Visibility

A clear, precise definition of visibility is given. It depends on the modulation transfer function of the light transmitting medium (or contrast loss ratio), the object-to-image distance, the spatial frequency, the medium dispersion (not scattering) coefficient and the medium absorption coefficient. The absorption coefficient, a, and the dispersion coefficient, β, are computed from the experimental modulation transfer function for a region of the ocean. The results obtained confirm the validity of the visibility defining equation.