Workers have found that a split-filter mask made by consecutive exposures through red, green, and blue filters provides better color correction than a mask exposed through a single filter. Nevertheless, split-filter masking has never been adopted in the direct screen separation method. This may be due to the difficulty of determining the opti mum red: green: blue split-filter exposures. This thesis ad dresses the problem of determining the optimum split-filter ratios needed to expose masks for the direct screen sepa ration method. Optimum exposure ratios were determined with the as sistance of a digital computer by systematically trying out 231 different combinations of red, green, and blue exposures using a mathematical model for calculating the effect of split-filter exposures. The computer analysis also provided the required curve shape of the split-filter mask for each separation. It was found that a red-blue split-filter mask and a red-green split-filter mask are sufficient for the green and blue separations respectively. For the red separation, a red-green-blue, three-filter split mask provides improved color correction. The analysis showed that there was considerable latitude in the ratios of the split-filter ex posures. For example, a 15 percent difference in red expo sure in making the mask for the red separation can still yield equally good results. The mask for the red separation was found to have the highest contrast of all the three masks.
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Chen, Jang-fun, "Theoretical determination of optimum split-filter exposures for color-correction masks" (1982). Thesis. Rochester Institute of Technology. Accessed from
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