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Sep 1, 1997 12:00 AM
Ask any printer to pick the number one item on his technology wish list, and the answer will have to do with proofing. There is no doubt that proofing is seen by many graphic arts execs as a stumbling block on the road to achieving digital workflows. And although everyone agrees that proofing is a problem, opinions vary over what area of proofing represents the biggest challenge. The argument rages on. Contone vs. halftone. Analog vs. digital. Production proof vs. contract proof.
Digital production techniques with new technologies have brought unique problems and solutions to proofing. The question still remains: Where are we, where are we going, and what's changed? Although we don't have all the answers, this report, co-sponsored by DuPont and The Pitman Co., will provide some insights into the critical issues surrounding the proofing cycle.
Today, we exist in a world that is both analog and digital. Proofing is no exception. So let's start by looking at some definitions to help put the challenges in better focus.
Analog proofing consists, of course, of proofs made from film. In this category, there are two types of proofs--overlay and laminate.
Now let's look at digital proofing, or proofs directly imaged by a device that uses digital data. In this category, again, there are two types. Digital halftone proofs create screens mimicking those produced on a press. Digital contone proofs use some form of dithered imaging technique to simulate the colors produced by a press.
Contone proofs can be created using different technologies, including dye sublimation (D2T2) or ink-jet. D2T2 uses a dye diffusion transfer process in conjunction with thermal resist heating elements. Ink-jet is a direct imaging process using pigments or dyes.
The above definitions are included in a new study commissioned by the Graphic Arts Marketing Information Service (GAMIS), a special interest group of Printing Industries of America (PIA). The study, which focuses on changes and new directions in the proofing arena, was conducted by Cloud Information Services.
In the professional graphic arts industry, proofing plays a role in a variety of steps from creation to completion of the finished product. As a result, no one proofing method is suitable for all functions. However, all proofs serve one very basic need--they are the basis for communication, both internally and externally. As a result, all proofs must be predictable, consistent and provide an accurate representation of the object that will image on press.
In addition to its primary communications-oriented use, a proof also can and should be used as a process control tool and, finally, as a verification of an agreement to produce. Proofs are used as a sort of an "insurance" plan, says industry consultant Dave Zwang. "If something goes wrong, the proof can be a basis for further negotiations."
Ken Cloud has identified five generic types of proofs as part of the GAMIS study:
* Design proofs--A hard copy or soft display of work-in-process. The final rendition is often a tight comprehensive of the designed product.
* Color proofs--These are produced from scanned images and used to verify color corrections and adjustments for the printing process. This category includes scatter proofs, randoms, etc.
* Page proofs--These are produced during the page assembly process and serve as a reader spread of the intended printed product with all elements in place. They are generated as internal production control tools, but also can be used as contract proofs.
* Contract proofs--Typically produced as the last step in the color/page assembly process as an agreement between the agency, client and color trade shop. This proof is for external communication.
* Production proofs--Frequently referred to as a blueline or Dylux, this is a proof of the imposition for the printer's use in verifying print production specifics. It incorporates color control bars, cut marks, tile and shingling, etc.
How these various proofs fit into the workflow is depicted in the accompanying diagrams. Current workflow shows functions that are mixed between analog and digital. The future workflow reflects a completely digital production operation.
As recently as five years ago, Color Electronic Prepress Systems (CEPS) were considered the method of choice for producing film. Their adoption was not limited to prepress shops; it was not uncommon to find these $1 million behemoths in operation at high-quality commercial printers. Noted for the "magic" they performed, they became the workhorse of color production until the early 1990s.
The introduction of PostScript, however, changed the picture dramatically. By 1995, the market for traditional CEPS dried up, replaced by lower-cost systems that accept TIFF images and output to imagesetters. As a result, the exclusive world of CEPS was replaced with systems that many more operations could afford.
The production of color pages, therefore, is no longer limited to a handful of companies. And this increase in digital color production sites is increasing the number of sites producing and proofing color pages, points out Cloud in the GAMIS study.
