A rangefinder provides a rangefinding optical system, and photoreception unit including a pair of photoelectric conversion element arrays, and outputs signals corresponding to the light received by the photoelectric conversion element arrays. The controller allocates the output signals o a plurality of areas, and stores signals included within a single allocated area in memory. The memory has a storage capacity sufficient only to store the allocated data. Data relating to the distance to a rangefinding object are determined by calculations using the data stored in memory.