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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

Accumulative density is a term you might not recognize. It represents a way we can effectively measure, evaluate, and control color. And although many color experts mean well when they say density is not color, you will discover that accumulative density is color and is a serious tool that screen and digital printers can use to manage color in prepress and production. This article will explain accumulative density in detail and provide information about how to use it in assessing gray balance, four-color-process prints, ink hue, and substrate color.

What is accumulative density?

To accumulate means to grow by gradual additions, and density—in this context—refers to a translucent medium’s degree of opacity. Both definitions are very accurate descriptions of this exciting method of quantifying and managing process-color printing. We print with translucent colors in four-color process. Some people say we print with transparent colors, but we don’t. The difference is translucent means to allow light to pass through diffusely, so that objects on the other side cannot be seen clearly. Transparent means allowing light to pass through with little or no interruption or distortion, so that objects on the other side can be clearly seen.

Consider the following example. Because our four-color-process inks are translucent, printing yellow over magenta results in red. This is an accumulative result of yellow and magenta. If we print cyan over magenta, the result is blue—or the accumulative result of cyan and magenta (Figure 1). Of course we can measure the result with a spectrophotometer and compare the result to a color target and calculate a delta E. But why not convert the values to density using the same data? Would that be more understandable to a printer who’s working in CMYK? The answer is yes. It is also why we need to understand how accumulative density works.


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