CTP for Four-Color
A review of the technology today, and a preview of trends for tomorrow
By Danny O. Snow
* reviews computer-to-plate (CTP) technology;
* discusses its use in four-color printing;
* offers tips on how to get the best results using CTP; and
* previews future developments.
The methods printers use to put words and four-color images on paper have changed dramatically in the past few years. New digital methods have largely replaced traditional processes that involved art boards, cameras and film.
Computer-to-plate (CTP) technology allows the transfer of digital files from computers directly to printing plates. Most CTP systems start with a computer file created in Quark, Pagemaker, InDesign or another format. The file is then output through a Raster Image Processor (RIP) to a printing plate. This process streamlines the traditional printing process, eliminating the need for camera, film and darkroom.
George Whalen, spokesperson for Citiplate, Roslyn Heights, N.Y., notes there are three broad classifications of CTP systems: "thermal" or infrared laser-based systems; "visible light" (red, green or blue) laser-based systems; and ultraviolet laser-based systems. The first two types output to special thermal printing plates; the latter burns traditional UV plates.
CTP equipment makers include Citiplate, Creo, Vancouver, B.C.; Heidelberg, locations worldwide; and Presstek, Hudson, N.H., to name just a few. According to Don DeHart, president of DeHart's Printing Services, Santa Clara, Calif., Heidelberg and Germany-based Karat manufacture four-color Direct Imaging presses that also bypass camera and film.
Digital presses such as the Indigo and Xeikon, says DeHart, use a similar process to the one described above, but rather than imaging a plate, they image a photoreceptor belt or other type of transfer material to bring the image to the paper. In most cases (with the exception of Indigo), a dry ink or toner is used instead of traditional offset inks.
Eric Roberts, director of graphic technologies for Lehigh Press, a book cover and jacket manufacturer in Pennsauken, N.J., the advantages of digital workflows include the following:
* reduced steps in workflow and number of personnel;
* potentially faster set-up time;
* no film, processing, chemicals, etc; and
* better registration and dot quality.
But challenges remain, namely:
* the higher prices of thermal plates and platesetters;
* a need for all-digital stripping;
* re-RIPing for changes; and
* obsolescence of previous film, proofs, etc.
While cost considerations generally take precedence in comparing digital and traditional platemaking, quality must be considered, as well. The clearest benefit of CTP in terms of production quality is the way the dot is created. Roberts explains that with CTP, the sidewalls of the dot are perpendicular to the substrate as with a cylinder. (Compare this to a conventional dot, closer in shape to a cone or anthill.) "Regardless of packing on press or other gain issues," he continues, "a thermal dot can better perpetuate a quality image on the press." For the printer, better dots mean better image quality.
How to maximize quality
Most publishers and printers agree that quality is not created at the platesetter, but earlier in the production process. For example, Robert Dainton, technical director of Citiplate, notes, "Much four-color work in books today is 133 line screen or below. This is well within the current technological capabilities of available and emerging ultraviolet platesetting equipment.
"The keys for book printers," he continues, "are getting: (a) maximum CTP speed; and (b) optimum CTP quality without paying an unnecessary premium for a CTP consumable."
Many printers emphasize the importance of accurate calibration between different components of the digital workflow. However, good calibration alone does not insure quality. Roberts cites the following example: "A calibrated proofer won't compensate for DuPont cyan toner that doesn't match what Kodak cyan toner represents."
According to Roberts, publishers should understand what happens to their files after they go to the printer, while printers need to understand what happens to the files before the files arrive. "A better workflow will come from better communication," he says, "not only from better technology."
Although CTP has matured significantly in the last five years, publishers and printers expect a variety of new technological developments in both hardware and software.
Notes Roberts, "The obvious answer is not the output itself but rather the front end. PDF, as everyone knows by now, is the big trend. It won't necessarily augment color quality, but it will expedite file transfer time and RIP time, and ease up file storage requirements. I believe in the very near future CTP and PDF will be attached at the hip like Siamese twins Chang and Eng Bunker of P.T. Barnum fame."
