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# Q100197: Changing and customizing colourspaces in the Monitor tab via the OCIO configuration file

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#### SUMMARY

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.

#### MORE INFORMATION

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

A number of different display devices are predefined in the default OCIO configuration used in Katana, and the list of available options can be found under Display > Display in the Monitor tab.

Display menu in the Monitor tab | Display menu in the overflow menu in the Monitor Tab

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.

SETUP

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 colourspaces defined as “views” to the “displays” section:
   displays:
   default:
   - !<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:
   Linux
   Open a terminal and enter:
   export OCIO=home/OCIO/config.ocio
   Then launch Katana from the same terminal.
   Windows
   Open a command prompt and enter:
   set OCIO=C:\your.user\.katana\OCIO\config.ocio
   Then launch Katana from the Command Prompt.

Programmatically, by using Python commands

It is also possible 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`

`OCIO.SetCurrentConfig(cfg)`

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

For more information on OCIO colour management, please see the Katana Online Help on Managing Colour, the OpenColorIO standard and the OpenColorIO Python API.