Exposure control method and apparatus for photographic printer

An exposure control apparatus for a photographic printer, said photographic printer having a light source and yellow, magenta, and cyan color-correcting filters which are inserted in between said light source and a frame of developed photographic film, said photographic printer also having a controller for setting said color-correcting filters in respective filter positions to adjust three-color components of printing light from said light source, said photographic printer printing said frame on photosensitive material, said exposure control apparatus comprising:

• a photometric section for measuring a frame to be printed photometrically in three-color separation, to obtain a photometric density thereof for three primary colors;
• a domain selector section, provided with said photometric density of said frame, for generating a signal representing one density domain in response to said density of said frame, wherein said one density domain is selected from a plurality of preset density domains that divide a three-dimensional density space, and wherein said density space is defined by coordinates at which respective photometric densities of said three primary colors has been taken;
• a matrix element memory for storing data of matrix elements, said memory having addresses corresponding to said plurality of density domains, each of said plurality of density domains having respective ones of said matrix elements;
• an element selector section, provided with said signal representing said one density domain, for accessing said matrix element memory at one of said addresses that corresponds to said one density domain, to identify selected ones of said matrix elements corresponding to said respective matrix elements of said one density domain;
• and
• a matrix operation section for executing a matrix operation in accordance with said photometric density of said frame and with said selected ones of said matrix elements, to obtain said respective filter positions at which said printing light is optimized.

An exposure control method of a photographic printer comprising the steps of:

• defining a three-dimensional density space by exposure amount coordinates of three primary colors of a printing light;
• dividing said three-dimensional exposure amount space into a plurality of exposure amount domains;
• determining respective matrix elements for each of said plurality of exposure amount domains;
• obtaining an exposure amount of a frame to be printed, said exposure amount being calculated from a result of photometrically measuring, in three-color separation, said frame to be printed;
• selecting one of said plurality of exposure amount domains in accordance with said exposure amount of said frame to be printed;
• selecting said respective matrix elements of said selected one of said plurality of exposure amount domains;
• executing a matrix operation in accordance with said exposure amount of said frame to be printed and with said selected respective matrix elements to determine, for cyan, magenta, and yellow filters, respective positions at which said printing light is optimized;
• and
• inserting said filters between said printing light and said frame to be printed on the basis of said respective positions to adjust components of said three primary, colors in said printing light.