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Accumulative Density: A Powerful Color-Control Tool

(July 2008) posted on Tue Jul 15, 2008

The concept of accumulative density may not be familiar to you, but acquainting yourself with its many benefits can enable you to manage color in some very challenging situations. Discover how to integrate this potent ally into your workflow.

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By Mike Ruff

Here’s how it works. The objective in producing any color image is to print the image with no cast. If we accomplish this task, then we’ll have accurately represented the original file. We don’t have to have a client’s proof to know, or prove, that the print is accurate. We only have to show that we have not added a blue cast, a red cast, a green cast, or a yellow cast to the original. Neutral-gray-print production is critical to confirming that the result of our print is accurate. Our lives in the print world become clear and meaningful when we grasp this concept. Those who fail to learn this may live their days mired in subjective opinion and unclear objectives.

We all say we know neutral gray is important, but how do most people judge neutral gray? I submit that most people simply look at the gray. They use the world famous chin-o-meter as they stand on one foot with their left hand on their chin and say to themselves, “Self, I believe that is neutral gray.” What I find is most of the time they are dead wrong. The reason I am bold enough to say that is because I evaluate proofs at different graphics-production facilities every week. Most of the time the neutral gray that they are professing to use is actually blue cast—and most of the time it is blue cast because it’s missing yellow. Using the spectrophotometer in the All mode quickly verifies whether a gray is neutral or has a cast in it. The device’s findings are not subjective opinions.

Accumulative density confirms neutral gray (Figure 3) via the spectrophotometer in the All mode, which reads a gray patch that is built from C, M, and Y. You can verify neutral gray when the density values of C, M, and Y are equal. Notice in Figure 3 the C, M, and Y, are perfectly balanced on the left, but the blue-cast gray on the right is missing some yellow. You can see shifts in as few as two points, but they’re normally not noticeable. Shifts of more than three points become noticeable and objectionable. You’d be very quick to detect five points of deviation visually.


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