An image forming apparatus includes temperature sensors that measure temperatures at different locations in the longitudinal direction of a photosensitive drum. The image forming apparatus also includes an image processing circuit configured to change an exposure condition in the longitudinal direction of the photosensitive drum based on measured values obtained by the temperature sensors. A related image forming method includes calculating a temperature at a third location between the first and second location based on the measured temperatures at the first location and the second location, and controlling an exposure condition for exposure at the third location in accordance with image information, including changing the exposure condition for the exposure at the third location based on the calculated temperature at the third location.