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Do you want dots with that digital proof?

Apr 1, 2002 12:00 AM

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A few years ago, prepress managers and pressroom supervisors chorused “Where's the dot?” when confronted with stochastically screened inkjet proofs. Today, conventional wisdom would have us believe that dots are no longer necessary in a digital proof.

Nonetheless, some are reluctant to part with the direct correlation between dots on a proof and dots on the press sheet. Indeed, as the price of established halftone-proofing systems decrease, the much-maligned rosette is enjoying a comeback.

Some printers purchase these systems at the request of finicky customers, who are concerned that stochastic or continuous-tone (contone) proofs won't reveal potential pattern-interference artifacts in fabric or architectural details. (Pattern interference, often incorrectly referred to as moiré, appears as a vibrating series of wavy lines when details in the original image are captured at a dpi that is too similar to the spacing of the details within the original photograph.)

Other printers opt for a halftone-screened proof because they believe it's easier for a press operator to adjust ink settings, since the comparison between proof and plate is based on a dot-to-dot evaluation.


Is it fair to compare halftone dots to stochastic spots? As a consultant, I often discounted a screened proof's value — until a client asked me to help match a customer-supplied inkjet print. The device was not calibrated to match any reasonable expectation of offset-press reproduction, and the dye set was of the office-supply-store variety. (“SWOP? What's SWOP?” the artist asked.)

Nonetheless, I boldly predicted that after making some Adobe Photoshop adjustments we could be back on press within a few hours. Little did I realize that trying to find a correlation between the coarse stochastic patterns of the consumer-grade inkjet printer and the seemingly microscopic halftone dots of the press sheet would be like the challenge faced by the Allied codebreakers of World War II. Several days and dozens of analog proofs later, we finally achieved an acceptable match.


This experience is supported by GATF's (Sewickley, PA) “2000 Survey on Digital Proofing.” Only 42 percent of the printers surveyed agreed that halftone dots are essential in a digital proof. When these same printers were asked to describe their success rate in matching digital proofs on press, however, a whopping 82 percent of printers using halftone-dot proofing devices said they succeeded at matching digital proofs on press, vs. only 50 percent of printers using stochastic or contone proofs. If we surmise that a higher success rate translates into increased productivity due to shorter makeready times, it may be possible to justify the higher price of halftone-dot-capable digital proofing.

Graphic-arts service providers may also choose digital halftone proofing devices to meet their customers' expectations. For experienced print buyers accustomed to seeing Matchprints, Waterproofs and ColorArts, a screened digital proof provides a certain measure of comfort. According to Jeff Stansil, vice president of manufacturing at Hatcher Press (San Carlos, CA): “All the print buyers we deal with are looking for dots. Not a press check goes by that the customer doesn't grab a loupe and compare the proof to the press sheet.”

A variety of digital-proofing technologies can show dots. Options include laser dye-sublimation, laser ablation, thin-layer thermal transfer, infrared thermal laminate and even high-resolution inkjet devices.


A decade ago, printers offering digital halftone proofs probably used Kodak's Approval proofing device. Most buyers were corporate printers, such as R. R. Donnelly & Sons (Chicago). Even today, Kodak, now Kodak Polychrome Graphics (KPG) (Norwalk, CT), claims that approximately 80 percent of the 200 largest printers in the U.S. own a Kodak Approval system.

The XP, KPG's newest version of this device, is available in two- and four-page sizes. Approval's laser dye-sublimation technology uses a tightly focused thermal laser beam. It heats the dye coating on a donor sheet until the dye sublimates (i.e., changes from a solid into a gas). The tiny spot of colored gas then leaves the donor sheet and clings to an intermediate receiver sheet. After all the spots for that particular color have been imaged, the spent donor sheet is replaced with a fresh sheet of another color, and the imaging process continues. When the receiver sheet carries all the spots required to complete the proof, it is ejected from the Approval. An operator then laminates the receiver to the final proof substrate on a separate lamination unit.

In addition to the typical cyan, magenta, yellow and black donor sheets, a variety of other donor sheets can be used in conjunction to simulate a wide variety of non-process spot colors. KPG received a 2000 GATF InterTech Award in recognition of its Recipe Color software, which calculates the exposure and positioning of multiple donor colors to provide matches on a wider range of spot colors than is possible with CMYK-only devices. According to Kodak, even metallic colors can be simulated successfully using this recipe system.