Dainton predicts a broadening of the supply-side of UV CTP platesetters, using new UV laser, laser-diode and mercury-vapor lamp technologies. "This will result in a rich variety of affordable systems that can meet the different page-volume and production needs of book printers large and small," he says.
In addition to CTP systems, Direct Imaging (DI) presses, digital presses and print-on-demand (POD) systems also bypass conventional platemaking. These technologies, although younger than CTP, are evolving rapidly.
For example, this past summer, the first four-color POD systems were being touted by printers such as Delta Direct Access, Valencia, Calif., and DeHart's. All of these technologies use different hardware, yet they're related. "Which process is better?" asks Don DeHart. "You be the judge. Conventional process, CTP and DI processes, web vs. sheetfed systems, and digital presses all have a place. I believe that rather than being competitive, they're complementary. These different systems … offer the end-user the chance to read a book that looks and feels the same, although it was printed on a different system."
For today's publishers and printers, CTP offers the promise of lowering costs while improving quality. Yet to achieve the best results, careful planning and communication between the publisher and printer are essential.
To be sure, effective integration of prepress and production processes can provide significant benefits in streamlining workflows and reducing costs. Related technologies such as DI and POD also can provide efficient solutions for short- and micro-run jobs. In combination, new ways of putting words and images on paper are changing the landscape of publishing.
Author/Publisher Danny O. Snow has been widely quoted about new publishing technologies by major news media. He also is co-author of U-Publish.com, a book about new technologies for self-publishers, written in collaboration with Dan Poynter. More information is available at the Web site: www.u-publish.com
And Speaking of Color ...
Harlequin introduced ScriptProof, a new ScriptWorks edition RIP that generates color-accurate digital proofs from low-cost inkjet printers. The new RIP includes a Java-based graphical user interface and simplified color management capabilities. LAN users can gain full control over how their jobs are printed on a single proofing device, according to Harlequin officials. ScriptProof's color accuracy results from using the same file for proofing as for final output to imagesetter or platesetter. www.harlequin.com
Pantone recently designated Kodak Approval XP/XP4 systems with Recipe Color software as Pantone Calibrated. The designation allows Approval XP/XP4 customers to reproduce more than 1,000 industry-standard Pantone Matching Systems colors, noted Kodak officials. Recipe Color allows spot colors to be produced using process donors. The resulting spot colors are not tint builds; rather, the ink color is actually created within the system. And the technology demonstrates the dot structure of the printed piece on the proof, allowing customers to check color breaks prior to plating. www.kpgraphics.com
Graphic Arts Technical Foundation (GATF), Sewickley, Pa., released a revised edition of The GATF Practical Guide to Color Management (256 pgs.), a guide to integrating color management into a production workflow. Topics covered include basic color theory, traditional closed-loop color reproduction, calibration, and characterizing scanners, monitors and pritners. There's an updated review of hardware, profiles of color management software and much more. Cost: $75 ($55 for GATF members). Call (800) 662-3916, or www.gain.net.
X-Rite, Grandville, Mich., released QuickCal, densitometer technology for on-demand color calibration applications. It's designed to provide calibration of color output devices including large-format printers, proofers and digitally connected color copiers and printers. www.x-rite.com
Studion, New York City, introduced ColorBlade, a plug-in for Photoshop that employs an appearance model to predict and control image color across media, output devices and viewing conditions. You can download a demo version from Studion's Web site.www.studion.com
For More Info: Citiplate www.citiplate.com
Creo Products: www.creo.com
DeHart's Printing Services and Direct Imaging: www.deharts.com
Digital PrePress Newsgroup: comp.publish.prepress
DuPont on Color CTP Proofing: www.dupont.com/proofing/ctp.html
Graphic Communications Association: www.gca.org/attend/2000_conferences/ctp/
Karat Digital Presses: www.karatpress.com
Lehigh Press: www.lehighpress.com
Thermal plates: www.printwriter.com/PresstekQ&A.htm