linear workflow

[dkreset]

interesting, that's opposite of whatever I read from before... as far as my understanding goes photoshop codes the images with a 2.2 gamma so that they will appear properly on our monitors because our monitors' color space is technically 2.2 if we don't fiddle around with it.

So you mean Octane already renders in 2.2 by default? In this case I wouldn't need any color adjustments to my textures if photoshop does in fact code the images with 2.2 gamma right? I would need to only tweak the gamma settings if the images are .454 to start with?

Sorry if my questions are ridiculous because this isn't how I understood linear workflow at all for Vray and mentalray

[roeland]

The monitor itself applies a gamma correction of 2.2 (let's assume the monitor uses the sRGB color space). This is called the display gamma. So if a program sends [128 128 128] the monitor doesn't display 50% but 22% brightness. Images are usually encoded in sRGB so they can be sent to the monitor unmodified, to encode an image that way from linear image data the encoder must apply the inverse gamma correction of .45455.

Photoshop (and other image editors) usually ignore all of this and don't do any gamma corrections. I made another post about this a while ago. When editing pictures you don't see much artifacts because of this but sometimes it will cause problems (e.g. if you blur a small highlight the result will be too dark).

Octane always works in linear space. If a renderer uses anything else the rendered images will look completely wrong.

Any images coming in have to be converted back to linear space. Octane asks for the gamma correction applied to the image data after loading it (the inverse of the encoder gamma, usually equal to the display gamma, 2.2. Some programs ask the encoder gamma instead, which is .45455).

And before writing out a PNG image or displaying an image it will apply a gamma correction of .45455 to compensate for the display gamma. In the tone mapping settings if you disable the film response curve you tell Octane the display gamma of your monitor, 2.2.

--
Roeland

[face]

What is about the imager?
How we can get a linear result.
Only change the camera reponse curve to linear isn´t enough. To add a gamma of 2.2 looks to flat.
If i set then the exposure to 2.2, it looks nearly perfect.
Or it´s better to set the exposure/gamma to a monitor 1.6?

face

EDIT:
Ok, 1.6 should be for old crt monitors...

[tomas_p]

Hi octaners...
Color Management is a pretty complicated thing. But luckily this is only a part of the whole problem.
I have read that for the different systems are different gamma correction.
I use for pictures with 8 bits per chanel from photoshop (sometimes more to) gama corection 1.8 and for HDRi I made direct from RAW gama corection 1.0 (this is without corection).

If you are not sure which gama is good for your computer or current picture, trie 1,0; 1,6; 1,8; 2,2 and one wil be relative OK.

Regards
Tomas

[dkreset]

Thanks for the response guys! I'm starting to understand this much better... just a few more questions left. When you guys talk about the gamma correction, you're talking about the actual gamma slider for the "image" node after you import a texture, correct? Secondly, when you say film response curve under tone mapping settings, do you mean the camera response? If not where is this tone mapping section with the film response curve cuz I looked all over for it ...

sorry for the noob questions! relatively new to linear work flow Thanks again guys!

[fovito]

So Octane simply ignores ICC profiles and assumes an unmanaged workflow based on sRGB default values?