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FLEXO Magazine : September 2010
Technologies & Techniques Image Optimization Cut ink usage and improve Print quality By Mike Ruff SincetheSpringof2008,theprintingindustryhasbeen buzzing about the words image optimization. In this short article, I hope to impart an important understand- ing of what the fuss is all about and how legitimate it is. Those that have taken time to investigate image optimization are seeing an increase in productivity and much-needed profit margins in all types of printing—offset, digital, flexo and screen print. This is a new technology, not some old or re-invented prod- uct. However, just like a great song that comes along every decade, some old products with similar characteristics claim to “do the same thing.” They don’t. I hope to show an example of the new technology and encourage you to get moving on printing better, printing more accurately and saving a lot of ink at the same time. Image optimization will do that for you if implemented properly, and if you do not get sidetracked by products that appear to be the same thing but are not. A BrIef explAnAtIOn Image optimization is not the same as ink optimization, although they both save ink. The primary difference is that image optimization improves print accuracy; ink savings is a side benefit. On the other hand, ink optimization has been around for years in the form of GCR (gray component replacement). In process color printing, when the three chromatic colors, CMY, overlap they produce black. (Really, it is dark gray.) This is called the “gray compo- nent.” Some people a lot smarter than me figured out that most of this “gray component” could be replaced using a black dot, thus saving three colors of ink and increasing only one—black. This is saving ink. Our industry also found that by using heavy GCR, color was much easier to control on press. GCR immediately found a home on flexo and screen printing presses. However, the euphoria quickly waned as less knowledgeable prepress people overused GCR and produced questionable results, such as grayed-out shadows, hard breaks in flesh tone shadows, black trees, black purples and auburn hair turning black. The problem with heavy GCR is it is a non-colorimetric creation of a black channel, causing unwanted color shifts in certain color combinations. The result in some images was good, but in other images it could be a disaster. Some prepress people went off the deep end the other way and stopped using GCR in any form. They said, “We only use UCR (under-color removal).” Of course, this was an over reaction because UCR and Light GCR were almost identical. UCR is an even less sophisticated way to create a black channel than GCR. If you look at Figure 1, you can see UCR and light GCR are comparable. A slight edge is given to light GCR because the black channel is smoother. Since the early days of using heavy GCR to control color shifts on press, really good prepress people in the flexographic industry have learned to use GCR in Photoshop in very creative ways, including creating several layers in an image. They would mask out ar- eas that excessive GCR would destroy, and only use heavy GCR in the layers where it would work well. They used light GCR in layers that are prone to col- or shift. Then they simply re-assembled multiple layers and flattened the image. It’s beautiful to see the skill of some of these craftsmen as they make life good for the pressman. Highly skilled prepress technicians still use selective GCR and have mul- tiple levels of GCR in the same image. This manual method is used regularly in flexography and screen printing. The problem with manual selective GCR is, it is slow and the manipulation of the color is still not colorimetric. There are about 20 manual steps required in each image. It looks good, it prints great and the ink savings are there, but it takes a very expensive prepress person about a half an hour to prepare one image. AddIng gCr tO A rIp RIP manufacturers soon decided they could add ink optimization modules to their RIPs and save ink. The modules just linked the image to a higher amount of GCR. It worked for ink saving and it helped in press control, however, the www.flexography.org sePteMBeR 2010 FLeXO 65 Your package has only three to six seconds to grab the consumer’s attention... 800.346.8570 www.colorresolutions.com FLX_Sept2010_mech.indd 65 9/2/10 12:42 AM