Gray balance is the proper percentage of combinations of cyan, magenta, and yellow inks that produce neutral shades of gray. Hue (color) shifts will occur when there is any imbalance of one of the components. It is necessary that every printer determine their gray balance for each combination of these components at specific line rulings. This is obtained by using gray balance targets as shown left and right. The targets represent only a few different dot percentages, a chosen highlight (HL), midtone, and shadow dot (SH). Note: More gray balance blocks can be used for a fingerprint. The actual number of blocks used depends upon how much information is needed about different neutral gray dot percentages.
Using a densitometer, a neutral gray patch for each dot percentage can be recorded. This information is then used by the prepress department to set neutral gray control points for each halftone image. Knowing the neutral gray control points will ensure more consistent gray balance in printed reproductions.
The gray balance will vary for each different ink set as well as the same ink set over time. Therefore, it is recommended that the prepress department develop an upper and lower control limit around the average gray balance infor-mation. This will be the range the pressman must fall within while printing. It is further recommended that gray balance tests be repeated over time with the same ink set if it has not been used for an extended period of time.
1. Romano, Richard & Frank: The GATF Encylopedia of Graphic Communications,GATFPress, 1998: p. 368-9.