KPG also manufactures donor sheets for imaging proofs on a select number of thermal platesetters, including Creo's (Bedford, MA) Spectrum and Lotem devices. This material, known as Kodak Approval Digital Proofing Media/Type 2, is one of several products compatible with a process often called infrared (IR) thermal laminate proofing. In addition to the Approval Type 2 media, KPG offers Matchprint Laser Proof material recently acquired from Imation. This product was the first to be developed for use with thermal platesetters.

“The KPG material has been extremely consistent — we almost never have to recalibrate,” says Ron Barnett, electronic prepress manager at Hatcher Press. “We used to make proofs on a two-up Approval, but once the Spectrum came out, it allowed us to make a halftone proof the size of our press sheet from the same RIPed data that will eventually image the plate. We purchased two Trendsetters: One is dedicated to making plates while the Spectrum proofsetter makes proofs at least 70 percent of the time. This scenario allows us to use it for the occasional rush plate. It also functions as a back-up for our dedicated platesetter.”

Barnett is also looking forward to testing DuPont Imaging Technologies' (Wilmington, DE) Color Versatility (CV) donor sheets, which enable the creation of custom color donor sheets as part of its WaterProof thermal halftone-proofing-system product line.


Thermal imaging is also at the heart of Polaroid Graphic Imaging's (PGI) (Bedford, MA) halftone proofing system, featuring the PolaProof six-up imaging device (winner of a 1997 GATF InterTech Award), as well as the Prediction 2000, a fully automated two-up proofer.

Polaroid calls its technology Laser Ablation Transfer (LAT). Unlike laser dye-sublimation and IR thermal laminate proofing, LAT utilizes pigmented colors (rather than dyes) and transfers spots from the donor sheet directly to the substrate. PGI also offers a variety of different color sets; in addition to SWOP and GRACoL process colors, Eurocolour, Hexachrome and several spot colors (including metallic silver and gold) are also available. In the case of the PolaProof 2230, these donor sheets must be loaded and unloaded by hand — a process that takes some time and practice to perform consistently.

Despite its relatively labor-intensive nature, PolaProof's close resemblance to offset printing has made it a hit with many printers, including General Printing (Honolulu). “The PolaProof is the standard by which everything else is judged,” reports Ken Slavik, General Printing's CEO. “It's constantly repeatable, and through calibration we've been able to accurately match the proof to the press. Since it's labor-intensive, for large jobs we sometimes run Agfa Sherpa inkjet proofs on everything and do scatter proofs of just the images on the PolaProof — that strategy has allowed us to reduce our proofing costs by half.”

All of the companies interviewed for this article employed a similar strategy of utilizing a large-format inkjet proofing device, such as Agfa's (Ridgefield Park, NJ) Sherpa 2, in conjunction with more expensive, halftone-capable thermal proofing systems. It seems that even for printers who value their dots, it's useful to have a cheaper alternative for less-demanding proofing applications.


Fuji Photo Film U.S.A. Inc.'s (Hanover Park, IL) FinalProof debuted just in time to take first-place honors in Seybold's Digital Color Proofing Shoot-out 2000. Employing what Fuji calls thin-layer thermal transfer, FinalProof uses pigmented CMYK donor materials to image high-resolution proofs up to 21.5 × 32.25 inches. Like many other halftone-proofing methods, the FinalProof generates a flopped-image intermediate receiver sheet that must be laminated offline before the proofing process is complete.

The high-end thermal halftone imaging device, has made a believer out of Sally Wack, production manager at Irwin-Hodson Co. (Portland, OR). “The match between proof and printing press is the closest that we've seen,” says Wack. “Occasionally, when we have to run jobs from supplied Iris prints, the press operators become frustrated and really struggle to get a color match. They immediately ask that we re-output the job on the FinalProof.”

In addition to the color reproduction, Wack is impressed with the FinalProof's reliability: “It's fully automated, so if we're working on a project in the evening, we can send it to the FinalProof, and in the morning, all we're doing is laminating.”

Inkjet printers' combination of quality and affordability are making these devices a popular proofing option. Recent drop-on-demand advancements are enabling the development of halftone-dot-capable inkjet proofing systems.


BESTcolor's (Westchester, OH) ScreenProof, a software module for its BESTColor RIP, made its U.S. debut at Print 01, where it was shown imaging proofs at common screening frequencies.

