Method of detecting the base concentration of a photographic film

A method of detecting the base concentration of a film comprising:

• a film image entering process of reading a developed film with an image pickup device to generate the pixel values in each of the RGB color component;
• a non-exposure region detecting step of detecting the edge of each frame-image on the film from the pixel values generated in the film image entering process and specifying as the non-exposure region each line of pixels disposed at the intermediate between any two adjacent frame-image edges from the detected edge data;
• and
• a base concentration calculating step of subjecting the pixel values in each non-exposure region specified in the non-exposure region detecting step to a statistic calculation for calculating the base concentration value of the film, wherein
• the base concentration calculating step is arranged to subject the pixel values in the non-exposure regions to two or more arithmetic operations for calculating two or more base concentration value and to judge that the highest of the base concentration value is a true base concentration value.