A photoreceptor including an electroconductive substrate, a photosensitive layer located overlying the substrate, and a protective layer overlying the photosensitive layer, wherein the photoreceptor has a property such that when the photoreceptor is charged so as to have a potential of -700 V and then exposed to light with exposure of 0.4 .mu.J/cm.sup.2, the potential (P.sub.L) of a lighted portion of the photoreceptor decreases at a rate not greater than 700 V/sec during a time period of from a time 35 msec after the exposure to the transition time of the photoreceptor. An image forming apparatus and a process cartridge including the photoreceptor are also provided.