  New approach on interpretation and processing of Raman spectra of complex
perovskites is suggested. Raman spectra of $PbMg_{1/3}Nb_{2/3}O_{3}$ and $%
PbSc_{1/2}Ta_{1/2}O_{3}$ are successfully described on the basis of the
phonon-confinement model and validity of the method is demonstrated on good
agreement of experimentally obtained and computer simulated spectra of another
complex perovskite, $BaMg_{1/3}Ta_{2/3}O_{3}$. The study showed that the size
of nanoscale regions is a kind of an inborn characteristic of the sample and is
not temperature dependent. For $PbSc_{1/2}Ta_{1/2}O_{3}$, two special
temperature points, approximately 400 K and 600 K are found from the analysis
of the temperature behaviour of obtained mode parameters.
