Job Design
As described by Bob Coomes, the project committee decided to print three separate items (“coffee,” “dog” and “kebab”) with two different color reproduction schemes (CMYK plus spot, and EG). But the design of the EG items was exactly the same as the design of the CMYK plus spot items. A job designed as spot colors should be able to be converted to either 4-color or 7-color given accurate press profiles and good job conversion prepress tools.
The three items in Figure 2 were designed by Venn49 Creative Lab—the sister design firm of The ALC Group who did all of the prepress as a contribution to FTA. The total design had 22 colors (CMYK plus 17 spot colors and white). Looking ahead, these 22 colors were to be printed at PPT on a 10-color CI press. For the CMYK plus spot item, images were to be left as 4-color, two spot colors (Pantone 185 C and Reflex Blue C) were to be left as spot colors, and all remaining spot colors were to be converted to CMYK based on the 4-color profile of the press. For the EG items, all colors (process and spot) were to be converted to 7-color based on the 7-color profile of the press.
Image Conversion Settings
CMYK images were left as CMYK but converted to 100 percent Gray Component Replacement (GCR) based on the CMYK press profile. The intent was to have a fair comparison between the 4-color images and the 7-color images (which were converted with 100 percent GCR based on the 7-color press profile). We decided to expand the images converted to 7-color, arguably making the comparison “unfair.” The logic was to simulate how images would be converted on a “real” 7-color production job.
As more and more users of EG are applying it to images as well as to spot colors, we chose to apply it to images on the 7-color items for this job as well (see Figure 3). To make the comparison less bias toward 7-color, we used an image conversion Adobe Photoshop plug-in that employs a patented technology called “user adjustable gamut expansion” and chose fairly conservative settings to achieve printed images with significantly less-than-maximum gamut expansion.
Full Job Conversion
For simplicity, the complete job—CMYK images as well as spot color vector—was converted with the click of a button in a well-known packaging graphics editor. The Photoshop plug-in conversion settings described above were saved and applied in the packaging graphics editor. This editor (depicted in Figure 4) converts images and spot colors based on the profile of the press. For the CMYK plus spot color items, the 4-color press profile was used. Pantone 185 and Reflex Blue were set to “do not convert”; the remaining 15 spot color were converted to CMYK. For the EG items, the 7-color press profile was used. All colors were converted directly to the 7-color press profile.
One might note that six of the 10 colors in the “kebab” job were greater than 1 Delta E (00) out of gamut. The new “in-gamut” color is known as the “dependent aim.” A major benefit of EG is that we can access the exact L*a*b* values of every depended aim color as soon as we have a press profile. We do not have to wait until the production job is printed to know the result. The goal of the production job is then to match the “dependent aim,” not the “master standard.”
Screening
Recall that the optimum screen was found using the single-color target run as part of the optimization process. This screen is now selected along with the curves and other parameters to RIP the job. The result is a set of LEN files which are similar to one-bit TIFF files, but are optimized for a specific supplier’s digital imaging device. The graphics in Figure 5 show a comparison of the HD flexo screen used for this job to a traditional AM screen.
Plate Imaging & Exposure
The last step in prepress was to image plates. This job consisted of 10 plates (one for each color) at the full job size (21-in. x 42-in.). Plates were imaged at 4,000 dpi and exposed in a controlled nitrogen exposure unit to achieve a flat top dot.
The flat top (effectively 1:1) plate exposure enabled the very small min dots shown in the HD flexo hybrid screen. As an aside, it might be noted that plate exposure is currently an area in flexography where huge quality strides are being made. Nitrogen chamber plate exposure has helped the industry make large gains in quality. Looking forward, moving source LED (MS LED) plate exposure is proving to show even greater quality gains—enabling smaller and more isolated minimum dots than any technologies to hit the market to date.
But regardless of the plate exposure technology used, it’s the complete package—screening, plate imaging and plate exposure—and the concept of optimizing these variables together with FIRST recommendations that produces the highest quality. This project shows just how high the quality of nitrogen chamber exposed plates can be if optimized along with the other relevant variables.
The Final Pressrun at PPT
There were many people and companies involved in this project, but if I were to award an MVP, it would go to PPT (with a very close runner-up award going to The ALC Group). It may seem odd that The ALC Group gets all the press (everything described here was done at their facilities) while MVP PPT gets only this small paragraph. The moral of the story: A printer’s job, when done correctly, should be boring! Their only job in production is to print the same way they printed during the characterization pressrun. How boring, but how profitable!
Although this overview article is light in pressroom specifics, forthcoming articles in this series will go into greater detail on each of the FIRST steps and will dig deeper into the details of the pressroom. The last article in this series will show the quantitative data of how closely PPT printed to the numbers. Can we really print to FIRST numbers? Stay tuned.
About the Author: Mark Samworth began his career with DuPont, where he held numerous positions in the areas of flexographic plates and electronic imaging. Mark joined Esko in 1997 and is currently focused on consulting in screening, calibration, G7, color management and expanded gamut. He holds 11 patents in digital imaging, including FlexoCal, Hybrid Screening, Plate Cell Patterning, Concentric Screening, Equinox expanded gamut technology and PressSync. He has authored numerous articles in the industry’s major trade publications and presented many papers at the industry’s major trade forums. In May of 2011, Mark was inducted as the 49th member of the FTA Hall of Fame. Mark received his bachelor of science from RIT and his MBA from the University of Delaware. He lives in Wilmington, DE.