Absorption measurements performed by means of transverse photothermal deflection technique for wedge-shaped ZrO2, MgF2, ZnS, TiO2, Ta2O5 and SiO2 single-layer films at λ=6328 A permits a separation of bulk and interface absorption. Experimental results show that for ZrO2, MgF2 and ZnS films investigated, the film-substrate interface absorption and the air-film intterfaoe absorption are nearly the same, while for TiO2, Ta2O5 and SiO2 films, the film-substrate interface absorption dominates over the air-film interfaoe absorption, being the main source of tlie total a Sorption loss.