Digital process sensitivity correction

A method for producing photographic images from a negative working photographic film strip, of the type that uses density values of the photographic film strip to determine the density values of the produced photographic images, the improvement comprising the steps of:

• a) forming at least two reference patches of differing exposure conditions onto an otherwise unexposed portion of the photographic film strip prior to photographic processing, each reference patch falling within the total scale of the photographic film strip;
• b) photographically processing the photographic film strip to form densities corresponding to the photographic images and said reference patches;
• c) scanning said processed photographic film strip to form density representative digital signals corresponding to the photographic images, said reference patches, and an unexposed region of the photographic film strip;
• d) obtaining standard film density values representative of the photographic film strip;
• e) calculating gamma correction values from said density representative digital signals corresponding to said reference patches and said standard film density values;
• f) utilizing said calculated gamma correction values, said density representative digital signals corresponding to the photographic images, said density representative digital signals corresponding to the unexposed region of the photographic film strip, and said standard film density values to form corrected density representative digital signals;
• and
• g) utilizing said corrected density representative digital signals to produce photographic images from the images recorded on the photographic film strip.

A method for producing photographic images from a negative working photographic film strip, of the type that uses density values of the photographic film strip to determine the density values of the produced photographic images, the improvement comprising the steps of:

• a) forming at least two reference patches of differing exposure conditions onto an otherwise unexposed portion of the photographic film strip prior to photographic processing, each reference patch falling within the total scale of the photographic film strip;
• b) photographically processing the photographic film strip to form densities corresponding to the photographic images and said reference patches;
• c) scanning said processed photographic film strip to form density representative digital signals corresponding to the photographic images, said reference patches, and an unexposed region of the photographic film strip;
• d) obtaining standard film density values representative of the photographic film strip;
• e) calculating gamma correction values from said density representative digital signals corresponding to said reference patches and said standard film density values;
• f) calculating speed correction values from said density representative digital signals corresponding to said reference patches, density representative digital signals corresponding to said unexposed region of the photographic film strip, and standard film density values;
• g) utilizing said calculated gamma correction values, said calculated speed correction values, and said density representative digital signals corresponding to the photographic images, to form corrected density representative digital signals;
• and
• h) utilizing said corrected density representative digital signals to produce photographic images from the images recorded on the photographic film strip.

A method for producing photographic images from a negative working photographic film strip, of the type that uses R, G, and B, density values of the photographic film strip to determine the R, G, and B, density values of the produced photographic images, the improvement comprising the steps of:

• a) forming at least three reference patches of differing exposure conditions onto an otherwise unexposed portion of the photographic film strip prior to photographic processing, each reference patch falling within the total scale of the photographic film strip;
• b) photographically processing the photographic film strip to form densities corresponding to the photographic images and said reference patches;
• c) scanning said processed photographic film strip to form R, G, and B, density representative digital signals corresponding to the photographic images, said reference patches, and an unexposed region of the photographic film strip;
• d) obtaining standard film R, G, and B, density values representative of the photographic film strip;
• e) calculating a gamma correction matrix from said R, G, and B, density representative digital signals corresponding to said reference patches and said standard film R, G, and B, density values;
• f) calculating R, G, and B, speed correction values from said R, G, and B, density representative digital signals corresponding to said reference patches, R, G, and B, density representative digital signals corresponding to said unexposed region of the photographic film strip, and said standard film R, G, and B, density values;
• g) utilizing said calculated gamma correction matrix, said R, G, and B, density representative digital signals corresponding to the photographic images, said R, G, and B, density representative digital signals corresponding to the unexposed region of the photographic film strip, and said standard film R, G, and B, density values to form corrected R, G, and B, density representative digital signals;
• and
• h) forming R, G, and B, channel independent density representative digital signals from said corrected R, G, and B, density representative digital signals;
• i) forming R, G, and B, log exposure representative digital signals from said R, G, and B, channel independent density representative digital signals;
• j) utilizing said R, G, and B, speed correction values and said R, G, and B, log exposure representative digital signals to form corrected R, G, and B, log exposure representative digital signals;
• and
• k) utilizing said corrected R, G, and B, log exposure representative digital signals to produce photographic images from the images recorded on the photographic film strip.