Spring 2005                    return to newsletter contents page

CTP Workflow Creates Opportunity, Challenges

The end of film workflow means quality measurement tools have to change with it

by Alex Hamilton

Reprinted with permission of Converting Magazine, February 2005, Reed Business Information, a div. of Reed Elsevier, Inc.

In an all-digital CTP workflow, proofing systems are unable to render the press inking sequence without prepress system guidance. For example, an inkjet proofer won't overprint black text onto the opaque gold, which could needlessly delay production, even though that's what will happen on press.

Images courtesy of Esko-Graphics.

Yes, it's a tired old saw, but it persists because there's some relevancy to it, particularly for packaging firms that switch their operations from a film-based workflow to one using computer-to-plate imaging.

To be sure, the tasks haven't changed one bit: matching the design file to the structural/CAD file containing the die lines, dealing with multiple spot colors, trapping, compensating for dot gain, proofing.

Yet film is the ultimate quality-control tool. It provides a nice break in the process that lets the prepress service provider and the package printer synchronize their workflows and iron out any problems before the expensive and time-consuming step of making plates and mounting them on the press.

For example, who really cares about the ink order until it's plating time? A packaging designer working in Adobe Illustrator probably doesn't stay up at night worrying

about overprinting black text onto an opaque gold metallic ink. Yet it's the kind of thing that can wreak havoc in the pressroom and erase whatever meager profits a job might deliver to the converting firm's bottom line.

Working backward

Given that the press is where the action is, it's best to start your workflow assessment there and work backward to the designer, figuring out how smearing ink on polyester and paper by-products is going to change with a CTP workflow.

Dot gain is the attribute most significantly affected by CTP. Digitally imaged plates will hold both highlight and shadow details that simply would be lost in a film-based workflow, which means you've got to adjust the compensation curves, along with other parts of the workflow.

Jan De Roeck, Esko-Graphics worldwide marketing director for packaging software, notes that many measurement tools aren't capable of reading in 1 percent increments but, rather, offer 5- or 10-percent increments. Yet now you are going to be able to hold highlights in the 1-5 percent range, along with shadows measuring between 92-99 percent. Thus you've got to have the tools to measure exactly what's coming off each of your presses and to carefully document the results with each press/ink/substrate combination.

That measurement system must also be capable of discerning between opaque and transparent inks, De Roeck insists, which is one major quality parameter for color management and dot gain.

The ability to maintain details in both highlights and shadows goes all the way back to image capture and retouching. Although it would be desirable to use the same scan/image for offset, flexo, letterpress and gravure application (it sounds great?) the requirements of flexo, in particular, make the concept of a digital master, separated using different output curve, untenable. Artwork Systems' Michael Rottenborn advocates keeping the two separate and distinct.

In particular, the highlight details must be manipulated differently for flexo CTP, notes De Roeck, and that requires the retoucher to remove the "scum" dots prior to output, as they otherwise would mar the printed result.

Managing Color

 Color management based on the ICC model is slowly migrating from commercial printing into the world of packaging. Yet this is likely to be a challenging ride with "shelfware," as packaging printers rely almost exclusively on spot colors and specialty ink/color systems to achieve their clients' specific brand hues. In particular, the prepress operator must determine if and when to separate specific design elements into spot colors instead of CMYK inks.

 By separating into a spot color that is already being used, say for a Pepsi bottle label, De Roeck notes that the converter can achieve both qualitative and financial benefits. First, they reduce the number of inks on press, which simplifies registration issues; and they also decrease the consumables required to print the job, lowering the variable cost.

Similarly, six- and seven-color systems are used by a number of packaging printers/converters to reduce the wash-up, preparation and makeready times between jobs. And while FM6, Hexachrome, Opaltone, and other custom systems have proven themselves more than capable, you've got to correctly image the plates. While systems such as Artwork Systems' ArtPro and Esko-Graphics'

Scope can support these types of workflows, generic color management can generate separations with 1.5 percent dots and other anomalies that, while mathematically correct, cause problems once the plate is mounted on the press.

Beware barcodes?

 While there is much talk about how RFID will replace barcodes in the future, they're still a critical part of every package. Typically, converters print barcodes using the darkest solid ink to insure the scanner can read it at the checkout. To do this, however, the prepress workflow has got to be able to isolate that element?and possibly others?so that it does not separate into multiple inks in the process of converting to a multi-ink process standard like those mentioned above.

While not directly related to CTP, barcodes represent an opportunity for the packaging prepress service provider to become more tightly integrated into his customer's supply chain. Sure, there are plenty of software tools available for creating barcodes, but if your prepress system can be integrated into your customers ERP system to automatically "pull" the correct barcode, then you can reduce cycle time and eliminate errors.

 The barcode example underscores the need for workflow optimizations, all focused on error reduction in the prepress workflow, ultimately resulting in cost reduction. Beyond "pipelines," however, successful workflows will increasingly migrate into the customer's office, whether for pricing downloads or the latest FDA-approved label information.

The proof is in the proofing

 Perhaps the most visible change related to CTP is in proofing. Digital proofers of the Epson variety demonstrate a broad gamut and outstanding detail. Beyond calibrating colors to match the press/ink/substrate combinations, however, you've got to show how opaque text objects will interact with transparent inks.

Increasingly, softproofing is being used for this step. Systems such as KPG Matchprint Virtual, Artwork System's WebWay and Esko-Graphics' WebCenter all provide browser-based viewers. These provide users with the ability to check one or more 1-bit TIFF files to see exactly how the screens are going to interact, and how the traps will print. In future, hardcopy proofers will likely handle the color fidelity issues for the consumer package-goods firms, while softproofers will let prepress and print folks insure the dots and spots print correctly.

There are also some powerful 3D rendering tools available. Esko-Graphics offers a browser-based VRML tool that "folds" a 2D drawing into a 3D package. Integrated Color Solutions offers a rendering capability that lets clients rotate packages around all three axes to see what the final package will look like. Again, it's all about becoming part of the customer's supply chain.

Whereas anamorphic distortion has long been part of the packaging prepress workflow, today we also have its inverse. With shrink wraps and unusual sleeves increasingly common, you need to see what those distorted images will look like once they are shrunk and/or wrapped around the container.

Among the tools designed for this task are Artwork Systems' PowerWarp utility.

Although imaging in the round, or making cylinder sleeve plates, is just beginning to hit the market, a few have made the investment. For them, there's the issue of seamless screening?matching dots where the image begins/ends. I'd love to hear how to do that.

Final output (almost always to a 1-bit TIFF) is not significantly different from CTP to film. The curves are different, but you still converting vectors and bitmaps into binary files. Yet since CTP enables the press to do much more, you must account for this in the screening. Today's consensus is that transitional screening, with stochastic for highlights and shadows and conventional halftone dots in the midtones, is the way to go.

CTP for flexo is still in its infancy. The technology is proven, but the economics have yet to reach a point where most prepress service providers and package printers can justify the investment. It offers the ability to print a better package-you've just got to set up the workflow to take advantage of its capabilities.

Alex Hamilton is founder and president of Computers & Comm. Consulting, Inc., Philadelphia. He can be reached at 215/247-3461, e-mail: info@candcc.com.