Screen Printing - February/March 2013 - (Page 14)

t h e d i g i ta l d i m en si o n IMage enhanceMent: BetteR FIles, cost savIngs Rick Mandel Mandel discusses how to conserve ink and make image files easier to print by replacing CMY elements with black. 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 undercolor 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%. GCR replaces the neutral gray in CMY with black. As in UCR, there are levels of GCR that can be applied to allow the software to alter the imagery into the shadow range. In essence, higher levels have a similar affect as UCR. Black is acting as a real color now and not just shadow detail. So if the black ink has a brownish hue—many digital inks have this issue—the color shift toward a warmer (red/yellow) shadow will occur. Figures 1-3 display a graphic with a skeleton black and optimized with UCR/GCR. The images shown are four colors, CMY colors only, and just the black channel. Data from the shadow and flesh-tone areas in the test graphic are shown in 14 screenprinting Rick Mandel is president/owner of the Mandel Company, a 120 year old, family- owned graphics firm. He is CEO of the Screentech Division, specializing in large-format color separations prepared for the screen printing industry, large-format color separations for the P-O-P industry and large-format digital printing. He has been a speaker for SGIA, SPTF, and POPAI and is a member of the Academy of Screen Printing Technology. He is a 20-year member of SGIA. the shadow area shows: native file—Compensated file with UCr/gCr Cyan 82 37 Magenta 62 20 Yellow 60 19 Black (K) 91 99 the flesh-tone area shows: native file—Compensated file with UCr/gCr Cyan 21 0 Magenta 40 33 Yellow 53 47 Black (K) 0 20 TABLE 1 Data from the test graphics Table 1. The shadow compensation is a classic under-color removal of decreasing CMY and replacing with black. The fleshtone data display GCR’s advantage of replacing the graying component of cyan with black. The goal is for the color to be very similar for each version, though easier to print and with ink-cost savings. L*a*b analysis is a method of measuring color without taking into account the CMYK values. Non-compensated L*a*b of the flesh area is 79, 15, 25. Compensated readings are 76, 15, 28. This is a confirmation of virtually the same color fidelity. UCR/GCR is affecting the TAC. Figure 4 shows simplistically the reduction in CMY and the addition of black. software The producers of image-enhancement/optimization software

Table of Contents for the Digital Edition of Screen Printing - February/March 2013

Screen Printing - February/march 2013
Contents
Editorial Insights
New Products
Increasing Your Profit
Image Enhancement: Better Files, Cost Savings
Prime Prints
P-O-P Primer
Making the Cut
Shoptalk
Industry Update
Distributor/Dealer Directory
Opportunity Exchange
Advertising Index

Screen Printing - February/March 2013