While the number of sites increases, the volume of work at each site remains constant, adds the consultant. Therefore, the volume of proofs generated at each site is commensurately stable. "This may seem counter intuitive to the increased use of color and shorter run lengths," points out Cloud, "but as the entry price for acolor production system drops from $1 million to $100,000, the number of pages necessary to justify the expense also drops significantly. The increase in the number of sites producing color, therefore, is growing far faster than the increase in the number of pages produced per site."
According to the GAMIS study, the decline is fueled by the change in demographics, not the reduction in pages produced by the existing sites. Overall, those sites that have been producing color will maintain at the same volume they always have. It is the new sites, however, producing color on a more casual basis, that bring the overall average down.
As a result of changing workflows and the democratization of the color production process, proofing expectations have changed.
Everyone knew what was expected during the analog age, based on years of experience. Everyone was involved in the process, having done this before. The proofs didn't need to be accurate so much as they needed to be consistent and, therefore, predictable. Individuals involved in the process didn't really understand what CMYK color was. They only knew how the process predicted a result on press.
With the democratization of color production, the process involves organizations unknown to each other. As a result, a method of determining color is vital. The new workflow requires definitions for each piece of the puzzle. This is what standards work encompasses.
The Specification for Web Offset Publications (SWOP) is an excellent example of how standards affect the process. SWOP was developed to control the color of advertisements across multiple publications. It specifies what inks to use on press and what dot gain to manage, making it possible to develop a standard way of proofing from film to calibrate the process. It also provides a common expectation of what "color" is being printed using CMYK inks.
Most printing, however, is not done to SWOP standards. This is not necessarily bad, claims Cloud, because most printing is done with cleaner yellows and more vibrant colors in general.
Color management systems are being developed to help move us closer to "plug and play" color across organizations. The premise behind color management is that it is not necessary to know and understand every step of the process. All you need to know is the step you are involved with, explains Cloud in the GAMIS report. "If each individual step is calibrated to a known point, then the process can adjust for changes downstream by the receiver, who adjusts from that known point to his or her process."
Since CMYK is not a known point (i.e., there is no colorimetric definition for CMYK as used by the printing industry), another reference point is used. Typically this is the CIE XYZ color space. Scanned images start as RGB data, are converted to CMYK and the CIE XYZ reference point for the CMYK data. This data then is color corrected and manipulated before being proofed by a device calibrated with its own CMYK to CIE XYZ space. Then data goes to press where the press' color calibration is applied. (See sidebar for more on CIE.)
The flaw, of course, is that there are three separate adjustments made for the raw data to CMYK extrapolation: one by the scanner, one by the proofing device and one by the press operator.
The advent of color management does not, in or of itself, solve the problem. As we combine the standardization of the process with color management systems, we get closer to a solution. This allows the concept of working with "calibrated CMYK" data, which is data with a known CIE XYZ value defined through standardization. This approach, while not perfect, will help reduce the differences by bringing the data closer to a common point.
The GAMIS report also emphasizes that color management and color calibration are two different processes, often confused. Color calibration--adjusting color for device idiosyncracies--does not change the resulting image. It only calibrates it to an output device.
Also involved in color management in the digital world is the increasing use of process control tools during printing. The industry has the ability to print "by the numbers." Printing itself is a more controllable process in which the press can be set to optimum performance characteristics and the color adjusted to achieve the desired results for the press' best operating condition.
This results in reduced demands on the color proof, contends Cloud. "The proof must be a consistent predictor of the final results, but it is not as critical as a press control tool. The proof, instead, is focused on verifying the integrity of the digital data, not as an end by itself in managing the process.
Carrying this principle to its logical conclusion is George Fiel at Image Systems in Menomonee Falls, WI. The firm operates digital presses and conventional sheet-feds with computer-generated plates. Clearly, proofing is extremely important in this digital environment, and Fiel's company has worked long and hard at implementing a calibrated "print by the numbers" process. Over time, it has been so successful that 50 percent of the work produced is done so without client press approvals. The client is confident that signing off on a proof will achieve the desired end result.
