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Johann Friedrich Wilhelm von Bezold was born on June 21, 1837, in München where his father was a minister of state in the Kingdom of Bavaria. He studied natural sciences in München and Göttingen from 1856 to 1860. Already as a child, he was interested in painting, and during his studies at the University of Göttingen, he attended lectures in optics and the physiology of the sensory organs. In 1868, he was named professor of technical physics at the München Polytechnikum. His key research was related to lightning and its dangers as well as thunderstorms, their development and passage through the countryside. In 1885, he was offered a professorship in meteorology in Berlin. In this position, he organized the establishment of the system of weather information in Germany. He is considered the initiator of the field of thermodynamics of the earth’s atmosphere. He was elected a member of the Prussian Academy of Sciences. Bezold passed on February 17, 1917, in Berlin [1].
44.1 Bezold–Brücke Effect
Between 1873 and 1876, he published half a dozen articles on binocular vision, color mixture and presumed physiologically basic colors. It should be mentioned that during his adult time in München, he also was an art critic writing for several newspapers. In 1876, his book Die Farbenlehre im Hinblick auf Kunst und Kunstgewerbe (The theory of color in its relation to art and art-industry) was published, in the same year also in an English edition in the USA and one year later in a Russian edition. A revised second German edition was published in 1912. The book established von Bezold’s broad reputation in the field of color and its connection to art.
In his scientific article “Ueber das Gesetz der Farbenmischung und die physiologischen Grundfarben” (On the law of color mixture and the physiologically fundamental colors), published in 1873, he reported experimental findings showing changes in apparent hue due to changes in luminance or lightness of the stimulus [2]. This was later also found to apply to the Munsell system where the location of the stimuli in the CIE chromaticity diagram usually differs as a function of lightness to a smaller or larger extent from one Munsell value level to the next, with only a few exceptions of hues. Over the years, the effect has been investigated multiple times by different methods with results differing somewhat by method as well as by observer. There are three wavelengths where the appearance generally does not change depending on luminance or lightness, ca. 470, 510, and 575 nm. The deviations are largest near the long-wave end of the spectrum. The three constant wavelengths coincide approximately with the average wavelengths of stimuli considered to represent unique hues. The effect had briefly been mentioned already in 1866 by the physiologist Ernst Wilhelm von Brücke (1796–1873). As a result, the effect became known as Bezold–Brücke Effect.
Examples of the Bezold color assimilation effect. The reddish colored squares on the left side and the greenish colored ones on the right have on top and bottom identical stimuli [4]