Based on the light extinction of total internal reflection by triangular prisms, very sensitive detection of the shock front and fast moving free surface has been demonstrated for 1 GPa shock waves in polymers. This is the first experimental verification of the feasibility of the inclined-prism technique for the relatively low shock stress region, which was originally proposed and used by Eden and Wright for obtaining the high-explosive generated shock Hugoniot of several condensed materials. The present method has the advantage that it only requires closing the gap between the free surface of the target and the reflected surface of the prisms. The feasibility and the limitation of the method have been discussed both theoretically and experimentally. A typical streak photograph for a PMMA specimen is shown to compare with the published data. It is seen that the present method is very sensitive for shock arrival detection even in the 1 GPa shock stress region. ©1998 American Institute of Physics.