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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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First of all, to measure accumulative density you need a spectrophotometer that collects information in the form of spectral data. The spectrophotometer collects the data by transmitting light to the substrate, measuring reflected light, and then reporting its findings in L*a*b*, L*C*H*, XYZ, or in density. If we want to know the density, the default of the device is to report the dominant spectral response in a density equation. One important bit of information to take note of here is that the same data are used to calculate density, as well as L*a*b*, L*C*H*, or XYZ values. Therefore, to say density is not color shows a lack of understanding that the collected information is the same, but simply reported in a different form.


Setting up the spectrophotometer

All modern spectrophotometers come out of the box with a density default setting in the Automatic mode. That means when you read density in this mode, the response is the dominant spectral value reported as C, M, Y, or K (Figure 2). However, most modern spectrophotometers also have an option of viewing all of the spectral values of C, M, Y, or K. I leave my device set up like this most of the time because I want to see all of the values, not just the dominant density. So the first order of business to use accumulative density is to set up your spectrophotometer to report all of the colors. You’ll be ready use accumulative densities once you’re able to read a color and see all the densities.


Accumulative density in gray balance

Gray-balance evaluation is another extremely valuable use of this powerful measuring method. As you know, the objective of print production is printing a client’s file accurately. But many times we don’t have an accurate proof or even a proof at all. The client just gives us a file, slaps us on the back and says, “Have a nice day, but if you goof up my art, I’ll kill you.” The power of accumulative density can solve the problem of knowing a print is accurate to the file without a proof.


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