An image obtaining method includes outputting an image in at least one of multiple image output modes. The multiple image output modes include a full-size mode, a first binning mode, and a second binning mode. In the full-size mode, a first image is obtained according to a first pixel value. In the first binning mode, a second image is obtained according to a second pixel value and a third pixel value. In the second binning mode, a third image is obtained according to a fourth pixel value and a fifth pixel value.