Image Systems enjoys a completely digital workflow--a goal not achieved as yet by most printers. Therefore, the question of analog versus digital proofing remains for the majority of the industry.
In fact, analog proofing has regained momentum during recent years. One of its roles is in proofing more than four colors. Products such as DuPont's WaterProof are not only two-sided and foldable, but recent introductions allow for spot coatings. WaterProof CV (color versatility), for example, adds the full spectrum of the Pantone Color Matching System using custom blendable inks.
It was only 20 years ago that DuPont introduced analog proofing with the launch of Cromalin. The industry reacted with skepticism--at best. In response, DuPont instituted a full-blown marketing campaign aimed at the design and advertising community. Once print buyers started to ask for Cromalin, its success was almost guaranteed.
The introduction of digital proofing has many similarities to Cromalin. This time, however, the move comes when our industry still is trying to define responsibilities for various operations and stages of production--a problem that didn't exist back in the 1970s.
There are those who argue a digital proof doesn't show any problems generated by a filmsetter or processor. However, experts point out that checking film may be a security blanket that has no functional value. In efficient operations, the imagesetting process is checked daily to verify that it is performing according to specs. As a security check, most operations include a step wedge and check the density of the film. Therefore, with a properly calibrated process, if the density of the values in the step wedge are correct, the color will be correct.
The GAMIS study also addresses the image quality issue, closely intertwined with the halftone/non-halftone argument. Ignoring the issue of dots for a moment, the various digital proofing alternatives currently available offer more than acceptable quality levels in terms of consistency, reliability and flexibility. Overall image quality is no longer a valid reason to discount digital proofing.
"The real issue in acceptance of a proofing technology has more to do with the market's willingness to learn how to evaluate a proof (relative to the final printed piece) than it does to the technological limitations," says consultant Zwang.
Interestingly, one of the findings of the GAMIS study pointed out that although digital can replace analog off-press proofing, it still cannot replace press proofing. Press proofing is alive and well in North America, claims the study, generating multiple "proofs" for distribution of multiple copies to multiple locations.
Neither analog nor digital proofing has displaced press proofing in this environment largely because of the costs, claims the study. Cloud finds that an analog proof may be priced at $50 to $75. If we assume that 10 publications want 25 proofs each, this would cost $550 for 250 press sheets. Compare that to $875 for 25 ink-jet proofs at $35 per proof or $1,600 for 25 laminate proofs at $64 each. Digital proofing, while costing less than analog, still doesn't approach the cost of press proofing in these applications.
The exception to this is the use of an electrophotographic digital press to generate proofs. Although it is unlikely that a firm would purchase such a device solely for proofing purposes, the incremental cost per copy to run a digital proof on a digital press is extremely low. There are some organizations in the industry that have discovered a lucrative market for producing "samples" on digital presses--simply another term for multiple proofs.
Which leads us to a discussion of halftone versus contone proofing approaches. This is an argument that has raged since the dawn of digital proofing. And, in fact, there is no right or wrong answer. In today's workflows, it is probable that organizations will require both types of proofing solutions.
True halftone proofing does have its benefits. For example, the only way to predict moire patterns is with a halftone proof, which is an accurate rendition of the dots to be used in the final printed piece.
The second printing artifact from halftone dots has to do with high-resolution image blending. This process is used to blend areas in which two halftone images interact or a halftone image and linework interact to smooth the transition between the two. The most common application is in the creation of traps. A halftone proof provides the tools to verify that this function has been done and done properly.
On the other hand, notes Cloud, techniques have been developed in contone proofing to verify whether objects have been trapped. However, when sophisticated trapping is being done, only a halftone proof will show the effect of the different traps used.
A number of printers and trade shops have adopted contone proofs for contract purposes--usually because of their availability and low cost. However, there is a caveat for why contone proofing is acceptable.
