User login

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

click an image below to view slideshow

 

Item Characteristic
L*
1
a*
1
b*
1
Gloss
%
ISO brightness
%
Mass-per-area
g/m2
Paper type
Gloss coated, wood-free 93 (95) 0 (0) -3 (-2) 65 89 115
Matte-coated, wood-free 92 (94) 0 (0) -3 (-2) 38 89 115
Gloss-coated, web 87 (92) -1 (0) 3 (5) 55 70 70
Uncoated, white 92 (95) 0 (0) -3 (-2) 6 93 115
Uncoated, slightly yellowish 88 (90) 0 (0) 6 (9) 6 73 115
Tolerance +/- 3 +/- 2 +/- 2 +/- 5 - -
Reference paper 94,8 -0.9 2,7 70 to 80 78 150

The interpretation of the number here is that the 93 represents a white value in darkness and lightness. The higher the number, the whiter it is. The a value represents no cast on the green/red axis, and the -3 b reading indicates a slightly blue cast.

So that’s what neutral is, according to an ISO standard. That’s great, but what did the standard do for your understanding of how much cyan and magenta a styrene substrate will add to your print? The substrate’s CMY values are added directly to your print result. Print color is affected more and more as the tonal values move toward lighter tones. Understanding and measuring this effect adds tremendous value in print-color evaluation, as well as developing print curves based on different colored substrates. Therefore, the practical application of accumulative density in paper measurements, evaluation, and color control is troubleshooting and planning in prepress to compensate for the amount a print will be affected by paper color in production.

 

Will your graphics measure up?

Measuring accumulative density helps screen and digital printers control gray value, which is the only way to verify accuracy without a measureable proof. It assists in quick press-control decisions by comparing the printed image to an accurate color target. Accumulative density also takes the L*a*b* mystery out of ink-hue evaluation. Finally, it’ll help you to better understand and control the effects that substrates have on your printed graphics. Your customers aren’t likely to become less demanding any time soon. If you’ve already considered the influence of accumulative density, you’re ahead of the curve. But if accu-mulative density is a new idea to you, now is the time to study it and make it a prominent part of your prepress and production processes.

 

Mike Ruff is chief technology officer of Nazdar Consulting Services, Shawnee, KS. He is involved in training and implementation of color-control procedures for graphics-production facilities. Ruff has actively been involved in the education of screen, digital, and flexo printers for more than 37 years. A regular speaker at industry events and seminars, Ruff is a member of the Academy of Screen Printing Technology and a certified G7 Color Calibration Expert. He’s also certified in flexographic color-management courses at RIT and has authored many articles for trade magazines domestically and internationally. He can be reached at mruff@nazdar.com.

 

 


Terms:

Did you enjoy this article? Click here to subscribe to the magazine.