Pushing the Envelope: Wide Gamut Printing with CMYK Inks

By Ron Ellis

Can You Beat the Standards?

               Sheetfed print quality has improved over the last decade for many reasons. Not only has equipment improved, but standards and specifications have provided printers with tools to improve quality. Print specifications and standards such as GRACoL and ISO are designed to provide quality printing results that are sustainable in production through the use of best practices. Simply moving to a print specification such as GRACoL often increases the gamut for ‘uncalibrated’ printers through proper ink targeting. When I asked Marc Levine, Director of Business Development for The Color Management Group for this thoughts on expanded gamut CMYK printing he said, “Before asking yourself if you can beat the standard, a better question is “can I achieve the standard in a consistent, low cost manner”.

This is an important question because more printers are looking for a way to gain an edge over their competitors. In many cases just printing to a specification or standard like GRACoL or ISO would improve their quality and increase gamut. With only 450 G7 Master Printer’s in the US printing to a specification, and not all of these being sheetfed plants, printing to a specification means you are usually printing better than most competitors instead of printing the same as everyone else. Even so, in this competitive print market quality is more important than ever, and better color can make the difference. Targeting the same print quality and gamut as your competitor may not be enough. Despite this few customers are willing to pay for true multicolor print spaces such as Hexachrome. The assumption is that if a printer can expand their colorspace and still use CMYK process inks they will have a tremendous advantage over their competition. Expanding the gamut of your printing process may seem like a low cost way to offer more color, but is it? “The colors we print are specified by print buyers, says Marc Levine. “Are your customers asking you for color outside the standard print spaces of GRACoL and ISO? What happens if you run your pressroom in a way that the print buyer cannot easily specify?”

Methods to Expand CMYK Colorspaces

               One way to expand out gamut is by adding special expanded gamut inks to our CMYK printing machines, but few customers are willing to pay for these special inks. Is it possible to expand the colorspace of a press with traditional inks and tools? Right now expanded gamut printing is a hot topic. Much of this is because new software and hardware gives printers more control over what they print than they have ever had before.

               The conventional wisdom is that by increasing density you can increase the gamut of the printing press. Many pressmen run to low numbers, especially if they have not calibrated to ISO ink specifications. To expand the gamut we need to run even higher and this can mean running inks up to 1.70 or 1.80 density, or even higher. There is a limit because at a certain point the ink becomes dirty and color actually degrades. The trick is to push the ink as much as possible, but to back off as the ink dirties. Doesn’t sound too difficult? If you understand LAB and your ink set then this part sounds easy, although it is more complicated than it sounds. Bruce Bayne, developer of SpotOn! comments, “Actually the printing process is only designed to use a certain amount of ink film thickness (IFT). Too much and you have a soupy mess with ink out of control. Inks are designed to print at a specific density with an IFT between 4 and 6 mils. The only way to effectively “push” ink to higher densities and still maintain balance on press is to mix the ink with a higher pigment load. In the lab they mix ink to have a higher density at the same IFT by adding more pigment to the same amount of ink vehicle (the liquid part, usually soy-based today). Printing at high pigment loads with some inks can cause severe hooking and shrinking of the gamut.”

               So it is clear not every ink can handle this extra density correctly. Once you have located appropriate ink and increased the gamut of your press, what do you do next? One generally accepted answer might be to curve the press, but doing this can reduce the gamut of the press, hence reducing the benefit. A reduction curve can be helpful, but curving to traditional CMYK colors can take you right back to normal CMYK. Instead we want to take the high-density data and characterize and benchmark the press condition. This requires measuring and creating a target characterization set, and verifying that the data is accurate.

Workflow Considerations

               After you have created your target characterization set, workflow considerations kick in. You cannot just throw any file in and expect it to show the benefits of the high gamut target you have created. The key thing to remember here is that traditional CMYK separations aren’t going to get you very far. If you just take a CMYK separation and put it into this expanded colorspace the results are going to be unimpressive. CMYK to CMYK does not lead to great results and in the world of color management it is often considered a bad thing to convert between the same colorspace.

               This color conversion is very important, and involves using software capable of performing the transform. It can be as simple as converting the images in Photoshop, however this will not help with other elements on the pages. Most often these conversions will be done with advanced software that uses device links. “With tools like Alwan CMYK Optimizer, CGS PressMatcher, GMG ColorServer, and FineEye you can improve the quality of your printer – for special printer situations such as wide gamut printing – as well as optimizing your daily CMYK printing.” Marc Levine states. “It is very important to have some tools to help make these conversions.”

To do this conversion we may choose to come from a wide gamut space such as Adobe RGB and convert to our new target space. While this will improve the look of our sheet, for some customers this improvement may not be enough. Regarding wide gamut color spaces Bruce Bayne states, “Actually the vast majority of images fall pretty close to the GRACoL color space unless they have extremely highly saturated colors. So an RGB to CMYK conversion, even to the extended color space will not result in exceptionally brilliant color. Remember the goal of ICC color management is to try and faithfully reproduce the original in a different color space. A normal image then doesn’t instantly become full of brilliant colors.” Because of this we may want to custom separate, correct, and proof images into our colorspace.