"For half of our customers, a dye-sub proof is acceptable as the contract proof," explains Jack Ryan of Tri Tech, a 50-employee prep house in Pennsauken, NJ. "These are customers using stock photography or reproducing previous jobs so they have a general idea of what the final printed piece looks like."
A halftone proof has its highest value as a final proof. According to the GAMIS study, if halftone proofing can provide the same dot as used on press and do it cost effectively, about one-third of the market will demand this approach. However, whenever a halftone proof is used, a contone proof also will be used for various iterations in the process leading to the final contract version.
An added benefit of digital proofing is its ability to reduce cycle time. Because of its ability to eliminate the 12-hour "black hole" of overnight carriers, remote proofing is starting to be a welcome option for "rush" jobs. Remote proofing allows prepress operations to send proofs to clients using phone lines.
ISDN and other telecommunication technologies growth, coupled with developments in file compression technology, are speeding the adoption of this proofing approach.
There are problems, however. Consultant Zwang points out that the dilemma of how to ensure that what clients view matches what press operators see in the printing plant still remains.
Developments in color management systems that support Apple's ColorSync (a standardized system-level color management technology for the Mac), likely will lead to a resolution of this problem. ColorSync provides the ability to "profile" proofing devices to establish their individual characteristics and compensate for variances. This allows users to communicate a file to different proofing devices with some degree of assurance that the output can be used to judge the acceptability of the final printed piece. "Of course, a certain level of interpretation still will be required,"cautions Zwang.
There are a number of solutions now on the market addressing remote proofing. For example, 4-Sight ISDN software and DuPont Digital Waterproof or PreView proofers, can maintain color calibrations across networks. The DuPont proofers use CIELAB-based color management technology to achieve consistency between prepress operations and their customers.
The remote proofing system is most likely to supplement final contract proofing. "What the customer needs is to see a reasonably accurate color comp very quickly," contends John Welch, president and CEO of Jackson, MS-based K&W Inc. "We believe that a 150-dpi file is going to give enough resolution to achieve this goal."
Some proofing devices are becoming more calibrated and controlled. These units feature tools such as on-board colorimeters and automatic calibration software that allow clients to easily keep their units calibrated.
At Print 97, DuPont is introducing its ColorNet technology, available with Digital WaterProof and PreView digital proofers. The CIELAB-based system makes achieving accurate proofer calibrations easier, without trial and error. It also controls color to tight tolerances over networks and in remote proofing applications.
Another driving force for remote proofing is the consolidation of the industry, maintains Cloud. "With the big gobbling up the little, more and more distributed printing is emerging. In this scenario, prepress work is performed at one location and films shipped to another location for printing. A few printers are using remote proofing rather than courier service to facilitate these types of workflow."
If the goal is quicker and lower cost proofing, why isn't "soft" proofing the norm? In the past, the color of a monitor has not provided a good match for the printed page. Most monitors lack consistency and aren't a good tool for checking element position--they don't provide the detail required unless the image is blown up so far the operator loses page perspective. In addition, monitors are not very mobile.
Recently, however, new developments have perhaps lifted some of the barriers to soft proofing. During 1996 the Graphic Arts Technical Foundation (GATF) and R.R. Donnelley announced the development of a flat panel display using a pigmented acrylic color foil. These color foils, explains Cloud, are designed to provide a colorimetric match between the monitor and the printed page.
In spite of these developments, soft proofing likely will not replace hard copy proofing. It may, however, reduce the number of errors that get through, thereby reducing the number of iterations required in the process.
Computer-to-plate (CTP) workflow also is driving some forms of soft proofing. At present, many of these workflows use a soft proofing step. After imposition, the file is checked on the monitor to verify that all register marks, color bars, folios, etc., are in their proper place and in registration. Cloud reports that this soft-proofing step represents a 10 to 20-minute process per set of plates. Once the job is checked, an imposition proof is made, a 30 to 40-minute process for an eight-up format.
