| 摘要 |
A mid-tone calculator for determining density reproduction to maximize color reproduction in a lithograph tone process. The calculator includes a base having a longitudinal guideway therein, an original density scale thereon and a density compression scale thereon. A lower slide is reciprocally shiftable in the guideway. An upper transparent slide is reciprocally shiftable in the guideway and overlies the lower slide with the slides being shiftable in the guideway with respect to one another. One of the slides has a high density indicator and the other of the slides has a low density indicator thereon. One of the slides has a plurality of tone reference number curves and the other of the slides has a tone intersect line thereon. A transparent cursor is longitudinally shiftably mounted on the base, overlies the slides and is shiftable with respect thereto, and has a half tone placement indicator thereon. Shifting of the slides to produce alignment of the high density indicator with a predetermined high density reading and the low density indicator with a predetermined low density reading on the original density scale will cause the tone intersect line to intersect the tone reference number curves. Thereafter, shifting of the cursor to a chosen point of intersection of the tone intersect line with a tone reference curve will bring the half tone placement indicator into alignment with a reading on the density compression scale to indicate a density for optimum half tone position.
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