This article will explore how to harness neutral gray to benefit print production.
By Mike Ruff
The answer actually started with GRACoL in 1996. GRACoL defined gray in L*a*b*, not by TVI values. This was huge, but there were still some problems that had to be solved. G7 (not to be confused with GRACoL 7), developed by Don Hutcheson and IDEAlliance, solved the problem by specifying neutral gray and creating a Neutral Print Density Curve Specification. I personally have witnessed print facilities going from an average setup time of three hours to 45 minutes by just calibrating and training press operators to print to G7 neutral gray. Isn’t it amazing that such a simple process—one the we’ve had under our noses since color separation began—could move our industry so far so fast? That’s the power of neutral gray on press.
How to print neutral
The first step in printing to neutral is learning to measure and know when you have arrived at a targeted neutral gray (Figure 5). GRACoL defined neu-tral on grade 1 and 2 paper. This paper is very white and normally doesn’t have very much of a color cast. Technically, midtone neutral in L*a*b* is L*50, a*0, b*0. However, visually we do not accept this. In my opinion, we have come to think that neutral gray must be slightly cool because it is the ugly stepsister of blue. I’m fine with that as long as it is documented as a specification I can point to and know when I have attained it.
True visual midtone neutral gray is documented by GRACoL 7 and specified by G7 as L*59, a*0, b*-1. G7 specifies neutral gray tones at the 25% area known as the Highlight Contrast (HC), the Highlight Ranges (HR) and the Shadow Contrast (SC) (Figure 6). What is amazing is when I attain this and then measure the color in All Densities mode on a calibrated densitometer, the C, M, and Y are almost identical. These results confirm that what I have is neutral and is not adding a color cast to the image. No C, M, or Y value overpowers the other colors. The standard viewer would have a difficult time seeing any specific color cast in the gray if they were evaluating it in standard viewing conditions.
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