"This soft proofing step is invaluable as a safeguard against plate errors," says Cloud. "Seeing the critical elements blown up on the monitor provides more detail than looking at a 300-dpi ink-jet proof. It also is faster than waiting for the hard copy proof to plot."
However, imposition proofing is emerging, driven by the advent of computer-to-plate. As more imposition proofs are available, the soft proof step will become redundant.
Although we think of proofing primarily in terms of color checking, there are other issues that need to be addressed to enable digital workflows. Press and bindery requirements traditionally have called for "two-sided" proofs to check back-to-front page alignment. This is where the imposition proof finds its most loyal adherents, linked directly to the growth of CTP.
Currently, there are a variety of solutions on the market addressing imposition proofing. Unfortunately, most are not two-sided, an attribute that printers find vital as they wish to use these proofs both internally and, in some cases, externally to communicate with clients. Double-sided proofing, of course, can be folded, allowing operations to create "finished" products for review and reference.
During the Vue/Point Conference held in March of this year, a number of panelists were heard to strongly request "a low-cost, double-sided imposition proof similar to the Dylux used in traditional applications." During Print this month, DuPont, in conjunction with Gerber, has responded to this request with the introduction of Digital Dylux, a "digital blueline" for computer-to-plate impositionproofing.
Optimized to run on Gerber's Impress double-sided signature proofer, the Digital Dylux proofing media is designed to accept two-sided ink-jet application. Gerber's registration system reportedly keeps the pre-punched paper in tight register from front to back.
The Digital Dylux materials and Impress signature proofer are optimized for monochrome proofs at 600 dpi or full color at 300 dpi. The proofs will fill printers' needs for checking layout and content of files before outputting final film or directing files to a platesetter. This new approach is seen as a complement to existing contract digital proofs used for color approval.
As this example proves, today's proofing problems are being addressed by technological developments. The ultimate goal, of course, is to reduce print production costs and cycle time. But new product introductions also will give users a renewed level of confidence--what you see in the proof is, indeed, what you get off the press.
For more information, please refer to the charts on pages 27 and 30 of the September 1997 American Printer.
In 1931, the CIE (Commission Internationale De L'Eclairage) established standards for a series of color spaces that represent the visible spectrum. Using these systems, it is possible to compare the varying color spaces of different devices against repeatable standards.
CIE color systems are device independent--meaning the range of colors that can be found in these color spaces isn't limited to the rendering capabilities of a particular device or the visual skills of a specific observer.
The goal of the CIE was to develop a repeatable system of color communication standards. The standard observer and XYZ color space were the foundation of this framework, however, the unbalanced nature of the XYZ space made these standards difficult to address.
In 1976, therefore, CIE adopted L*A*B* (CIELAB) as standard. L*A*B* refers to the three main attributes of color--hue, lumina (lightness) and chroma.
L* refers to hue, which is the way in which we perceive an object's color. A* refers to its luminous intensity--light to dark. B* refers to a color's chroma or the vividness or dullness of a color. In other words, chroma indicates how close the color is to either grey or the pure hue.
The International Color Consortium was developed to standardize color on the desktop. The consortium developed the ICC profile, which describes color in the CIE XYZ color space. This profile format can operate on any computer operating system on any platform to handle colortranslation.
The standardization of color space is an important part of color management. Color gamut is another important component in the mix. The gamut of any device is the portion of the CIE XYZ model it can reproduce. For example, monitors display colors that cannot be reproduced on press due to the fact that the CMYK color space has a much smaller gamut than the RGB color space used by monitors. Scanners, proofers, monitors and presses all have their unique part of the CIE XYZ color space that they can reproduce.
The goal of color management systems is to solve three problems in the production process--characterization, transformation and calibration. Characterization is the measurement of what color gamut a device (such as a scanner, monitor or press) can produce. Transformation is the ability to translate from one color space to another. Calibration is the process of correcting for changes in color as conditions change or the device shifts over time.