  We present an extensive Monte Carlo study on light transport in optically
thin slabs, addressing both axial and transverse propagation. We completely
characterize the so-called ballistic-to-diffusive transition, notably in terms
of the spatial variance of the transmitted/reflected profile. We test the
validity of the prediction cast by diffusion theory, that the spatial variance
should grow independently of absorption and, to a first approximation, of the
sample thickness and refractive index contrast. Based on a large set of
simulated data, we build a freely available look-up table routine allowing
reliable and precise determination of the microscopic transport parameters
starting from robust observables which are independent of absolute intensity
measurements. We also present the Monte Carlo software package that was
developed for the purpose of this study.
