In this hunt using a direct light sensor, the brightest areas will likely be where light sources or reflective surfaces are directly in the sensor's line of sight.
Windows or light fixtures could create bright spots. Conversely, the sensor may detect less light in areas shadowed from direct illumination, such as corners or behind obstructing objects. It won't capture light that is scattered or reflected at angles.
So, areas away from the sensor's line of sight to light sources may appear darker. Predictably, the sensor's readings will be influenced by the distribution of light and the positioning of obstacles within its direct line of vision.