CTP Chapter 5

Chapter 5 ― CTP & Digital Proofing

Traditional proofing on an offset proofing press is still widely used by large advertising agencies that need to distribute proofs to a large number of reviewers and approvers, however, traditional off-press proofing, made by exposing proofing media via films has been totally replaced by digital forms of proofing in the CTP workflow. Even a “proofing press” today may be an Indigo, Xeikon, Xerox, IBM, or other digital printing system. Furthermore, designers and layout artists are increasingly making use of desktop scanners and color printers and often refer to color prints as “proofs.” So what is a proof in the CTP workflow? The GCA CtP Users Group reviewed the various roles of color prints and proofs and provides the following break down:

Digital Workflow Function	Proofing Category	Description*
Creative/Publish	Concept**	The creative function is one that turns a concept into a design. The proof is a means of the artist to communicate the ides.
	Content**	The determination of what text and elements are to be published. The proof is used to verify the accuracy of the text and elements. Content is also checked in the contract proof.
Prepress		The process of converting the concept and content into an un-imposed final digital document to be used in the plate making process.
	Work in Process**	Intermediate proofs that are used to evaluate color and image content, which may or may not include text. Also, this proof may be used to position elements within the page.
	Contract	A proof, often called a final proof, contract proof or production proof, to distinguish it form a pre-proof, “proves” what the digital representation of an image will produce on press. A hard copy image, it shows the customer what the production press is expected to produce from the in put digital information. Once Accepted, the proof becomes a customer-approved guide for the pressroom. Regardless of the technology used to produce it, to be accepted as a proof, it must meet industry requirements. The “contract proof” definition is quoted from the GCA IPDC committee. In general, this group is dealing with publications and used SWOP as a standard. For other printing, different standards of printing conditions would apply. The requirements of a proof may differ, dependent upon the application.
Preflight	Verification	Prior to electronic imposition, a final verification of file integrity, completeness, and accuracy needs to take place. This may take place in two checks.
	Software	There are many “preflight” software applications that may be used to verify several aspects of file integrity.
	Hard Proof	A hard proof may be made at this point. If the same RIP technology is used here as that which is used to image the plates, this proof will predict any changes from the contract proof. For systems that support a “RIP once, output many” (ROOM) workflow through the use of raster based intermediate file formats, the raster data used for making the hard proof will be used for making the plates.
Electronic Imposition	Imposition Check	Prior to imaging plates, a check assuring the correct imposition, pagination, marks, etc. is made. At this final stage, a digital proof may be made and can be gathered in imposition book format.

* Some of the definitions used above have been taken from the GCA Industry Policy and Direction Committee’s The Business of Digital Production.

** These proofs are “preproofs,” meaning that they are made prior to the authorized “contract proof.”

The Various Functions of Proofs. Each category of proof, as described above has different functions in the workflow.

Concept: The purpose of the concept proof is to convey the idea in the form of a design. It is used as a developmental tool. In addition to the conveyance of the idea, this proof will be used to verify element and text position, fonts to be used, color breaks to by applied, and any other deign related items.

Content: This proof is used to verify the accuracy of the text and elements to be used in the design of a given page. In addition to checking the actual content, detail checks for grammar and spelling should occur.

Work in Process Proof: The reproduction of digital art, scans, and digital photography often requires manipulation, in addition to the initial capture and creation, in order to be consistent with the customer’s expectations. These expectations can be as straightforward as blue sky and green grass or as complex as matching the hue of thread provided to the printer and found in plaids in a picture of a garment.

Contract Proof: After individual image elements have been corrected to meet customer expectations, these elements are combined with text, and a page is produced. At this stage, mechanical tints and effects are also added. A full-page color proof is used to evaluate the “correctness” of the page. When viewed in page format, we answer the following: Do the image elements meet the customer’s expectations? Are all of the elements/text positioned correctly and at the right size? Is the trapping correct? Once this proof has been approved by the customer, it is designated a “contract proof,” and used as guidance for the pressroom. In some applications, there will be two “contract” proofs: one for hue and separation qualities and one for mechanical accuracy.

