Abstract

Shape parameters that may control the strength of color induction across contours are examined. The observer views a central shape enclosed by a surround. The surround is modulated sinusoidally in time along a line in color space around midwhite. A joystick is used to null the induced modulation by adjusting the real modulation in the central shape. The amplitude of the nulling modulation is a measure of induction [Krauskopf et al. (1986)]. The central test is modified to independently vary area, boundary length, and parameters that describe its shape. Figures with the same area but varying contour lengths and shapes can be generated by a simple method. The area enclosed by N complete cycles of a sine wave above the mean line is equal to the area below the mean line. If the mean line is bent into a circle, the outline of the sine wave forms a shape with the same area as the circle but a longer boundary. The length and shape of the contour depend on both the amplitude and wavelength of the sine wave (wavelength = circumference of equal area circle/integer).

© 1987 Optical Society of America