Today, promotional graphics demand process color. Can your screen-printing shop deliver?
By Bruce Ridge
Many of these problems could be avoided if screen printers gave more consideration to viewing distance. In other words, how much detail do we need to provide so that the image looks good at the distance from which the graphic is designed to be viewed? A great deal of process-color screen printing is done at resolutions that far exceed what the viewer will be able to see when the graphic is mounted or hung. Employees need to be taught how to determine the best resolution based on viewing distance, and sales people need training on how to demonstrate this concept to customers.
Training should also cover the main influences on process-color accuracy: tonal range, gray balance, and color correction. Printers should understand how to address each of these factors through color management. They need to be familiar with the concept of linearization, which involves determining the reproducible tonal range of each output device (imagesetter, printing press, etc.), then adjusting the tone curves of each separation to compensate and ensure an accurate and predictable printed result. They also need to understand how and why to make gray-balance evaluations and adjustments to provide the right balance of color across the entire image.
Test images and printing to acquire the data on which to assess linearization and gray balance, printers must create, print, and evaluate suitable test images. These images can be created, purchased, or \"borrowed\" from a number of sources throughout the graphic-arts industry.
If things are slow in the shop, creating such a test image from scratch can be a valuable and educational experience for printers. It's also an effective way to evaluate the print process as well as new products (inks, substrates) you may be asked to print. To assess test prints, printers must be trained in the use of various measuring devices, such as transmission and reflection densitometers.
The practice of generating, measuring, and evaluating prints has been adopted by all the other printing processes as a valuable way to understand and improve image quality. However, the whole concept of printing test images, reading the results, and making changes to improve future print jobs is very foreign to screen printers.
The training environment
Did you enjoy this article? Click here to subscribe to the magazine.