An image forming apparatus comprising: photo conductor means; charging means configured to charge a surface of the photo conductor means; exposure means configured to expose the charged surface of the photo conductor means and to form an electrostatic image thereon; developing means configured to attach toner to the electrostatic image and to develop the electrostatic image as a toner image; and control means configured to control an exposure condition for exposure performed by the exposure means in accordance with image information, the control means being operable to change the exposure condition for exposure performed by the exposure means in a longitudinal direction of the photo conductor means; characterised by: temperature measuring means configured to measure temperatures in at least two different locations in the longitudinal direction of the photo conductor means; and further characterised in that the control means are operable to determine a temperature distribution of the photo conductor means in the longitudinal direction thereof based on the temperatures measured in said different locations by the temperature measuring means, and are further operable to change said exposure condition in the longitudinal direction of the photo conductor means based on the determined temperature distribution. photo conductor means; charging means configured to charge a surface of the photo conductor means; exposure means configured to expose the charged surface of the photo conductor means and to form an electrostatic image thereon; developing means configured to attach toner to the electrostatic image and to develop the electrostatic image as a toner image; and control means configured to control an exposure condition for exposure performed by the exposure means in accordance with image information, the control means being operable to change the exposure condition for exposure performed by the exposure means in a longitudinal direction of the photo conductor means; characterised by: temperature measuring means configured to measure temperatures in at least two different locations in the longitudinal direction of the photo conductor means; and further characterised in that the control means are operable to determine a temperature distribution of the photo conductor means in the longitudinal direction thereof based on the temperatures measured in said different locations by the temperature measuring means, and are further operable to change said exposure condition in the longitudinal direction of the photo conductor means based on the determined temperature distribution. temperature measuring means configured to measure temperatures in at least two different locations in the longitudinal direction of the photo conductor means; and further characterised in that the control means are operable to determine a temperature distribution of the photo conductor means in the longitudinal direction thereof based on the temperatures measured in said different locations by the temperature measuring means, and are further operable to change said exposure condition in the longitudinal direction of the photo conductor means based on the determined temperature distribution.