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Image Enhancement: Better Files, Cost Savings

(February 2013) posted on Tue Mar 12, 2013

Mandel discusses how to conserve ink and make image files easier to print by replacing CMY elements with black.


By Rick Mandel

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In the not so distant past, print providers would assist in preparing the final files we’d use to produce prints. We would maximize the printability as it related to the imaging process. For the last couple of decades, we battled on press to print the files that were provided, because we weren’t willing to take responsibility for altering client files in an effort to improve printability.

Even though modern technology offers avenues to create files that print better, save time and money, and eliminate the need to dig into the files, we still have to deal with situations where a client’s file doesn’t print properly or quickly enough on press. This causes delays on press to achieve the right rendering, which is not always possible, and generates considerable losses in machine time and waste—and client dissatisfaction.

Common issues include mismatches between an incoming file’s color-separation profile and the digital printing device, incompatibility between ink values (total area coverage or TAC) contained in the file and destination printers and substrates, or mismatches between the incoming file’s black generation and printer desired or optimal black generation (GCR/UCR).

Image-enhancement/optimization solutions have created a buzz over the last number of years in the market for digital printing. But what are we attempting to enhance and optimize?

Expectations for optimization
The first impression of the optimization process at a channel or separation level (CMYK) is that the result looks just like under-color removal (UCR) or gray-component replacement (GCR). UCR removes overlapping process colors, replacing them with black ink only during the color-separation process. It is used in four-color (or more) printing.

UCR tends to reduce the volume of shadow color in CMY to allow easier printing and drying. The measurement term that is used for UCR is a total ink-volume limit. Here, 100% of all four colors is 400. If, for example, UCR is called out to be 320, CMY is reduced in a dark shadow and black is increased so that the total coverage of CMYK does not exceed 320%.


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