Q100197: How to modify the OCIO configuration file to adjust the colorspaces available in Katana's Monitor tab



The images displayed in the Monitor tab in Katana can be viewed with different display transformations applied. These transformations are defined in the OCIO configuration as device-specific look-up-tables (LUTs).

This article describes how to select different pre-defined LUTs and how to extend the list of available LUTs by adding a custom OCIO configuration to Katana.



Katana works internally in a linear colorspace. When scenes are Preview Rendered, they are rendered in scene-linear colorspace and previewed in the Monitor tab with a filmlook visualization to see the images as they would look on the final display device.

Each display device has a number of "views" which provide different ways to display the image. The view options that have been defined to apply different LUTs to the image can be found in the filmlook visualization dropdown, at the bottom of the Monitor tab.


By default, a limited number of these views are defined and active in the OCIO configuration. To add more options to this list, you can append to the “displays” section of the config.ocio file.



Manually, by customizing the OCIO configuration file

To achieve this, do the following:

  1. Locate the OCIO configuration file, which by default can be found in $KATANA_ROOT\etc\ocio\nuke-default.

  2. Create a folder called OCIO in a convenient location, for example your home folder, and copy the config.ocio file as well as the luts folder into it.

  3. Edit config.ocio, for example by adding more colorspaces defined as “views” to the “displays” section:
       - !<View> {name: None, colorspace: raw}
       - !<View> {name: sRGB, colorspace: sRGB}
       - !<View> {name: rec709, colorspace: rec709}
       - !<View> {name: rec1886, colorspace: Gamma2.4}
       - !<View> {name: AlexaV3LogC, colorspace: AlexaV3LogC}

  4. To use your custom OCIO configuration in your Katana session, set the OCIO environment variable to point to the config.ocio file in the OCIO folder, then launch Katana.

    How this environment variable is set will depend on how you launch Katana. For example:

    Open a terminal and enter

    export OCIO=home/OCIO/config.ocio

    Then launch Katana from the same terminal.

    Open a command prompt and enter

    set "OCIO=C:\Users\your.user\.katana\OCIO\config.ocio"

    Then launch Katana from the Command Prompt.

Programmatically, by using Python commands

It is also possible to customize the OCIO configuration without having to edit your config file by using Python code similar to this example:

from Katana import OCIO
cfg = OCIO.GetCurrentConfig()
cfg = cfg.createEditableCopy()

# New views can be added to the 'default' OCIO display
cfg.addDisplay('default', 'Gamma18', 'Gamma1.8')
cfg.addDisplay('default', 'Wibble', 'Panalog')

# Update the current config

If this code is placed in a $KATANA_RESOURCES/UIPlugins directory, it will run on start-up and append the set views to the default OCIO config.


For more information on OCIO color management, please see the Katana User Guide on Managing Color, the OpenColorIO standard and the OpenColorIO Python API.

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