The light beam is attenuated inside the recording medium. The recording and reconstruction characteristics of the thick hologram grating recorded in such a medium are described, taking into account of the absorption of the recording medium. The profile of the hologram grating is described and the influence of the absorption upon the diffraction efficiency and the angular sensitivity for both the transmission and reflection holograms is calculated using a coupled wave theory. The calculated results are supported with the experimental data obtained with 649F and dichromated gelatin plates.