OpenColorIO (OCIO) is an open source color management project from Sony Pictures Imageworks.
It has been used on feature films like Alice in Wonderland, Cloudy With A Chance Of Meatballs, Spiderman(s), Surf's Up, and Watchmen.
Configuring OCIO:
Ramen comes with a very basic OCIO configuration. It's recommended that you download the latest color configurations from OCIO website (download the one that says v0.7v4) and use them instead.
There are currently 4 configs: spi-vfx, spi-anim, nuke-default and iff. Please check OCIO's website for more info. In case of doubt, nuke-default is usually a good choice.
The first time Ramen is executed, it will create a ramen1.0 directory in your home directory.
The easiest way of pointing Ramen to the new color configuration is to copy the config.ocio file and the luts folder to $HOME/ramen1.0/ocio.
A better option is to create an enviroment variable $OCIO and point it to the config you want to use. This way you can use the same configuration for all programs that use OpenColorIO.
It's rumored that future versions of Nuke will use OCIO.
In the following examples, the nuke-default config will be used.
Reading images:
Ramen works in linear color space. Normally, you want to convert all input images
to linear color space, do all processing and convert to your destination color space
when rendering the composition.
When reading images, select the input color space in the image_in node controls.
The image will be converted from the color space picked to linear.
Viewing images:
There are controls in the viewer to modify the way the images are displayed.
From left to right, they are display device, display transform, exposure and gamma.
It's important to note that processing is not affected in any way by these controls.
They only change the way images are displayed.
Converting between colorspaces and other ops:
There are a number of nodes related to color management:
- OCIO Colorspace converts between color spaces.
- OCIO File Transform applies luts and other transformations.
- Log to Linear converts between linear and log color spaces.
- CDL can import, export and apply standard CDL ( Colour Decision List) corrections.
Image output:
The last step is converting the images to the output color space when the composition
is rendered. This is done in the image_out node controls.
The correct color space depends on the output format and the output medium.
For EXR, HDR and floating point TIFF images, linear is the correct pick.
You'd use linear for images used as textures in 3d renderers for example.
For film output, use DPX or Cineon formats and a logarithmic color space.
Use sRGB for images to be displayed on a computer screen ( web, presentations, ...)
and video ( rec709) for HD video.
Use sRGB for images to be displayed on a computer screen ( web, presentations, ...)
and video ( rec709) for HD video.
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