Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Patent
1980-04-15
1982-07-13
Brown, J. Travis
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
430359, 355 38, 355 77, G03C 504
Patent
active
043395171
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a color correction method for a color printing system, and more particularly to a color correction method in which color negatives to be printed are classified in advance and color correction is conducted in accordance with the classification.
BACKGROUND ART
It has been determined by experiments that, in a large majority of color negatives, the blue, green and red spectral components of the light transmitted through the negative over the whole area thereof are substantially equal to one another, or in a constant ratio (the Evans Principle). Therefore, in most color printing systems, the printing light intensity is adjusted among the red, green and blue exposures on the basis of the red, green and blue large area transmission densities (LATD) of the original to be printed to thereby conduct color correction.
However, in the LATD printing system, the prints obtained are not always satisfactory. For instance, if the ratio of one of the three spectral components of the original to be printed is significantly greater than the ratio of the other two components, color correction based only on the LATD is unsatisfactory.
Such unsatisfactory printing is known as "color failure". When a color negative has been exposed under tungsten light illumination or fluorescent light illumination, the prints obtained are affected by the color of the light source. Moreover, when a color negative is under-exposed or over-exposed, the color balance of the prints obtained is poor because of the reciprocity law failure of the color paper, the shift of the peak of the spectral absorption of the color negative from the peak of the spectral sensitivity of the photo-receptor used in the printer, or the breakdown of the characteristic curve of the color sensitive layer at the high density region thereof.
In the conventional color printer based on the LATD system, the color prints determined to be unsatisfactory have been reprinted at another combination of the color keys selected on the basis of visual inspection by the operator. There also has been proposed a method of color correction in which color negatives are classified based on their blue, green and red large area transmission densities (LATD.sub.B, LATD.sub.G, LATD.sub.R) and the color correction is conducted in accordance with the classification.
The problem is, however, that in the above described method of classification based only on the blue, green and red large area transmission densities, the color negatives cannot be classified into proper groups. For example, in plotting the LATD.sub.B, LATD.sub.G, LATD.sub.R of negatives susceptible to green color failure in a two-dimensional coordinate system wherein one of the axes represents the density difference between the red and green densities and the other represents the density difference between the green and blue densities, LATD.sub.R, LATD.sub.G and LATD.sub.B will fall within a region 1 as shown in FIG. 1. Similarly, LATD.sub.B, LATD.sub.G and LATD.sub.R of negatives exposed under fluorescent light illumination, aged negatives, negatives exposed under tungsten light illumination and negatives exposed under low color temperature natural light in the morning or evening fall respectively within the regions 2, 3, 4 and 5 shown in FIG. 1. As can be seen from FIG. 1, the regions 1, 2 and 3 are partly overlapped with each other as are the regions 3, 4 and 5. Accordingly, it is impossible to clearly distinguish the negatives of the above groups from each other based only on LATD.sub.R, LATD.sub.G and LATD.sub.B.
In order to obtain properly corrected color prints, all the negatives should be precisely classified into groups each consisting only of negatives which can be properly corrected through the same mode of correction. For example, negatives exposed under fluorescent light illumination can be properly corrected by high correction mode, while negatives susceptible to green color failure can be properly corrected by lowered mode correction in which exposures are controlled by a bla
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Brown J. Travis
Fuji Photo Film Co. , Ltd.
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