PURPOSE: To automate fully exposing conditions by processing arithmetically the image signal inputted to a photoelectric conversion camera by an image signal processing circuit.

CONSTITUTION: A photoelectric conversion camera such as a solid state image pickup (CCD) camera 9, etc. is disposed in the lens position of a process camera, etc. The conditions of the original itself such as original density or the like as well as the illuminating conditions such as illuminance distribution and intensity of light source, etc. on an original surface are detected as electrical signals by the camera 9. The highlight point and shadow point in the desired trimming region of the original are found and various conditions for exposing are calculated and measured with a CPU16. The conditions for exposing which are previously set by the operator based on his own experience are fully automated.