In the case where a phenomenon called brightness saturation occurs due to high brightness of light output from a transmission apparatus and high lightness in a portion of a transmitter (light source) within a frame obtained by imaging in a reception apparatus, a decoder in a reception apparatus performs first image processing of shifting the focus by moving a lens in an imager or a filtering process (gradation filtering process) of an image for replacing the color of a brightness saturation area with the color surrounding the brightness saturation area, before determination of a change area, determination of the color of the change area, and decoding of bit string data.