© Springer Nature Switzerland AG 2020
R. Shamey, R. G. KuehniPioneers of Color Sciencehttps://doi.org/10.1007/978-3-319-30811-1_51

51. König, Arthur Peter 1856–1901

Renzo Shamey1   and Rolf G. Kuehni1  
(1)
Color Science and Imaging Laboratory, North Carolina State University, Wilson College of Textiles, Raleigh, NC, USA
 
 
Renzo Shamey (Corresponding author)
Email: rshamey@ncsu.edu
 
Rolf G. Kuehni
Email: rolf_kuehni@ncsu.edu
51.1 Cone Spectral Sensitivity Functions
References
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Arthur Peter König was born in Krefeld, Germany on September 13, 1856. His father was a teacher; his mother died when he was 2 years old, and he was mainly raised by an aunt. König suffered from birth from congenital kyphosis and was physically handicapped. However, he was an excellent pupil. After graduating from gymnasium, he began a merchant’s apprenticeship. Nonetheless, soon he was able to study at the Bonn and Heidelberg Universities and in 1879 at Berlin University where he formed a relationship with one of his professors, Hermann von Helmholtz. He obtained his Ph.D. degree in physics in 1882 and became an assistant to Helmholtz. He was named an associate professor in 1884 and in 1889 a full professor at the physical division of the physiological institute. His special duty was to lecture on physiological optics. Together with Hermann Ebbinghaus, he founded the Zeitschrift für Psychologie und Physiologie der Sinnesorgane (Journal for Psychology and Physiology of Sensory Organs) and was editor of two additional scientific journals. Together with Helmholtz, he edited the second edition of the latter’s Handbuch der physiologischen Optik (Treatise on physiological optics), published after Helmholtz’s death (in 1894) in 1896. Among other reasons, it is famous for containing a list of 7833 published articles on the general subject, accumulated by König. Several well-known psychophysicists passed through König’s laboratory, among them Christine Ladd-Franklin. At the beginning of the twentieth century, König’s health deteriorated and he died on October 26, 1901, at age 45. The successor in his position was Willibald Nagel [1].

51.1 Cone Spectral Sensitivity Functions

König published a number of papers on subjects related to physics but his most important contributions are those on physiological optics, a number of them co-authored by a student of Helmholtz, C. Dieterici. The articles have been conveniently collected by König and were jointly published in 1903 [2]. For some 50 years Helmholtz and Ewald Hering had been in a battle about color vision with the former quantitatively formulating and expanding on Young’s three-sensor types theory and Hering, based on visual experience, proposing an opponent-color theory. Much of the work of König was to offer support for Helmholtz’s theory.

Perhaps the most important of König’s papers (together with C. Dieterici) were two describing the findings of their experiments determining the spectral sensitivity functions of the three implied cone types (Fig. 51.1) [3, 4]. They found that color-normal individuals varied noticeably in their results and that dichromats only had two such functions. In the figure, the functions V (violet) and R (red) are close enough for König and Dieterici to have single curves. This is different for the G (green) curve where K and D indicate the functions for each investigator. König interpreted the differences in the curves between 550 and 430 nm to be due to individual differences in macular pigmentation. The dashed curve is representative of the spectral sensitivity of the rod sensors. In their second paper, based on additional experimental data, König and Dieterici concluded that the three fundamental functions are sufficient to describe the basics of color vision and that in case of dichromatic observers either cones of the R or the G type were missing. For anomalous trichromats, they found that two fundamentals were identical with those of a color-normal observer while the third one is significantly different [4]. The data became known as the König fundamentals and were used for colorimetric calculations until, from experimental results by J. Guild and W. D. Wright, the CIE standard observer data were calculated in 1931.
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Fig. 51.1

Experimentally determined spectral sensitivity functions of the three cone types, identified as V, G, and R and that of the rods shown as a dashed line. The letters below the wavelength scale represent the locations of major Fraunhofer lines [2]

Other important investigations involve the determination of wavelength discrimination ability [5], experimental determination that Grassmann’s laws of color mixture depend on light intensity [6], the dependence of Fechner’s law on light intensity and to a degree on wavelength of comparison [7] and the perceived brightness of spectral hues at different light intensities [8]. An area of interest in the 1890s was the earlier identified visual purple discovered in 1877, then assumed to be the basis of color vision. Experiments by König showed that the light absorption of visual purple is in close agreement with the single sensitivity function of monochromats but different from the three functions of the normal trichromat [9].