The functions, w = ƒ(z), that describe the transformation of Fresnel’s reflection coefficients of parallel and perpendicularly polarized light between normal and oblique incidence, as well as their inverses, z = g(w), are studied in detail as conformal mappings between the complex z and w planes for angles of incidence of 15, 30, 45, 60, and 75°. New nomograms are obtained for the determination of optical properties of absorbing isotropic and anisotropic media from measurements of reflectances of s- or p-polarized light at normal and oblique incidence