Abstract: An image capturing device is provided. An image sensor is configured to capture an image of a target at a predetermined time interval according to a target exposure setting, to provide a series of preview frames at a frame rate. A storage device is configured to store each of the preview frames. A processor is configured to access the storage device to obtain first and second preview frames, determine a motion value of the target according to the first and second preview frames, and update the target exposure setting according to the motion value of the target. The image sensor is configured to capture the image of the target according to the updated target exposure setting to provide next preview frame.