Hal Hinderliter

Compensate for dot gain?
November 20, 2007

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Question: How should I compensate for dot gain with our new CTP system?

Answer: To address this commonly misunderstood topic, here is an excerpt from Chapter 2 of my new book for the Newspaper Association of America (available in 2008), the NAA CTP Calibration Guidebook:

Now that prepress production has become digitized, many participants in the process seem to think that computer-to-plate systems (or even imagesetters) should be adjusted to lighten every tint value enough to eliminate the impact of dot gain, in effect using the prepress department to compensate for the tone value increase that occurs in the pressroom. Sadly, here’s the straight answer: dot gain compensation is a function of the design process, not prepress.

Why not compensate in prepress?
That may seem strange, especially if you share the prevalent prepress attitude that designers are ill-educated "creatives" who don't fully understand the printing process. Even if your views are not so cynical, however, you might wonder why the prepress department's sophisticated “power users” with their souped-up Macs and expensive software programs would rely upon the designer to compensate for dot gain?

The simple answer is, because that's how it's always been.

Unfortunately, the printing industry is full of less-than-optimal workflows created by our slow emergence from the past. Prior to the late 1980s, no one used a computer to design a page layout. This meant the designer was not able to view an instantaneous rendition of his/her design in full color on the computer’s monitor. In the days before desktop publishing, the designer would choose a background tint of 30 percent cyan not because he liked the way it looked on his monitor but because he had seen a printed sample of what 30 percent cyan looks like when reproduced by a printing press on a particular type of stock. In other words, choices were based on the experience of previous print runs, not on a monitor.

The potential danger of prepress dot gain compensation
Attempting to change this paradigm now would have an enormous impact. Jobs that were prepared the “old way” would suddenly be dramatically lighter on press, with washed out images. Supplied ads would not reproduce as intended by the advertising agencies who created them. Worst of all, the prepress department would have to compensate differently for each type of paper or brand of ink, leading to a nightmarish mixture of possible outcomes.

Fortunately, this is not how the process works. Instead, dot gain compensation is "applied" by the designer through the selection of appropriate color values based on an inherent knowledge of the reproduction process – not by specifying colors that appear pleasing on-screen, then expecting the output device to adjust that value before it hits the press. Designers who are interested in seeing an accurate representation of a color’s printed value on their monitor should use color management to make the monitor imitate the press, not the other way around.

Soft proofing = visual compensation during design
Color management has improved to the point where a properly calibrated high-quality monitor combined with an accurate printing press profile and properly configured software applications can provide an accurate on-screen preview of the press reproduction (including the dot gain). In other words, you choose 50 percent in your InDesign document but you see a 75 percent tint on your monitor (assuming 25 percent dot gain on press). Designers who are interested in this advanced workflow (commonly known as “soft proofing”) are free to invoke it at any time, without fear of consequence to the rest of the print reproduction system. 

Posted by Hal Hinderliter on November 20, 2007 | Comments (0)