The problem is outlined of how to approach the description of partially coherent multiple scattering of waves by ensembles of particles in terms of the photometric theory of radiation transport in a scattering medium. The treatment is carried out with the example of a scalar monochromatic wavefield. The apparatus of equations of the Dyson and Bethe--Salpeter types is used. This apparatus is shown to be adequate for the fundamental concepts of transport theory. In particular, correspondence is established between an effective inhomogeneity of an ensemble of correlated particles and the volume element of transport theory. It is shown that neglect of the effect of mutal illumination of correlation groups of particles within a given inhomogeneity leads to spatial localization of the inhomogeneities, while the additional hypothesis that the localized inhomogeneities lie close to one another in the Fraunhofer zone gives the transport equation. The contribution is estimated of the effect of mutual illumination of correlation groups of particles within a given inhomogeneity to the partially coherent scattering of waves by the volume of the medium. The role of the detector of the scattered radiation in making this estimate is discussed.