Intentional Color Corrections Planned for Display in Ambient Light

Started 2 months ago | Discussions thread
Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 15,734
Museum lighting

Actually, museum lighting led to some knowledge of the effects of human vision that are addressed in color appearance models.

The idea behind a color appearance model is understanding how color vision changes when not in ordinary conditions. Pretty much all of our cameras and software assume good viewing conditions, where everything is well lit, with a spectrally good light source of a particular white point, and color samples are fairly large and surrounded by neutrals. The standard RGB color models we use all assume this, and we rarely have problems when viewing colors in broad daylight and bright interiors. But we have problems when conditions are far from normal.

Museum curators guessed that artworks would look best in the same kind of  lighting that the artist used to make them. So a plein-air painting would look best in broad sunlight (a color temperature of maybe 5500 kelvin) while a studio painting may look best with lighting with high color temperature approximating skylight (7000 K or higher). But you can’t use bright lighting as that may fade the artworks, so they used dim bulbs. But the results were poor: the dim lighting looked too intensely blue.

As it turns out, as brightness decreases, the range of color temperatures that the eye will perceive as “white” narrows substantially.  If the lighting is as bright or brighter than a well lit office, then you can get away with a wide range of color temperatures which the eye will perceive as white, at least after adaptation. But once you get to a significantly dimmer living room at night, you’ll need much warmer lighting to make things look white. It shouldn’t be too surprising that domestic bulbs are about 2700K while office bulbs are higher, like 5000K.

This phenomenon isn’t explainable with regular color theory, while advanced color appearance models do this and more. As mentioned, standard color theory, found in cameras and software, assumes a fixed, standard viewing condition, while a color appearance model allows for nonstandard viewing conditions.

The CIECAM02 color appearance model is mainly found in computer science grade software. However, it is implemented in Microsoft Windows’ monitor driver, but this isn’t directly accessible by end users. It is also found in the exposure-blending Enfuse software, as well as in RawTherapee. The latter gives you considerable amount of control over it, with the main function of adapting colors for viewing in extremely dark surroundings.

I’ve used both Enfuse and RawTherapee extensively, and CIECAM02 does work, but it is difficult to use well.

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