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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.


By Mike Ruff

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The practical use of this very accurate gray-balance check is for the time when a client says you have not accurately represented an image file in print. You can actually prove that you have accurately produced the file by presenting the evidence of neutral gray on the print’s color bar. Removing the subjectivity of a person’s opinion from the decision-making process allows you to move production forward and boost a client’s confidence. In summary: Use accumulative density to measure, evaluate, and control neutral grays. Depend on it to verify the accuracy of your work. Validating neutral gray is the most useful function of accumulative density.

 

Accumulative density in four-color process

The next very useful application of accumulative density is in the evaluation of four-color-process images compared to a measureable color target. Our measureable color targets may or may not include color bars. If they do, we can read the densities of the targets’ solids and the solids of our print. We can even read the tonal values on the color bars. But we can also read, evaluate, and control the print area through accumulative density.

If, for example, we have a print that is too red when compared to a color target, how should we fix the issue? Most printers would naturally try to remedy the problem by reducing the amount of magenta—the wrong color move. However, accumulative density can show us what’s causing the color deviation. If we measure the spot in the water on Figure 4 that looks too red on the print and compare it to the same spot on the color target, we find that magenta is not the problem. Cyan is the problem, as it’s too low. The spot on the color target measured in accumulative density is C = 1.31, M = 0.81, Y = 0.56, K = 1.03. The very same spot on the print is C = 1.22, M = 0.81, Y = 0.57, K = 1.00. We also find that the solid density on the color bar is the same as the color target, so the problem is certainly not the solid color. The cyan’s tonal percentage is too low, narrowing the issue to a problem in prepress or on press.


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