Indium selenide, InSe, is known as a semiconductor with unusual properties. Studying the effects of doping with dysprosium on the electronic and physico-chemical properties on InSe single crystals, the authors observed another rare phenomenon, which is described here. The authors found that, at certain dysprosium contents N{sub Dy} and temperatures, the residual photoconductivity of InSe{l_angle}Dy{r_angle} crystals is independent of light intensity {Phi} and depends only on wavelength {lambda} over a wide range of {Phi}. This phenomenon is interesting from both practical and scientific points of view. The results can be useful in designing sensors and color memory cells and in studying mechanisms of electronic processes in both partially disordered semiconductors in general and layered III-VI crystals in particular.