We live in a fast-paced, increasingly technological world. Each day a new trend or technology can take us in a new direction or streamline an existing process. This is true in today's electronic publishing world where Digital Proofing technology holds the promise of faster turnaround and decreased costs versus conventional proofing technology. While digital proofs are not brand new, many of GPO's customers still struggle with the dilemma: When is the best time to use a digital proof? This question leads to a very important answer. After all, color is paramount to all of us involved in the printing process. While no proof can match a printed sheet exactly, there is a difference between the abilities of digital and conventional proofs to reproduce color. When using digital proofs, a different realm of variables comes into play as with any new process. Variables that were quite simply non-existent in the conventional-only days. While many of the variables are controllable once identified, there is one major concern when selecting between a digital and conventional proof. In this article we will identify that concern, examine what each type of conventional proof can and cannot do, and compare the two categories of digital proof.

Conventional Can-Do's!

All printing professionals know of the days gone by when all proofing was conventional. Films are made from camera copy or an imagesetter. Then those films are stripped-in and the flats are ready to proof. What type of proof would you use at this point? Let's refresh our memories with this list:

Blueline (Dylux) - Ultraviolet (UV) light is exposed through the film onto the proofing substrate, in this case paper. The paper's UV sensitive coating darkens and reveals the image area of the piece you are attempting to proof. This proof is best suited for text pieces or to check for overall registration and is also the least expensive.

Powder - UV light through the printing film exposes a backing sheet. The backing sheet becomes tacky after exposure and then a colored powder is sprinkled across the sheet sticking to the tacky areas. Once the excess powder is removed, you have an image that appears similar to the final printed page. This proof, though not used much today, is best suited to check a spot color break or a single color image. Please note that the color on this proof is not an accurate representation of the printed sheet because of the use of powder rather than an ink colorant. Since this method is being phased out of industry, cost will vary.

Overlay (Colorkey) - Translucent sheets of Cyan, Magenta, and Black are exposed with UV light through the printing films. The proof sheets are then run through developer and tacked up on a single backing sheet in register. This proof is best used to see the breaks of a full color piece and the color is comparable to that of a press sheet. Costs of an overlay proof are significantly more than a blueline, but less than a full-color laminated proof.

Laminated (Matchprint) - Sheets of CMYK material are laminated onto a backing sheet, then exposed with UV light through the printing films. After each color is exposed, the composite colored film and backing sheet are run through developer that washes out non-exposed areas of the C, M, Y, or K film. Then the next layer of colored film is laminated on top of the previous one. Once all four colors have been exposed and developed, you are left with a process color image that is a near match of the final printed piece. This proof is suitable for contract color match and overall register. This proof is the most expensive overall, but provides the best results.

These conventional proofing technologies made life easy. Normally, the customer would get a blueline and a laminated proof with every full-color job. The blueline shows all the text and registration on the job in a single color format, and the laminated proof gives the color as it appears on film. The press operator then matches, as best as possible, the laminated proof's color and can also use the same proof to check the design elements, trim size, and image position. This proofing process has become very reliable and the variables involved have been identified and controlled over time. So why migrate the industry towards an all digital proofing format?

Digital Dilemma

Digital proofing technology has one major conceptual advantage: streamlining of the process. The removal of printing films in the proofing process by going digital has many advantages. Material costs, labor costs, equipment costs, and time can all be reduced as digital proofs are perfected. Instead of outputting film from your electronic publishing environment, you can skip all that time and material and go directly to a proof. In this fashion, if an error is a found or changes are to be made, the printing films and costs involved with a re-output are not an issue. Changes can be made, a new proof can be output, and an "OK to Print" can be given before the final output to film begins. No more bins of scrap film due to changes or errors! No more long delays as a re-output is completed! Just a click here and there and a new round of proofs are off to the customer. When the digital process works as planned, large amounts of time and capital are saved.

Now you may be wondering why there is any doubt that a digital proof would be superior to a conventional proof, right? Well the doubt lies in the dots, always in the dots!

Dot Technology

In printing, dots are the foundation of how a piece looks. Every image on a printed piece is composed of dots, with the exception of line art and most text. How those dots are formed directly relates to how that piece looks. With that in mind, let me explain the issues that arise between conventional and digital proofs. All conventional proofs have the image on them formed by the dots present on the printing films, the same films that will make the plates that run on press. Therefore, the dots on your conventional proofs are most like the dots on the final printed piece. Now consider the digital proof. The dots are created by the proofing device without the use of the printing films. What does this mean? It means that the proof may not be reproducible on press! So how can you reliably use a digital proof as a contractually acceptable model of the final piece? Know what type of digital proof you are using.

There are two main categories of digital proofers that I will discuss: Continuous Tone (sometimes called a Simulated Halftone Dot Proof) and halftone dot proofers. Continuous tone proofers are the types that must be avoided as a final or contract type proof. The dots are produced in a non-standard pattern that does not resemble the "rosette" pattern that a printing press produces. The result is that you may achieve a color or effect that is simply not reproducible on film, plate, and press. The most vivid example of continuous tone technology is an inkjet proofer/printer. If you have used an inkjet printer at home or in the office, you may know what I am talking about. The print you make from the inkjet device may look good, but it doesn't come very close to the original. If you look closely at the image you produce on the page, you will notice that the dot pattern is fairly randomized and does not produce a crisp, high-resolution image. While newer, more costly printers are coming closer to a photographic quality, it is simply not as sharp. More importantly, that dot pattern is not what the final production pieces will look like off a printing press. If you look at any printed image you will see the "rosette" pattern I mentioned. The process color ink dots from a press are at specific angles from each other and therefore form a repetitious circular style effect that printers call the rosette pattern. GPO recommends only accepting a continuous tone proof for image placement or text reviewing purposes. GPO contracts may specify that continuous tone proofs are not an acceptable standard for color matching purposes. Consult your specific contracts for that information or call your Customer Service Representative.

Halftone dot digital proofs are the type of digital proof that can be accepted for color match and contractual approval purposes. The dot patterns put out by these machines are very similar, if not equal to the dot that will appear on press. While the dots are not created off the printing films, they are created in the same way that the films or plates would be. A laser creates the dots in the rosette pattern, just as a similar laser will do so for the films or plates. This method therefore increases the likelihood that the proof will be able to be matched on press within the range that a conventional proof could be. Consult your specific contracts for information on what specific brands qualify as halftone dot proofs or call your Customer Service Representative.

The halftone dot pattern.

That's A Wrap!

No proof currently does a better job at contractual matching than a conventional, full color, laminated proof. Creating a proof from the physical dots that will create the final product is the ultimate proofing solution. Yet digital technology is on the rise every day and getting closer to being as good as, if not better, than a laminated proof. Today's devices are good enough that the time and cost savings of the digital proof can outweigh the need for a conventional laminated proof. This exact premise is what keeps the technology rolling along. Just keep in mind what type of digital proof you are seeing for your job to make sure the image can be faithfully reproduced.

Hopefully the next project you have with GPO, you can use the information from this article to make the call as to what proof you can contractually use. GPO strongly recommends that for every job our customers supply on disk be proofed either conventionally or digitally. If you have any questions concerning digital proofs and your print project, contact your Customer Service Representative or the ePub section at (202) 512-1491.