Preflight: Software can be used to identify any missing linked elements such as scans and fonts. They also verify that a postscript file is not corrupt. These programs are becoming more sophisticated and are starting to also optimize various aspects of files, including page geometry.

Page Proofs: At this time page proofs may be used to verify that you have a correct file: type has not re-flowed or been substituted. All images are high resolution. If possible, the RIP used to create this proof will be the same as that which will be used to image the plate. This provides the opportunity to identify any potential changes from the contract proof caused by a different RIP interpretation. This is a mechanical Check and not intended to verify hue. For systems that support a “RIP once, output many” (ROOM) workflow through the use of raster-based intermediate file formats, the same raster data used for making the hard proof will be used for making the plates. This step may therefore not be required.

Imposition/Pagination: Imposition is the function of positioning the pages on a printing plate. At this step color bars, fold marks, and other press required images are also positioned to be imaged on the plate. At this point in the process all individual elements of a page, and then each individual page, has already been approved. Preflighting has occurred to assure the process has not caused any changes to occur from the approved contract proof. Therefore, the only verification or proofing that needs to occur is to assure the accuracy of the imposition and pagination. Here we verify that we have the correct pages in correct position, the correct color bar and pressmarks.

Types of Proofing Technologies. There are many types of proofing technologies available today. General categories include:

Each of these proofs can play an effective part in a digital workflow. It is important to recognize that meeting a customer’s expectation is the objective. These expectations vary widely and there fore, no one proofing solution is right for everyone, in any or all of the functions of a digital workflow. Work in process and contract proofs include ink jet, halftone thermal laser, thermal pigment sublimation, dye sublimation, and photographic types of proofing systems. These proofs are used in a similar fashion as the traditional analog proof; both for work in process and as a final contract proof. Vendors offering contract proofing products include Kodak Polychrome Graphics, Fuji Photo Film, Optronics, Polaroid, Screen, Presstek, and CreoScitex.

One recent technology introduction is “Drop on Demand” (DOD) ink jet. In DOD a piezoelectric transducer is used to form a bubble of ink, rather than mechanical methods, which allows ink jet manufacturers to make smaller bubbles of ink. With smaller ink bubbles, ink jets can now reach much higher resolutions than just a couple of years ago. The introduction of DOD ink jet devices to the market has reduced the price point of proofers in the last couple of years.

Most intermediate proofing devices use dye sublimation. Dye sublimation is well established and is being used for remote proofing as well. Laser pigment transfer is offers slightly better quality, but at a greater cost. Continuous ink jet is also used in high-end work as an intermediate or even a contract proof.

Overall, the selection of proofers and proofing technologies continues to grow. Furthermore, the cost of proofing is dropping, the quality is improving, output performance is improving, and consistency is improving. There is a need for more mature proofing standards for digital color and exchange.

Proofing Issues and Variables. There are many issues currently being discussed by virtually everyone throughout the graphic arts industry related to digital proofing. The CtP Users’ Group believes one could summarize all of them in one question: “Will the customer’s expectations be met based upon a contract digital proof match to the end printed product?” For the printer to answer this question, the printer must understand and study the variables of digital proofing:

Hue Match: Among various proofing technologies, and even within a technology type, different vendors’ devices have the ability to produce different color gamut reproductions. Some portion of the color gamut they are capable of reproduction, are not reproducible with ink-on-paper printing. It should be mentioned that this limitation is also true with analog proofing technologies.

Dots vs. No Dots: Most digital proofing technologies today do not provide discrete halftone dots, therefore there are not any halftone dots in the proof. The obvious disadvantage to not having a halftone dot is that the proof will not predict artifacting, such as a screening moiré. The trade-off is cost. Additionally, for the proof to be an accurate predictor of artifacts, it should use the same resolution, screen angels, and dot shapes as the plate being imaged.

