In order to study the electronic and optical properties of complex materials an approach providing a reliable estimate of band gaps in combination with the reasonable description of the ground state is required. In the present study of pure and defective perovskite crystals, the fulfillment of such requirements is clearly demonstrated using a simple hybrid HF/DFT scheme containing an admixture of non-local Fock exchange. In present theoretical investigations, a wide class of perovskite oxides is represented by three, the most attractive (from a scientific point of view) crystals of SrTiO3, BaTiO3, and PbTiO3 in their high symmetry cubic phases. These perovskite crystals present a great technological and fundamental interest due to their numerous applications related to ferroelectricity, non-linear and electro-optics, superconductivity, and catalysis. Although the above-mentioned perovskite-type materials have been intensively investigated theoretically and experimentally at least in the last fifteen years, a proper description of their electronic properties is still an area of active research. In order to make a contribution to the explanation of various electro-optical effects observed in perovskite materials, their ground-state properties have been calculated from first principles and analyzed in the present study.