Terminology

Leonardo, Vol. 9, p. 147. Pergamon Press 1976. Printed in Great Britain TERMINOLOGY The terms defined below were selected from artists’ Articles and Notes published in the previous issue of Leonardo. Each definition is followed by an indication of the volume and page number of Leonardo on which the term first appears. The terms were not found in the art dictionaries among the dictionaries listed in Leonardo 9, 67 (1976) or they are used in a new sense. Some are terms that have been carried over into the field of art from the natural and social sciences, from mathematics and from technology. Numbers in brackets, e.g. [ll, 171,refer to the dictionaries mentioned above. The definitions are not presumed to be unassailable. The Editors would, therefore, welcome the comments of readers on the definitions presented. 733. Colorrenderingindex(in illmiination eiigineeritig)A measure, on the scale0 to 100,that is intended to indicate the degree to which the color rendering properties of an electric lamp illuminating certain color standards approach those of a standard electric lamp. The index is derived from a determination of the mean color change in a series of Munsell color chips when the lamp being tested is replaced by the standard lamp. (9, 53; [M. B. Halstead, J. F. Bull and F. E. Lange, A Proposed Dual Index for Expressing the Colour-Rendering Properties of Lamps, in Coloitr 73 (London: Adam Hilger, 1973) p. 3571) (cf. Mitnsell color chip, term 738) 734. Color solid (iiJ color science)-A 3-dimensional figure that can be used to represent discriminable color differences by distances in a 3-dimensional coordinate system (color space) (not necessarily Euclidean space) in which dimensions correspond to the three color dimensions (hue, saturation and lightness) or to the three variables required to specify a color in a color system. (9,48; [R. W. Burnham, R. M. Hanes and C. J. Bartleson, Color: A Guide to Basic Facts and Concepts (New York: John Wiley, 1963) p. 1611) (cf. Mitnsell color chip, term 738) 735. Color space (in color science)-(cf. Color solid, term 734) 736. Gelatin filter (in physics)-A filter of light made of dyed gelatin. Gelatin filters are used in front of light sources, such as stage lights, to alter the spectral characteristics of the light output. (9, 53; 1111) 737. Millimicron (in physics)-(cf. Nanometer, term 739) . 738. Munsell color chip (in color science)-A standard color sample in the form of a removable swatch from a collection (glossy and mat finishes) contained in The Miinsell Book of Color, 2 vols. (Baltimore: Munsell Color Co., 1947). The samples are classified according to the Munsell system in which Munsell hue, value and chroma correspond roughly to the attributes hue, lightness and saturation in color perception. (9, 53; [R. W. Burnham, R. M. Hanes and C. J. Bartleson, Color: A Guide to Basic Facts and Concepts (New York: John Wiley, 1963)]) (cf. Swatch, term 745) 739. Nanometer (nm), millimicron (mp) (inphysics)-A unit of length equal to one millionth of a millimeter. The wavelength of light is commonly measured in nanometers (millimicrons). (9, 52; [3]) 740. Nonspectral colors (in color science)-Colors characterized by hues ranging continuously from red, through magenta and purple to violet. The sensation of a nonspectral hue cannot be produced by light of a single wavelength, as can spectral hues. (9,48; [R. W. Burnham, R. M. Hanes and C. J. Bartleson, Color: A Guide to Basic Facts and Concepts (New York: John Wiley, 1963) p. 1351) (cf. Spectral colors, term 743) Rheostat (in electricity)-A device placed in an electric circuit whose resistance can be varied in order to control the electric current in the circuit. (9, 52) 741. 742. Rhombohedron (in nmtheniatics)-A solid formed by six plane faces each having four straight sides of equal length and the opposite angles equal (two being acute and two obtuse). (9, 48; 1161) 743. Spectral colors (in color science)-Colors characterized by hues ranging continuously from violet through indigo, blue, green, yellow, orange and red. (9, 48; [ll]) (cf. Spectritm, Terminology, Leonardo 7, 166 (1974)) 744. Spectrophotometric curve (in color science)-A plot of the rate of flow of radiant...