Optical techniques that use a spectral range of photon energies larger than the band gap are very sensitive for structural characterization of semiconductor nanocrystals. Techniques that can measure the change of polarization during reflection from bulk or thin film samples reveal high sensitivity for both the layer thickness and the refractive index. From one spectroscopic ellipsometric measurement performed in a range of 0.7-6.5 eV within 1 s using a standard multi-channel ellipsometer not only the thickness and the dielectric function of the film, but a range of derived material properties like the crystallinity or the size and volume fraction of nanocrystals can be determined indirectly. The quality of the measurement is not any more a question of instrumentation, but rather a question of interpretation and proper modeling. In this paper we summarize what parameters can be determined, and we present a method for the reliable fitting of numerous parameters.