© Springer Nature Switzerland AG 2020
R. Shamey, R. G. KuehniPioneers of Color Sciencehttps://doi.org/10.1007/978-3-319-30811-1_78

78. Evans, Ralph Merrill 1908–1974

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
78.1 The G0 Function
References
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ISCC.org

Ralph Merrill Evans was born in 1908 in Massachusetts. After schooling at the Phillips Academy in Andover, MA, he attended Massachusetts Institute of Technology from which he graduated in 1928 with a B.S. degree in optics and photography. He worked briefly for Kodak Corporation, moving on to Twentieth Century Fox Film Corporation in New York in 1929 where he worked in research and quality control until 1933. He returned to Kodak where he became supervisor in the color process development department. In 1945, he was named superintendent of the color control department and in 1953 director of the Color Technology Division. Some years later, a reorganization at Kodak resulted in Evans being placed in charge of the Photographic Technology Division, a position he occupied until his retirement in 1970. Evans died on Jan 29, 1974 [1].

Evans was convinced that better understanding of color perception would result in improved color photography and printing, and he proposed the hiring by Kodak of young researchers with new ideas about color to do color perception research. Among these were Dorothea Jameson and Leo Hurvich who did research work at Kodak from 1947 to 1957.

Evans published some fifty scientific and technical articles on color and photography, and he is the inventor or coinventor in 17 patents. He was an active member of several color- and photography-related societies, including the Inter-Society Color Council where he was given the Godlove Award in 1959 [2]. He was well-known for his presentations at conferences that always included cleverly prepared slides to illustrate key points. Evans also authored and co-authored four books related to the subject of color. His 1948 book An introduction to color was considered a path-breaking text on color perception at the time, describing many color perception phenomena and illustrating them with color plates. It covers also some issues related to color photography and the effect of different light sources on the outcome in the photographic image. Two of his books specifically covered the subject of color photography: Principles of color photography (1953) and Eye, film and camera in color photography (1959). His final book The perception of color was published posthumously in 1974 with the help of his colleague and co-researcher Bonnie K. Swenholt. It is an updated and more specialized text on color perception that addresses the effect of surrounds of different kinds on the appearance of an object in detail [3].

78.1 The G0 Function

In his later years, Evans became more and more interested in the appearance of color stimuli under specific conditions, such as unrelated and related, and in the latter case the relationship between the luminance of the surround stimulus and that of the central test stimulus. Based on experiments, he concluded that against a white surround of a certain luminance, colored test stimuli have a grayish appearance that diminishes steadily as its luminance increases up to a point where the apparent grayness disappears. With further increasing luminance of the test stimulus begins to have a fluorescent (or fluorent) appearance against the surround that increases as the luminance increases. Evans found the zero-grayness point to vary across the spectrum as a function of dominant wavelength (Fig. 78.1).
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Fig. 78.1

Evans’ G0 function across the spectrum in terms of dominant wavelength, achromatic surround at 100 mL, observer RME [3]

He gave fluorence the name “brilliance” and the perceptual parameter ranged from full grayness to zero-grayness. He concluded that chromatic stimuli have five independent variables: hue, saturation, lightness, brilliance, and brightness. Evans’ G0 concept has become a component of various color appearance models. It represents the finding of an aspect indicating how complex color appearance is and that attempting to constrain it to three dimensions is not realistic.