Image Number 8 for United States Patent #6788431.
A patch image for calibration information is printed and exposed onto a film in advance and the image is formed in the same way as a frame image by heat development processing. In a case in which an image data input to a data sorting portion is determined to be a patch image, the data is transmitted from the data sorting portion to a correction value operating portion and a curve (.gamma. curve) of exposure to be referenced and a .gamma. curve based on the read patch image are compared. Then, correction is operated and the corrected value is transmitted to a data converting portion. The image data of each frame is corrected in accordance with the correction value.