A sensor may detect glare from a recorded image and a shade position of a motorized window treatment may be controlled based on the position of the detected glare in the image. A luminance of a pixel may be calculated in an image and a glare condition may be detected based on the luminance of the pixel. For example, the sensor may start at a first pixel in a bottom row of pixels and step through each of the pixels on the bottom row before moving to a next row of pixels. When the sensor detects a glare condition, the sensor may cease processing the remaining pixels of the image. The sensor may calculate a background luminance of the image by reordering the pixels of the image from darkest to lightest and calculating the luminance of a pixel that is a predetermined percentage from the darkest pixel.