Cathode sputtering is a well-known technique for deposition of thin films starting from metallic or ceramic materials. Ceramic insulating materials are usually sputtered using radio frequency as electric power source. In this work we compare the optical properties of thin films deposited from two different types of targets. The first set of samples was deposited from solid targets glued to a water-cooled back-plate. For the second set we used targets made of cold pressed (non-sintered) powders of the corresponding materials. The possibility of sputtering from weakly pressed powders can be favourably exploited to develop mixed materials. Their cost, in fact, is about one tenth of glued solid targets, and mixtures of any required composition can be quickly prepared. Two oxides, SiO2 and Al2O3, have been deposited by both methods in the same deposition chamber, using the same process parameters and sputtering gas. Their optical characteristics - refractive index and extinction coefficient - have been compared over the VIS-NIR spectral range.