Using the latest five-picoliter inkjet printers, such as the Epson (Long Beach, CA) Stylus Pro 10000, BEST claims accurate reproduction of up to 200-lpi halftones. ScreenProof differentiates itself from a handful of competing software programs by directly supporting color-measurement devices from X-Rite (Grandville, MI), GretagMacbeth (New Windsor, CT), ColorSavvy (Springboro, OH) and others. BEST installs and configures the ScreenProof application and printer through a network of resellers and integrators.

“So far, our typical customers for ScreenProof are larger print shops that like to have one of everything,” reports George Katter, digital service manager for Dot Doctors, a Chicago-based BEST integrator. “These companies may already have other forms of large-format halftone proofing devices. They are looking for something that approximates that level of quality but at a price-per-proof that is much less expensive. As a company's only proofing device, it's not for everybody — even with the fastest-available hardware, you're looking at 25 minutes of processing time for an eight-up proof.”

From low-cost inkjet devices to high-end digital proofs that exceed the cost of analog options, today's proofing market truly has something for everyone. With such an array of possibilities, there's really no reason not to put the same dots onto your proof that you'll burn onto your plate. Whether you are concerned about predicting pattern interference, minimizing press makeready time or are simply trying to placate that old-school buyer, an increasing number of printers believe that putting dots in your proof means never having to say you are sorry.

More vendor proofing news

  • GMG (Stuttgart, Germany) will show its proofing technology on a variety of printing devices at Ipex. Epson, basysprint, Fuji, Hewlett-Packard (HP) and Turning Point Technologies will feature GMG's ColorProof and DotProof. ColorProof calibrates inkjet proofing engines for producing digital contract proofs color-matched to the press. A new DotProof option reportedly enables the output of halftone contract proofs with original screen data on Epson and HP large-format inkjet printers. Blanchard Systems and Zenplex are the U.S. distributors (see

  • Polaroid Graphics Imaging (PGI) (Bedford, MA) has signed a dealer distribution agreement with xpedx (Covington, KY). Xpedx will distribute PGI's digital halftone proofing systems as well as all consumables for PGI's proofing and other systems.

  • PerfectProof's (Wilmington, DE) ProofMaster is a digital RIP that runs on both Mac and PC platforms. Users can employ either standard ICC profiles or “FingerPrints” to obtain consistent results. The RIP automatically calculates press parameters, such as ink transparency, dot gain and overprint. One computer equipped with the RIP can drive two printers simultaneously. The system enables on-screen enlargement/reduction, rotation, copy, cropping, tiling and nesting. ProofMaster supports Epson Stylus, HP, Canon, Mutoh, Roland and Novajet printers.

  • Screen's (Rolling Meadows, IL) SureProof inkjet proofing system uses a hot-folder workflow and runs on a Windows platform. Its integrated HQ-RIP core fully supports PostScript, PDF, TIFF and other file types. SureProof is supported by 11 Epson Stylus Pro and HP Design Jet printers, including the Epson 5000, 7000, 7500, 9000, 9500 and 10000, and the HP 1055CM, 2000CP, 2500CP and 5000.

  • RealTimeImage's (San Bruno, CA) RealTimeProof Partner enables third parties to plug RealTimeImage's image-streaming engine into any digital production and workflow system, including asset management and custom database programs.

The company also has teamed with Printable Technologies (Solana Beach, CA) to launch an online forum on soft- and remoteproofing technologies and industry applications. See the NewProof Forum at

Related articles online

See for these archived articles:

  • “Remote proofing: close at hand,” February 2002, p. 18. Read about the latest desktop devices, color copiers and printers, RIPs and file-transfer software.

  • “Remote proofing delivers,” September 2001, p. 36. An overview of remote- and soft-proofing options, including real-world examples.

  • “Platemaker and proofer: a two-in-one system,” August 2001, p. 54. Great Lakes Graphics (Skokie, IL) is a 60-employee, 65,000-sq.-ft. operation that specializes in packaging, brochures, annual reports and posters. The company makes plates and proofs on its ECRM (Tewksbury, MA) DesertCat 88.

  • “Digital proofing solution hits the spot,” March 2001, p. 48. Cohber Press Inc. (Rochester, NY), a $28 million, 155-employee firm, specializes in multicolor marketing material, catalogs, direct mail, equipment manuals and point-of-purchase material. The printer uses Kodak Polychrome Graphics' (Norwalk, CT) Recipe Color software to produce spot colors on its Kodak Approval XP/XP4 digital color proofing system.