A camera includes a light emitter, a light detector, a clamp circuit, a calculator
for outputting an output ratio signal, a converter for converting the output ratio
signal into a distance signal corresponding to the distance or a predetermined
fixed value, a light meter for measuring the luminance of outside light, and an
exposure control that, when the luminance of the outside light measured by the
light meter is lower than a predetermined switchover luminance, controls the aperture
of the camera lens to a released aperture value, and when higher than the predetermined
switchover luminance, controls the aperture of the camera lens to increase corresponding
to the luminance. A first auto-focus (AF) signal value corresponds to an infinity
determination distance and a second AF signal value corresponds to the switchover
luminance. The AF signal value, which corresponds to the shorter range, is set
as an infinity determination threshold value.
