Figure 4.

Speed ratings of red-green gratings as a function of green/red saturation ratio |G|/|R| and the contrast of an added luminance grating. The dotted lines indicate the points at which the added luminance grating produced isoluminance in the calibration procedure. The moving grating was 0.5 cycles/deg, 2 Hz, speed 4 deg/sec, 8% contrast in DLK space, and was viewed at eccentricities of 3.5 and 4.5 deg (observers LL and HK). The rated speed of a matched, 8% contrast black-white grating is taken as 100%. The numbers in the graph indicate the speed of the black-white grating to which the speed of the color grating was matched. Each point is the average of three judgments made in consecutive sessions. 0 indicates absolute standstill on all trials.