Printed Proof
The 2017 FLEXO Magazine Cover Project—showcased in the October issue—featured a cover spread printed flexo and digital to showcase the 2017 FTA Technical Innovation Award winners. The outside spread was printed on a hybrid press (the FLEXO masthead was printed flexo, while the rest of the spread was printed digital); the inside spread was printed entirely flexo. As such, there were two full pages—an Esko ad and a Flint Group ad—in which to showcase the ability to print “non flexo-ized” CMYK separations. This is a true test of the ability to print separations with dropouts “everywhere” containing isolated dots throughout every color in every image.
The image of the dancers in the Flint Group advertisement shows MS LED-exposed plates can enable offset separations to be printed flexo—without a single alteration for the flexo process. The Flint Group marketing department submitted the image as a JPEG RGB file embedded in a PDF with the understanding that, once approved, they would convert to CMYK, “flexo-ize” the separation, then re-submit. As might be expected of an offset JPEG image, a prepress image quality check for dropouts, isolated dots and scum immediately raised red flags. However, the cover project team saw this as a chance to show off flexo’s capabilities and specifically asked Flint to keep the image “as is.” The only treatment to the image was conversion from Adobe RGB to GRACoL2013 CMYK (also known as CRPC-6) as an automated process in creating the PDF.
Isolated Dots Without Any Sign of Scum!
The close-ups are photomicrographs of Flint Group’s ad that ran on the inside back cover of last month’s FLEXO Magazine. It was printed flexo using MS LED-exposed plates. To see the real print samples, grab a copy of October’s issue and break out your loupe.
You will notice a “shadow” of small and isolated dots around the entire “dancers” image. This is the result of JPEG “noise” being screened, held on plate and printed. Such noise is particularly pronounced around silhouette images and is one of the reasons image files should never be saved in the JPEG format.
But for this demonstration, there could hardly be a better or more challenging image. What better way to showcase flexo technology than to print an image full of dropouts, scum and isolated dots, and achieve a clean printed result in press? The proof is in the print.
Color Conversion & GCR
The Esko advertisement from that issue reveals an even closer look at the future of flexo color separation. No special treatment was performed to “flexo-ize” this image; instead, it was “blindly” converted from Adobe RGB to GRACoL2013 CMYK in Adobe Photoshop. Then—just to show off—we took one additional step that almost no flexo printer would have performed in the past, but which the cover project team believed most flexo printers will routinely perform at some point in the future: We converted this image to 100 percent Gray Component Replacement (GCR). Hence, an image that in the “old days” would have had dropouts only in black now has dropouts everywhere, in every color (cyan, magenta, yellow and black).
GCR images reduce ink consumption, but more importantly, have extreme stability on press. Even the best flexo and offset printers have trouble printing a 50-C, 40-M, 40-Y as a consistent, neutral gray. Why fight it when it can be convert to a stable 5-C, 4-M, 4-Y, 52-K?
Eliminating Partial Dots Through Advanced RIP Technology
As part of the 2017 FLEXO Magazine Cover Project, we’ve proven that with the right conditions (a key one being an MS LED-exposed plate) you can print images with extreme amounts of scum and still achieve a clean printed result.
New RIP technology enables fully automated solutions for eliminating partial dots. The only isolated dots remaining are those of the hybrid screen. Screen 1 contains no re-sampling, Screen 2 uses full re-sampling and Screen 3 uses full re-sampling with partial dot removal.
But does that mean you should? Two new RIP tools offer automated workflow-based approaches to ensure partial dots and small image noise artifacts don’t make it into the final plate. The first is a RIP setting called “re-sampling.” It’s well understood the conflict between image resolution (typically around 300 dpi) and CTP device resolution (exactly 4,000 dpi for high-resolution flexo) can create partial dots that are smaller than the minimum desired dot size in your screen (see Screen 1). Setting the re-sampling control to “output resolution” instructs the RIP to internally increase the resolution of all images to 4,000 dpi.
The result is an elimination of about 80 percent of the partial dots—as well as an increase in the smoothness and roundness of all dots in the image (see Screen 2). But even after this—depending upon the specific image—a few partial dots may still remain. A second post-RIP control called “clean highlights” allows the user to set a minimum dot size (set at 16 pixels in Screen 3). The automated task then cleans all dots below this size on the screened file.