This article presents an overview of a technique that involves the use of an inkjet printer to generate a series of continuous-tone progressive separations that will serve as visual guides on press.
By Joe Raymond
Printing has always relied on various forms of proofing to predict what an image will look like after it prints on a specific press. These proofing systems vary from simple to sophisticated, precise methods and devices. However, for achieving the best accuracy, proofing generally requires an investment in hardware, software, and training to produce the best outcomes.
In the past, screen printers wanting a visual reference for color targets relied on a color key—comparing the target to the actual process color as an image printed. The color key used transparent overlays made photographically in a dot-for-dot fashion. Each overlay had C, M, Y, or K (cyan, magenta, yellow, or black) pigments imaged onto individual acetates made from the same negatives used for making halftone films. Each colored film was layered to produce a dot-for-dot process printing proof.
A color key is one visual method for comparing the accuracy of a printed image to the expected image produced at press after each successive ink pass. Adjustments at press could be made after this visual comparison of the color key to the print in process as each pass is laid down, and in the same order that it prints. This comparison method is seldom used today because it is considered expensive, labor-intensive, and slow when compared to reading color control patches with a spectrophotometer – the most commonly accepted current technique.
The visual-color-key method remains valid, however, especially for less demanding process screen printing. And more screen-printing firms would be printing four-color process if they could simply stop thinking that four-color proofing requires an additional investment in hardware, software, and training just to get started. Delivering an inexpensive, fast, predictable and easily corrected method for visual proofing and print development using tools that most shops have already would incentivize those printers who have not yet tried it. This may be true for decorators in the industrial sectors who are looking for value-added process printing but lack the internal resources to train printers in these techniques—even if they were willing to make the capital investment to get started.
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