 897
Registered: ‎04-04-2007

Re: Gamma Converting

11-30-2011 10:03 AM in reply to: FalconCrest
What Eric says is correct, on the output node or if you hit 7 for output view, you will get the double gamma, however, if you should be using node view or 6, then having your vLUT as you have done, will work fine, you just have to remember that the vLUT is not effecting the output, only the sRGB tool is. What I would suggest for a workflow is mute the sRGB until you do your final output, when you render turn it on and you will have the best of both worlds.

cheers
Mark Rasmussen
VFX - Supervisor | Compositor
Enigma|FX

TOXIK/Composite BLOG
http://enigmafx.ca/efxblog
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Mentor
FalconCrest
Posts: 1,409
Registered: ‎04-07-2012

Re: Gamma Converting

11-30-2011 08:11 PM in reply to: FalconCrest
The sRGB node is before the output. When I remove the sRGB node, the output preview looks fine. When I place the sRGB node before the output things don't look right in the preview viewport. Eric mentioned that is because there is double gamma happening.

Since sRGB is converting any images in my composition to linear gamma (I hope it's excluding EXR files which are linear to begin with?), how do I setup the player view to Gamma 2.2 ?

The overall goal is to keep non-linear images (EXR etc) linear, strip Gamma 2.2 or sRGB images of their non-linear gamma then rendering and previewing the composition as Gamma 2.2 so far from the replies I haven't quite understood or it's not working.
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Distinguished Contributor
morazz
Posts: 897
Registered: ‎04-04-2007

Re: Gamma Converting

12-01-2011 12:09 AM in reply to: FalconCrest
Here are the steps,
1. Load exr footage, it is linear light
1a. Load srgb/gamma 2.2 material, in the image loader you can remove 2.2/srgb so you now have a linear light image.
2. Do your work as you normally do.
3. Prior to the output node put a srgb/gamma 2.2 node to add back gamma curve
4. Render out.

Note1. The output option for gamma curve options is not working.
Note 2. When working, make sure the gamma 2.2/srgb node is muted or off so it does not display a double gamma in the viewport. The output will always be correct but the viewport will not show you the correct result if you leave it on. When muted the srgb vlut that you apply in the passthrough for the viewport will show it as a srgb gamma, but you are actually working in linear light.

Correct me if I am wrong but did I not do a tip on this topic

Cheers
Mark Rasmussen
VFX - Supervisor | Compositor
Enigma|FX

TOXIK/Composite BLOG
http://enigmafx.ca/efxblog
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Mentor
FalconCrest
Posts: 1,409
Registered: ‎04-07-2012

Re: Gamma Converting

12-01-2011 04:24 PM in reply to: morazz
1a. Load srgb/gamma 2.2 material, in the image loader you can remove 2.2/srgb so you now have a linear light image.


MarkR - When you say the image loader do you mean the image import tab ?

When muted the srgb vlut that you apply in the passthrough for the viewport will show it as a srgb gamma, but you are actually working in linear light.

I don't understand what you mean ?....
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