1. An image forming apparatus comprising: an image carrier; an exposing unit configured to form an electrostatic latent image including dot images based on image data, by exposing a surface of the image carrier with exposure energy in accordance with pixels in the image data, wherein each of the dot images corresponds to one of the pixels; and a developing unit configured to perform a developer contact developing method by applying a developing bias onto a developer carrier carrying a non-magnetic one-component developer and causing the non-magnetic one-component developer on the developer carrier to contact the image carrier, thereby developing the electrostatic latent image on the image carrier into a toner image, wherein: the toner image on the image carrier is transferred onto a recording material, either directly or via a surface of an intermediate transfer body; and the developing bias or the exposure energy is adjusted such that an isolated one-dot image has a predetermined image density, the image forming apparatus further comprising: a control unit configured to control the exposing unit in such a manner that, when the image carrier is exposed to form the dot images which are continuously arranged in a sub scanning direction, an exposure time period for each of the dot images is shorter than a time period for exposing the image carrier to form the isolated one-dot image.