Abstract: A system that is mounted in a camera capable of focal point detection and that performs correction of the focal point detection data in accordance with the temperature, wherein the temperature inside the photo-taking lens barrel is measured and the focal point detection data is corrected based on the temperature data for the interior of the photo-taking lens barrel. Using this construction, because the temperature of a lens element comprising the photo-taking lens can be accurately measured even where the ambient temperature of the camera has suddenly changed, for example, appropriate correction suitable for the temperature conditions may be performed. Also disclosed is a construction in which the correction of the focal point detection data is performed based on not only the temperature data but also the focal length data for the photo-taking lens.