Considerations are given for light sources adopted usually in photography, namely, the strobotron, the flush light, and the incandescent lamp. The former two cause harmful effects of deterioration for the object, and the latter is apt to cause mechanical damages by generation of heat. For each flush of the former two light sources, an estimation is made on equivalent harmful time of incandescent lamp illumination, that is of 3200°K color-temperature and at 300 lux in illuminance. Limitation of lux value to be imposed on the incandescent lamp illumination in regard to heating effect is argued, and a proposal is made that temperature rise at the surface of the illuminated object must be within 1. 5°C, or illuminance within 700 lux when we illuminate weak Japanese art objects. Infra-red absorbing filters are recommended for adaptation to incandescent lamps, if high illuminance is required. -- AATA