Nighttime images of a scene from a surveillance camera have lower contrast and higher noise than their corresponding daytime images of the same scene due to low illumination. We propose a denighting method that enhances nighttime images so that they are closer in quality to images taken during the daytime. Our denighting method is based on an observation. It exploits the simple fact that the static camera captures the same scene all day long, obtaining a large quantity of data about the scene. In particular, to enhance the nighttime image, we decompose the image into an illuminance layer, and a reflectance layer that is assumed to be the textures. We enhance the nighttime image by improving the illuminance of nighttime so that it is closer to the illuminance of daytime by using day and nighttime background illuminances that have already been computed. We present several results of the enhancement of low quality nighttime images using denighting.