Contents

16 June 1972
Vol 176, Issue 4040

About The Cover

Multicolored chalk drawing by Jeanne L. Benton. Top photograph was taken in uniform 656-nanometer illumina-tion; the bottom in uniform 546-nanometer illumination. This drawing was used with controlled nonuniform 656- and 546-nanometer illumination to produce two different color sensations from physically identical stim-uli. The radiance for each wavelength was also controlled so that only the rods and long-wave cones were above threshold. See page 1255. [Julius J. Scarpetti, Vision Reseach Labora-tory, Polaroid Corp., Cambride, Massachusetts]