About issues and terminology

Hello again,

since this thread is about terminology, I thought it would be interesting to describe some terms that were used in a series of posts by @Thomas_Mansencal. I hope it will help this group, in order to achieve a new Output Transform.

Please note that I am only here pointing at some documents made by much smarter people than me. :wink: And I am happy to add any source that you may find useful or correct any approximation on my end.

First of all, a book : Colour Appearance Models by M. Fairchild as pointed out by Thomas on Rocket chat. Some proper definitions can also be found in the excellent from Cinematic Color 2. It is also interesting to see that there are approximately four types of color appearance phenomena :

  • Contrast appearance
  • Colorfulness appearance
  • Hue Appearance
  • Brightness appearance

Surround/Viewing Conditions

From Cinematic Color 2 :

The elements of the viewing field modify the color appearance of a test stimulus.

Contrast appearance

Stevens Effect

From Cinematic Color 2 :

The Stevens Effect describes the perceived brightness (or lightness) contrast increase of color stimuli induced by luminance increase.

Simultaneous contrast :

From Cinematic Color 2 :

Simultaneous contrast induces a shift in the color appearance of stimuli when their background color changes.

Colorfulness appearance

Hunt Effect

From Cinematic Color 2 and Wikipedia :

The Hunt Effect describes the perceived colorfulness increase of color stimuli induced by luminance increase. Conversely the colorfulness of colors decreases as the adapting light intensity is reduced. Hunt (1952) also found that at high illumination levels, increasing the test color intensity caused most colors to become bluer.

image

Hue appearance

Abney Effect

From Wikipedia :

The Abney effect describes the perceived hue shift that occurs when white light is added to a monochromatic light source.[1] The addition of white light will cause a desaturation of the monochromatic source, as perceived by the human eye. However, a less intuitive effect of the white light addition that is perceived by the human eye is the change in the apparent hue. This hue shift is physiological rather than physical in nature.

image

Bezold-Brücke Effect

From Wikipedia :

The Bezold–Brücke shift is a change in hue perception as light intensity changes. As intensity increases, spectral colors shift more towards blue (if below 500 nm) or yellow (if above 500 nm). At lower intensities, the red/green axis dominates. This means that the Reds become Yellower with increasing brightness. Light may change in the perceived hue as its brightness changes, despite the fact that it retains a constant spectral composition. It was discovered by Wilhelm von Bezold and M.E. Brücke.

image

Brightness appearance

Helmholtz-Kohlrausch effect

From Wikipedia :

The Helmholtz–Kohlrausch effect (after Hermann von Helmholtz and V. A. Kohlrausch[1]) is a perceptual phenomenon wherein the intense saturation of spectral hue is perceived as part of the color’s luminance. This brightness increase by saturation, which grows stronger as saturation increases, might better be called chromatic luminance, since “white” or achromatic luminance is the standard of comparison. It appears in both self-luminous and surface colors, although it is most pronounced in spectral lights.

Lateral-Brightness Adaptation

From Cinematic Color 2 :

Bartleson and Breneman (1967) have shown that perceived contrast of images changes depending on their surround: Images seen with a dark surround appear to have less contrast than if viewed with a dim, average or bright surround.

image

I haven’t listed all the phenomenons but you will find a more complete list in Cinematic Color 2 Advanced Colorimetry. And if you think it would be useful to list all of them, let me know. I’d be happy to do so.

Hope it helps a bit,
Chris

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