This is a follow up article to the first article  in which we developed the mathematical tools to determine the optical properties of optical thin film materials from the measured spectral data for a single layer coating. In the previous article we also demonstrated that there was a very good correlation between the calculated optical properties and the design properties where the films were homogeneous and the precision of the data was very good, out to five decimal places. In the real world we do not make homogeneous films (i.e. they all have at least a little bit of inhomogeneity) and our spectral measurements are not accurate to five decimal places. In this article we will discuss the effects of inhomogeneity on the spectral performance of optical thin films, we will discuss techniques of making routine spectral measurements for characterization and we will demonstrate the results characterizing actual deposited thin film materials.