Instruction on Light and Color in Art at the Iowa State University

Leormrdu, Vol. 9, pp. 52-55. Perganion Press 1976. Printed in Great Britain INSTRUCTION ON LIGHT AND COLOR IN ART AT THE IOWA STATE UNIVERSITY Mary L. Meixner* 1. In the Applied Art Department at lowa State University Ames, lowa, U.S.A., we affirm the significance of light and its applications in art, architecture and interior design. As part of the program in our color classes, we attempt to clarify the processes of subtractive and additive color mixing and to study the effects of illumination of objects on the colors perceived. A useful demonstration for subtractive color mixing is the Balinkin-Dwight Filtergraph (Fig. 1) made by the Sargent-Welch Scientific Co., Skokie, Ill., U S A . It consists of a cabinet having interior walls painted white, an achromatic light source and a window that can accommodate single or superimposed pairs of plastic plates. Each plate shows a graph above and a single color filter below. The graph gives a wavelength composition of each color, its spectrophotometric curve. For an art student this is the critical step toward understanding that merely to name a color as it is perceived does not fully identify a filter. Figure I shows two superimposed plates. The single curve that starts at a wavelength of about 460 m p and rises to a plateau corresponds to yellow-green. The entire area under that curve represents transmitted light when only that plate is present and the entire area above that curve represents absorbed light. The individual filters are first studied singly. For example, orange and amber can be perceived as being very close, however the curve for the amber filter shows that a relatively large amount of radiation in the red and violet is transmitted When two plates, representing different colors, are superimposed, as in Figure I, the resulting mixed color appears in the central diamond shape with areas left for the two mixture parents at its sides. The resultant light transmission is represented by the area in which the two spectrophotometric curves overlap (e.g. the white area peaked at about 490 m p in Figure I). The mixed color perceived in the central area is of lower intensity than that of either of the unmixed colors perceived(to the right and left). This isexpected because radiant energy is lost on passage through each filter. The Singerman Apparatus (Fig. 2), also made by the Sargent-Welch Scientific Co., is used to demonstrate additive color mixing. It consists of a cubical cabinet having interior walls painted mat black and a ground glass projection screen on one side. There are three clear incandescent lamps installed inside, whose emissions can be controlled independently from ‘dim’ 111. to ‘bright’ by means of rheostats. Each lamp is housed behind a circular opening to provide a conical beam. Three overlapping circular areas are illuminated as shown in Fig. 2. Seven different filters in metal holders are provided for inserting into the box to intersect the three light beams individually. In Fig. 2 three filters are used conforming to the perception of red, green and blue (the additive primaries). When superimposed with proper adjustment of the rheostats they produce achromatic ‘white’ at the center. It is logical here that, since the radiant energies of the three sources are added, the intensity of the resulting illumination is increased. Thus the color at the center in Fig. 2 has the greatest luminosity. The increase in luminosity can be convincingly demonstrated by superimposing the light from the three light sources minus the filters. After-images can be produced using this device. If the red circle alone is viewed steadily for several minutes and then withdrawn, the remaining white circle will appear cyan. The overlapping of light rays on a surface to produce additive mixing in the Singerman Apparatus is reproduced directly in many kinds of art objects utilizing n * Artist and teacher, Applied Art Department, Iowa State University, Ames, I A 50010, U.S.A. (Received 7 July, 1974.) Fig. I . Bo/itrkitr-Di~~i6~/11 Filiwgrcrpli. (Photo: SargentWelch Scientific Co.) 52 Instruction on Light and Color in,Art at The Iowa State University 53 Fig. 2. Sirigeririori Apparatrrs. (Photo: Sargent-Welch Scientific Co...