An image forming apparatus includes a lubricant application device to apply a lubricant to a photoreceptor surface of the image forming apparatus, and a lubricant residual amount detector to detect a residual amount of the lubricant. The residual amount of the lubricant is compared to a predetermined amount, and a charging device charges the photoreceptor surface by selectively applying a DC voltage of varying voltage to the photoreceptor surface in response to the comparison of the residual amount of the lubricant to the predetermined amount.