PURPOSE: To keep the display state of a monitor picture at a fixed tone and contrast state and to enable picture photographing suitable for diagnosis by using luminance and chrominance, which is obtained by using a reference color setting means, while correcting it to reference luminance and chrominance.

CONSTITUTION: By using a reference color setting jig 68 which is simple and easily fitted only by covering the tip part of an endoscope 3, a signal to be a standard is applied to the monitor picture of a photographing device. By using the picture, the chrominance and luminance on the monitor picture is measured and while comparing the reference chrominance and luminance stored in a reference color chrominance and luminance storing means 66 with the measured chrominance and luminance by a reference color comparator circuit 67, an input to a monitor is corrected. Thus, the chrominance and luminance on the monitor picture can be kept at a fixed value regardless of the kind of an input signal source and further, based on the measured luminance, the exposure amount of a still camera can be controlled. Then, the dispersion of a picture to be obtained can be decreased.