Monitor Calibration

Successfully using colour management requires calibration of your display devices. The OCIO config defines several "displays", such as "Rec.1886 Rec.709 - Display" or "Rec.2100-PQ - Display". These are typically based on ITU or other standards and may be considered calibration aims for how to setup and calibrate a connected device.

More precisely, the display colour space in the OCIO config for a given display will define the exact math to get from the CIE colorimetry of the display-referred reference space to the display code values to be sent to the device. It may therefore be used to manually validate the calibration of a display. Using the Colour Transform tool in Custom mode allows sending values through a given display colour space, see Building Custom Colour Transforms.

Types of Monitors

To ensure that the displayed images are an accurate representation of the intended colours, your monitor must be calibrated. Calibration should be performed periodically because the monitor's response may drift over time.

With respect to calibration, there are two classes of computer monitors:

• Some high-end monitors (e.g., Eizo ColorEdge) have internal calibration circuitry. These monitors can be calibrated to emulate an aim specification for a given set of primaries and transfer function. You use the monitors built-in controls or the manufacturer's software to adjust these monitors to your desired aim.
• Other monitors must be calibrated externally using a third-party product to generate an ICC profile.

Using ICC Profiles

For computer monitors, the state of calibration is often defined via an ICC monitor profile. On macOS, you may enable Sync with OS in the Colour Management Preferences to use the ICC profile specified in your macOS Display System Settings. If you have more than one monitor, the application uses the one that is identified as the "Main Display".

When Sync with OS is enabled, OCIO is used to create a "virtual display" from your ICC profile. This results in a display being added to the in-memory OCIO config. If your config has a virtual_display defined, this will be used to populate the views for the new display. Otherwise, all shared views in the config will be added to the display unless those views are only used with HDR displays (i.e., display colour spaces with an encoding of 'hdr-video').

The display based on the ICC profile is not available in the View Transform tool and it is not added to the project's OCIO overrides, which means it is not included in an export of the OCIO config. This is because the ICC profile tends to vary between workstations and to update over time, so it would be inappropriate to bake a conversion to that display into images.

Using Apple XDR Displays

Apple's XDR displays may be considered high dynamic range monitors, capable of producing output above 1000 nits. Since ICC profiles are not suitable, Apple uses an alternative mechanism for dealing with HDR monitor calibration and defines a set of presets that are available in the macOS Display System Settings. It is recommended that for the most accurate results, you use the "HDR Video (P3-ST 2084)" preset. For the other presets, macOS adjusts the transfer function dynamically based on a number of factors. As a result, the standard transfer function aims are not followed exactly and this may give unreliable results.

In order to take advantage of the HDR capabilities of Apple XDR displays, you must use the Flame Family Setup application and enable "HDR Main Display" or "HDR Extended Display". This will lock the Display menu for your Graphics Monitor or Video Preview Device (based on which you enabled) to "ST2084-P3-D65 - Display". If you are not using one of the OCIO configs that ship with the application, you will need to ensure that that display is present and has the appropriate views defined. You may use the Flame Family default config as an example.