ICC Profiles/Color Management: Color management tools are beginning to become a significant contributor to the ability to have color matching across various output devices. Color management is in its infancy and is just starting to be used.

File Formats/RIP’ing Technology: Users of PostScript workflows still experience the occasional “unexplained error.” Some of these instances occur due to improper or complex nested files, while other errors occur due to improper handling of fonts, graphics, and logical page elements. In other instances, the RIPs that interpreted the PostScript data for proofing and plate making were different RIPs, which interpreted the PostScript differently. Naturally, a ROOM workflow, made possible by intermediate (raster) file formats will provide the most accurate reproduction for digital data. This is in contrast to a “single RIP” environment where, even though the same vendor’s RIPs are being used, redundant processing is required as the PostScript must be reprocessed for each output device. During these repeated interpretations, there is always the possibility for the operator, parameter, or machine errors. The use of PDF/X1 and TIFF/IT standard file formats is recommended and as these files gain acceptance, there will be changes in digital workflow procedures, especially as related to digital proofing.

Standards: There are many printing processes (i.e., offset web, sheetfed, gravure, etc.) and each process has many variables such as ink, age of equipment, paper use, and so forth. In order for a proof to be able to predict the final outcome, it must be based upon a clearly defined set of parameters, which it is attempting to emulate. With the number of potential variables in our process, a standard (i.e., SNAP, GRACoL, SWOP or FIRST) is necessary to allow the proofing manufacturer a defined target to match. With digital workflows, having standards is critical to assure consistency. Standard color characterization data for SWOP printing is provided in CGATS Technical Report 001 (TR001). Work is in progress to arrive at standard color characterizations for SNAP and GRACoL types of printing.

User Experience. One northeastern printer (United Litho) tried to fingerprint each press they were printing with, but found that this approach slowed production down. The now print to specified densities that are derived from their proofing device, which is the “house standard.” All other proofing devices that they use are calibrated to the one house standard proofing device as well. This allows them to, “keep all of the work moving towards the door.” They also use two different tone curves on their proofs: one for text-weight papers and one for cover-weight papers.

Their proofing device can use any production stock, but the economics of pulling, cutting, and handling samples of all customer stocks is not economically feasible. The company settled on a coated and an uncoated sheet as their house proofing stock. However, a couple of years ago, when SD Warren introduced the very white Strobe and all the designers started looking for ultra-white sheets, they found that they had to introduce another proofing stock that is extra white. Before they introduced the extra white proofing sheet, United had to add yellow to all of the colors so that what the customer was approving would match the press image on the whiter stock. Adding the second proofing stock solved this problem for United Litho. The United CSR indicate when the job should proof coated or uncoated and white or extra white — four simple choices.

As for moiré, United Litho has never pulled a job due to moiré; hence, they’ve never encountered a job that would show a moiré on one output device, but would not show on a second device. As for subject moiré, the resolution of the source scan and output must be sufficient to eliminate moiré in trouble images such as fabrics or blinds. The two-times-LPI rule of thumb doesn’t apply. Some images may need 8 or 10 times LPI resolution to image successfully. Another way to eliminate subject moiré is to employee stochastic screening.

One west coast publisher (Guest Informant) decided to move to a CTP workflow, but decided to in-house with prepress, and they had decided to use dye sublimation proofing devices to produce contract proofs. The publisher found that the more corrections that he made to the color compensation curve, the harder the device was to control. Imation came out and did color analysis for the publisher’s application in order to create a custom color profile. The custom color proofing service proved to be very worthwhile and effective.

A northeastern publisher (Taunton Press) decided that the economics were right to bring their prepress operations in-house in 1986. In 1990 they bought their first digital proofer. Some of the issues, such as a lack of a dot, they did not think were critical to the purpose of the proof, which is to communicate with their printers. However, their primary output was still film and they had to put together a tight film inspection program and questionable films were still proofed, but selectively. They keep a master proof in safe conditions that was used for quick comparison to the two proofing devices that they were using. They later added Color Zone color management software and a Gretag spectrophotometer to their operations. The use of color management and measurement allowed them to reduce variability to less than 4 delta E.

