A Fourier transform (FT) approach based on the evaluation of optical-density-bandwidth products in the spectral region of interest was recently proposed for the thickness estimation of reflecting thin-film dielectric filters. For simplicity, the initial discussion was limited to a particular type of immersed coating. The theory is generalized to more realistic filter configurations and confirmed by numerical examples. It is shown that good results are possible although the problem is more complex from a FT point of view.