We have reported that a physical reservoir with a silver sulfide island network can classify simple patterns of an irradiated light without converting it to a voltage signal input. In this study, we conducted experiments to verify whether detection of dynamical change in an irradiating light, e.g., moving in a reservoir layer, can be available. We also investigated the potential of the reservoir to detect a position of light exposure and the wavelength dependence, in addition to the existence of exposure time of light to a reservoir. The technique was applied to a task whether characters could be recognized even if the irradiated position was changed.