Systems and methods are provided for detecting an object of object class, such as faces, in an image sensor. In some embodiments, the image sensor can provide a scan sequence that scans a scene over multiple time intervals. The image sensor can scan, in succession, portions of a scene, where each of the portions covers a different amount or location of the scene. This way, the scanned portions can be saved in an image buffer that is sized significantly smaller than an entire frame. In some embodiments, when the image sensor detects the presence of an object of the object class, the image sensor can store positional information (e.g., location and size of the object) in a region of interest buffer. The image sensor can output the positional information to aid an electronic device, such as a camera, perform various functions, such as automatic exposure and color balancing.