Describing Reference Display Characteristics and Reference Viewing Environments
Both the display and the viewing environment are critically important to the color perception that some colorimetry creates. We have to be able to combine content which was mastered on different displays in different viewing environments and have that combined image create the same (or at least a similar) perception on the display and current viewing environment of the user.
As with other image description properties so far, some standards/recommendations/etc define their reference display and reference viewing environment, some reference them from other documents and some are defined very loosely.
There are no CICP code points, or other enumerations, for those two properties.
Should we invent our own? Should we only support explicitly setting all data of the properties instead of relying on code points? Can we talk to the CICP authors?
It is unclear which data exactly the two properties should consist of.
Some data is pretty obvious for the display: minimum luminance, maximum luminance. Reflectance/glare seems to be common as well. HDR displays also have more luminance related parameters, such as the maximum luminance under certain conditions (e.g. when displaying white on 100%, 10%, ... of the screen).
For the viewing environment the ambient luminance, the background luminance and color, how many degrees of the viewing field is covered by the display can all be useful.
It is unclear how to map the definitions in the standards to our own definition.
Especially the older standards have a very loose definition of the reference display and viewing environment which makes mapping them to the explicit definition tricky.
Adjusting the display to the viewing environment
The end user often has controls to adjust the luminance of the display to counteract the changing viewing environment. Sometimes the display itself does the adjustment, and some systems give user space access to sensors and brightness controls. This means that while both the viewing environment and the display characteristics of the user change, the resulting color perception stays somewhat constant in most situations.