The problem is discussed of the statistical and wave content of photometric concepts. The photometric and statistical definitions of the concept of radiance of illumination are treated. We stress that photometry describes the limiting case of a statistically quasihomogeneous and quasistationary wave field. The relationship of the phenomenological and statistical approaches to the theory of radiation transport is traced with the example of the problem of diffraction of the radiation from plane sources. The concept is discussed of the generalized radiance, which enables one partially to take into account within the framework of the radiation transport theory diffraction effects by a transition from the phenomenological radiance to the local spectrum of a quasihomogeneous field. We present also the fundamental results on the statistical and wave substantiation of the theory of transport in scattering media.