An exterior heat insulation panel is disclosed which uses vaporization heat of water. To this end, the method includes determining, in dependence on the distance of the first color co-ordinates from the boundary, an extended part of the boundary of the color range and establishing the second color co-ordinates on the basis of said extended part of the boundary. Opening energization is applied to the motor in order to allow the shutter blade to pre-perform an opening motion before performing a closing motion whenever a still image is photographed.