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Zeroing in on New Ways to Match Color

(July 2008) posted on Thu Jul 24, 2008

Visually judging the accuracy of color between printed samples is a process that many printers use. Unfortunately, this method leads to downtime and waste. Here you


By Bruce Ridge

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The likelihood of any printer involved in reproducing color to actually reproduce a color exactly is quite low. And it’s even more unlikely that they’ll be able to do so on a repeat basis. According to benchmarking conducted by Nazdar Consulting Service on screen presses and digital printers, most printers tragically set a Delta E (a measure of color variation between samples) target lower than what their presses can accommodate. So setting a tolerance for reproducing color goes way deeper than picking a number that keeps you on a par with your competition. Tolerances should be established and set for your equipment, people who approve color, and the requirements of the product being printed.

 

The practice of color tolerancing

So this is where tolerancing comes in to help us. Since we know we cannot reproduce something exactly each and every time, we work towards manufacturing things within certain accepted tolerances. This holds true for all manufacturing. It is necessary to establish these tolerances based on what is acceptable to the buyer, what is necessary to the function of a product, and what the production equipment can achieve consistently and profitably. Tolerance is how much deviation you permit from a standard. The printing world maintains industry-wide tolerancing numbers for the reproduction of perceptual/process-color images, as well as for spot colors like Pantone colors.

Let’s take the case of perceptual/process-color images. Most color printers use some form of color proofing to predict what color will look like once the image is on press. That proof may be built around SNAP, GRACoL, SWOP, or G7 specifications—all of which have particular tolerances for manufacturing flexibility. For example, a SWOP proof may have a targeted solid ink density for cyan of 1.35 on proof and press. But in the fine print the specifications also say there’s a ±0.05 tolerance for the solid ink density for the cyan on the proof and a ±0.10 tolerance for solid ink density of the cyan on press (Table 1).


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