[en] Recently, a new class of phosphors (Eu²⁺ doped alkali-earth halides) have been introduced which are able to store X-ray information for hours and allow a recovery of this information by optical stimulation within microseconds. This SPP (Storage Photostimulable Phosphor) technology has been investigated for application to medical X-ray imaging and is well proven in molecular biology and radioluminography research. Depending on the application, different requirement exist for the sensitivity and spatial resolution of the film, and these are related to light scattering in the film. The purpose of this study is to investigate the characteristics of the thin SPP plates light propagation mechanism. The influence of the scattering length, absorbance is calculated based on the light diffusion model. The sensitivity, resolution and other image properties are determined from the optical properties. The results indicate that optimizing the image properties of the film can be achieved by a reduction of the absorbance and an increase in film thickness to the penetration depth of the X-rays.