CTP equipment gives the printer an ability to hold highlight dots in the one and two percent range that could not be held a few years ago. One separator that uses the Imation Rainbow who created Rainbow proofs that ware approved by the client. The file included one and two- percent tints that the CTP device was able to replicate and which showed up on press sheets, but which were not shown on the proof!

Another printer (Daniels Printing) installed a Barco Impress imposition proofing device before implementing CTP in order to familiarize their operators with imposition, and in order to build customer acceptance.

Kevin Klein of Perry Judds, a $350 million printer, said that they ventured into digital printing as part of their CTP implementation plan. Kevin’s job was to find a digital proofing device to use in their CTP workflow, and his objectives were:

1. Colorants that match a standard. SWOP aim points were not sufficient for Kevin’s needs.

2. Flexibility in substrates available. Perry does a variety of work on different stocks and they needed a proofer that could be used with various stocks.

3. Control over density and dot gain. They need compensate of individual press characteristics.

4. A compatible RIP. A RIP that was consistent with their other output devices, such as the CTP imagesetter.

Perry Judd’s created a benchmark test. They collected press sheets with various objective and subjective images as well as the files used to create them and tested various devices in order to select a proofing device and RIP. However, this was only half the battle. The other half of the battle is dealing with digital proofs that customers provide. There is no way to control customer proofing, except perhaps with a standard test based upon color characterization data such as CGTAS TR001.

One of their customers, JC Penny’s, got all of their suppliers to use consistent measurement methods and agree to use the GCA L*a*b*-Ref certified reference to ensure their spectrophotometers were in agreement. Kevin said that now all of the JC Penny’s printers match one another very well, and they match TR001 as well.

One printer, Graphics Express, has Rainbows, Matchprint, Agfa Proof, Polaproof, Cannon’s, etc., “you name it we have it!” Not only do they supply there digital printing division with proofs, but they also provide proofs to commercial printers, magazine printers, catalogers and others, and they do not want to have “31 flavors” of proof profiles to use. Graphics Express produces SWOP proofs and uses the CGATS TR001 color characterization aim points and tolerances.

Few of the proofs on the market are really SWOP proofs; they are often either too warm or too cold. Users of SWOP proofing should verify that their proofing device is capable of producing SWOP proofs by visiting http://www.swop.org to review the list of certified SWOP proofing devices.

GAMIS Digital Proofing Study. Ken Cloud of Cloud Information Systems conducted a study of digital proofing for GAMIS. The study describes a future workflow that includes changes in how proofs are used. Ken said that 60% of page and contract proofing will be produced for internal of the customer uses and only 40% will be produced for external use (e.g., sent to the printer). The use of soft proofing will increase across the board. Furthermore, only 70% of digital imposition proofs will be produced for internal consumption and 30% for external use (e.g., sent to the customer!). Some of the general trends that Ken found include:

· Color management, standardization, and process control will improve digital production reliability

· Users will increasingly use extended color sets and special colors in addition to four-color

· The art and craft of the graphic arts will increasingly merge with the technology of graphic arts.

· Digital proofing, especially halftone proofing, represents the growth opportunity.

· Imposition proofing is a major new proofing category with a fast growth rate tracking CTP growth.

· Office technologies, especially ink jet, will be adapted to graphic arts applications and gain significant market share.

· Soft proofing quality will improve, but it will not be replace hardcopy proofing.

· Remote proofing will also grow, but again, it is an additional proof that will not replace traditional contract proofs.

· CTP workflows will drive the development of imposition proofing devices for internal production control and as a final proof for some applications.

The full study, with detailed analysis and the complete set of projections and numbers is only available to GAMIS members. For more information on GAMIS, please contact Jackie Bland at (703)519-8179. For more information on digital proofing studies and user specifications, visit http://www.digitaladlab.com and http://www.ddap.org.