Report No. 5-1. Contract NObs-72039. The observable reflectance function, sometimes called the "up-down ratio," for natural light in the sea is nearly independent of depth within any uniform water-mass or stratum. Even small changes, however, may affect the range at which a downward looking observer can sight an object of very low contrast. This report presents a theoretical s tudy of the variation with depth of the observable reflectance function for natural light in the sea.
