Detection of oil films and their discrimination from, e.g., biogenic films is a very important ecological problem. Remote sensing methods, particularly, satellite methods are the most perspective for the problem solution. Films in the sea surface optical images can be seen because of changing a) the reflected radiance due to strong depression of short gravity-capillary waves by films and b) the reflection coefficient when considering light reflection from the upper and lower film boundaries. But the effects are strongly determined by film parameters. Natural biogenic films spread down to monomolecular layers and can be characterized by the elasticity and the surface tension coefficient. Oil films have finite thickness and wave damping due to these films is determined by larger number of physical parameters, than biogenic films, namely by the oil density, film thickness, viscosity and elasticity of two film boundaries, etc. Possibilities of filmslick detection and characterization using optical systems of low spatial resolution are analyzed. The threshold values of the film parameters at which film slicks can be detected with these systems are estimated at different observation/illumination conditions and wind regimes. The principal possibility to estimate the film parameters and to identify oil films is demonstrated using a theoretical model. Experimental verification of the model is presented based on measurements of the sea surface radiance contrast in slicks with known film parameters.