ts.
Indeed, thoughtful artists rejected this color theory nonsense almost from the beginning. Here for example is John Ruskin, writing in 1862 about the depth effect:
It is a favourite dogma among modern writers on colour that 'warm colors' (reds and yellows) 'approach,' or express nearness, and 'cold colours' (blue and grey) 'retire' or express distance. So far is this from being the case, that no expression of distance in the world is so great as that of the gold and orange in twilight sky. Colours, as such, are ABSOLUTELY inexpressive respecting distance. It is their quality (as depth, delicacy, etc.) which expresses distance, not their tint [hue].
An Optical Illusion. Undeterred by Ruskin's critique, Joy Turner Luke offers an explanation for the depth effect that has become popular recently: warm colors are "advancing" because their focal length is longer than cool hues, which is the cause of chromatic aberration.
All hues cannot be perfectly focused at the same time. The eye focuses slightly differently on long wavelengths (reds) than on short wavelengths (blues). The lens becomes slightly fatter and more curved to focus on red in comparison to when it is focusing on a blue or green. ... When the eye focuses on nearby objects it makes a similar, but larger, change than it does when focusing on red; ... the muscles that control the lens are most relaxed when we gaze off into space. This small difference in focus may account for the fact that blue and green seem more relaxing and to recede slightly in space.
This explanation doesn't work for three reasons. First and most important, our eyes are adapted in many ways to eliminate chromatic aberration from visual experience. Depth perception is critical to primate survival, and objects that "advance" or blur because of their surface color would destroy that acuity. We simply never see aberration effects, unless they are produced by cheap artificial optics. The focusing of our eyes, the appearance of objects and our color associations cannot be influenced by optical effects we never see!
Second, optical accommodation (the focusing of the lens) is an extremely weak depth cue (note Luke's use of "slightly" and "small"). In studies that have looked at various depth cues, optical accommodation to object distance (even though it is a "larger change" in the lens) has an inconsequential effect on depth judgments for objects more than a few feet away.
Finally, in everyday experience we see red and blue objects together, as part of a unified, three dimensional world. Luke's "relaxation sensation to invisible aberration" could only be experienced by focusing on monochromatic lights viewed in isolation first a pure "red" pattern and then a pure "blue" one. And in that context humans are nearsighted to blue light.
chromatic aberration and focal length
humans are nearsighted to "blue" light, which means an object comes into focus as it moves closer to the eye
The difference in the angle of refraction between "red" and "blue" light is equivalent to an extremely large difference in the distance of two objects, assuming no accommodation occurs in the eye (diagram, above). That is, if you cover one eye and focus on a line grating of monochromatic "red" light 100 yards away, a line grating of monochromatic "blue" light just two feet away would be in focus at the same time. Wherever we looked, our experience of the world would be of near, in focus blue objects or refractions popping out of a field of view anchored on distant, in focus warm objects.
This separation is visible in rare situations, such as an ultraviolet light viewed in darkness: the physical source, which appears in shades of pink or red, is surrounded by an unfocused, but apparently closer, violet nimbus. But this peculiar effect is clearly unusual, so it too cannot provide the hypothetical associations claimed to produce warm/cool contrast effects.
Lightness and Chroma. OK, so what does explain the qualitative differences between warm and cool colors? As with any complementary color contrast, lightness and saturation strongl