Karl Ewald Konstantin Hering was born on August 5, 1834, in Alt-Gersdorf in Saxony, son of a Lutheran pastor and his wife. He studied medicine at the University of Leipzig, obtaining an MD degree in 1860. For the next five years, he practiced medicine in Leipzig and pursued personal interests in vision on the side, publishing five Beiträge zur Physiologie (Contributions to physiology) between 1861 and 1864 [1]. He was married in 1863, and he and his wife had a son, Heinrich Ewald. In 1865, he was appointed professor of physiology at the Josephinum Academy in Vienna. In 1870, he became the successor of J. E. Purkinje as professor of physiology at the University of Prague where he remained for 25 years, studying among other things the electrical actions of nerves and muscles, as well as the perception of light and color vision. In 1895, he was invited to join the University of Leipzig where he remained until his retirement in 1915. During his lifetime, Hering assumed the role of anti-Helmholtz, scientifically and philosophically battling with him concerning several subject matters [2]. Hering died on January 26, 1918, in Leipzig.
43.1 Opponent-Color Vision Theory
Hering developed a theory, alternative in detail to that of Helmholtz, concerning spatial perception based on images in two eyes. Publication of and the response to Helmholtz’s first edition of the Handbuch der physiologischen Optik in 1867 [3] provided a basis for Hering to consider in detail the issues of color perception and develop his own, different theory. The result was the presentation in 1874 of six extended contributions to the Imperial Academy in Vienna, published in book format in 1878 as Zur Lehre vom Lichtsinne (On the theory of the light sense) [4]. Hering considered the Young–Helmholtz theory to give too much weight to physics and not enough to the perceptual aspects of color. In response, he developed an opponent-color theory postulating three opponent pairs of fundamental colors (Urfarben), yellow–blue, red–green, and white–black, building on earlier ideas by H. Aubert and E. Mach. The hues are arranged according to simple principles in a hue circle (Fig. 43.1), the complete arrangement of all colors of a given hue being in a triangle, with white, black, and full color at the corners and “veiled” colors filling the interior. Hering called the result, in the form of a double cone, the “natural color system.” He also proposed dissimilation/assimilation processes in the eye/brain as physiological basis of the opponent system, in opposition to the Young–Helmholtz theory involving three fundamentals. A commercial version of the Natural Color System atlas was introduced in 1979 by the Scandinavian Color Institute as the Swedish Natural Color System (NCS).
Fig. 43.1
Superimposed images of the conceptual mixture of the four hue fundamentals in different ratios and the resulting hue circle; derived from two images in Hering, 1878 [4]
Today, the perceptual aspects of Hering’s system continue to be considered essentially valid, with its physiological part being short of reality. Despite many attempts a psychophysical model of the four hues, presumed fundamental and their mixtures, that also meets other components of the colorimetric system is still lacking at this time. A major issue is the fact that while mean unique yellow and blue stimuli are essentially complementary, unique green and unique red stimuli are far from it, complicating any model with the purpose of representing a perceptually meaningful and at the same time colorimetrically valid model.