To summarize – printing to an expanded gamut on your press requires several things. Not only must the press be able to print to higher densities – but also the files require special preparation to really take advantage of this new press condition. If the resulting new colorspace is not dramatically different from a space such as GRACoL is all this extra work really worth it?

Some Advice for the Uninitiated

               Elie Khoury, of Alwan Color Expertise is a print expert who has implemented wide gamut color reproduction to take advantage of expanded gamuts on conventional as well as waterless offset presses. Elie states, “While high gamut printing is possible especially with Dynamic Color Management technologies upfront like Alwan CMYK Optimizer handling the necessary color transformations, clients need to weigh the costs because it is technically more difficult to achieve and stabilize in production and much more expensive to produce than what is usually expected.”

Elie suggests to keep in mind that the following is needed for a successful expansion of print gamut in production:

1- Specific paper: to avoid ink repulsion at high densities and to have an adequate surface properties (roughness, surface energy…)

2- Specific ink: with adapted tack and viscoelastic properties, together with a short drying time (fast oxido-polymerization for sheetfed inks and fast setting (infiltration) for coldset inks)

3- Minimum ink and total area coverage: you can achieve that for example with Alwan’s Dynamic TAC (minimizes TAC for dark areas) and Dynamic Black/Ink Savings (output CMY minimized for the output process)

4- Press characterization and good averaged ICC profile from various printing conditions

5- Top press minders and/or closed loop systems in order to maintain ink film during the print run

 

The important thing to remember is that no matter what system is being used to separate the files, printing at high densities is not simply a matter of turning up the densities. There are many other mechanical and technical aspects of the process that make it not just normal printing when you are out in the pressroom.

The Importance of Inks?

What about ink? Can high gamut ink help the process? There are a number of high gamut CMYK inks available but they typically cost more, and just like traditional inks they have their limits. For most users the goal would be to use their traditional CMYK inks, and turn them up when printing expanded gamut job. Once the job is complete they simply return to their standard settings. As many users have noticed, just moving ink density up does increase the gamut some and makes the sheet look more vibrant.

Can You Beat the Standard?

               The real question is can you beat a standard? Is it possible to increase your colorspace beyond the standard and print that way day after day? Are the results appreciatively better than the results of printing to GRACoL or ISO? “The standards are pretty good and are there for a reason,” says Dave Hunter or Alwan COlor Expertise. “I would recommend focusing on improving print quality by printing to and optimizing your print characteristics to the standard.”

Conclusions

               The first conclusion is that if you are not already printing to a standard or specification such as GRACoL or ISO you should print to the standard. Before printers invest in the cost of beating a standard they need to invest in achieving a standard. This costs money, but with the resulting improvements it ultimately saves money and improves consistency. This will also likely increase your gamut.

If you are already printing to a standard then the next logical step would be to evaluate and optimize your printing to a standard. Can you achieve the standard on a daily basis? This can be improved with tools for ink optimization, automation, pressroom control, and trending.

The second conclusion is that software alone will not increase your print gamut. Ink, paper, and your print technology all play a vital part in your ability to print extended gamut color. These all add to the expense and complexity of printing.

               Perhaps the most important consideration is the customer requirements. As marc Levine stated, the print buyer is the one who specifies the color to be printed. Printing to a colorspace that can not be easily specified by customers could be put you out of business. The key question here is what are your customers demanding? Are they asking for GRACoL or ISO, or are they telling you they want and are willing to pay for the increased costs that expanded gamut printing requires.

Still Interested in Pushing the Envelope?

What to do if you are interested in trying expanded gamut printing? Contact an expert who has done it before, and despite what some vendors say about easy wide gamut printing – get ready for a rigorous process. With tools like Alwan CMYK Optimizer, CGS PressMatcher, GMG ColorServer, and FineEye you can improve the quality of your printer – for special printer situations such as wide gamut printing – as well as optimizing your daily CMYK printing.

About the Author

Ron Ellis is a consultant specializing in color management, workflow integration, and press calibration. He has provided installation and training services end users, manufacturers, and content creators since 1986. An IDEAlliance G7 Expert and chair of the GRACoL Committee, Ron has performed over 100 G7 calibrations. In addition to calibrating pressrooms for customers such as Pantone, Ron also specializes in creating internal working spaces for brands and agencies that allow them to work more efficiently with vendors, saving both time and money. Ron is published frequently in industry magazines, and has produced training materials for numerous printing industry vendors and publishers. He can be contacted at 603-498-4553 or through his web site at www.ronellisconsulting.com.

 

 

              



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