An image formation apparatus such as a copying machine has a standard white plate, an optical system for forming a latent image on a photosensitive drum, a photosensor such as a linear image sensor for detecting the amounts of light reflected from the standard white plate and an original, and a control section including a CPU and an exposure control circuit and/or a bias control circuit for controlling the light exposure amount or the developing bias voltage in accordance with the difference between the light amounts from the standard white plate and the original.