More and more printers are venturing into simulated process screen printing. While this process has been around for more than 20 years, it generally requires a higher level of technical competency than basic vector art images. That said, halftone screen printing is within the realm of virtually any printer who wants to make the effort to move in this direction.

The original source file. (All images courtesy the author)

It’s relatively easy to create sim process artwork in vector programs like CorelDraw and Adobe Illustrator. The challenge comes when you move into Adobe Photoshop and develop the need to create simulated process separations from within the program. Photoshop has a steep learning curve and offers virtually unlimited possibilities in the hands of an experienced operator. Unfortunately, most printers lack the necessary skills to use the native program to create really good separations. This is where the plug-in and action-driven separation programs come in.

These programs range in cost between about $300 and $900. There are a half-dozen programs available for both Mac and PC. Each approaches the task at hand with its own strategy and delivers separations with varying degrees of accuracy. Without going into specific comparisons between solutions, I’d like to provide an overview of some of the functions and provide some options for your own individual evaluation.

Simulation systems
There are two primary strategies for creating simulated process (more than CMYK) separations. The first is Index Color and the second can loosely be called expanded gamut or nChannel separations. We’ll begin with Index Color.

With this approach, the production artist or color separator makes a selection of colors based on the dominant colors in the image. Photoshop then uses a diffusion dither algorithm to reduce the total number of colors in the image down to the selected palette as defined by the artist. The results can vary from spectacular to dismal. (Editor’s note: See Photoshop Tips and Tricks on page 56 for more on Photoshop.)
 

Here, the original image has been separated as multichannel and Diffusion Dither halftone applied.

The limitations of this process are in the number of colors selected. Think of it as a high-tech version of paint by numbers. The software creates a jigsaw puzzle of colored pixels based on the colors selected. Each pixel color represents the chosen ink color. The program does the best job it can of trying to make colors based on the selected palette. The pixels do not overlap. They are side-by-side and create 100 percent ink coverage of the image. From a distance, the eye mixes the colored pixels creating the appearance of a full-color image.

This process works best if you have at least a 10-color press. With less than 10 colors, there is most often only a reasonable approximation of the original image. In addition, it is not possible to make localized color corrections if the color separation is off in part of the image. You’ll have to go all the way back to the original art, select a new palette, re-separate, run new film, burn ALL new screens, and set the job up again. This is the single biggest drawback to index separations. You need to have good color experience and understanding to make the right selections in the first place.

The strength of this type of separation is in the ease of printing. As long as you can hold good register, you can achieve very good, consistent results. It works very well on dark garments and utilizes easy-to-print opaque inks. If you can live with the approximate results, you will more than make up for them with ease and consistency of printing.

Simulated process separations are the second option, and, in my opinion, offer the greatest opportunity and flexibility. All of these programs begin with an RGB to CMYK conversion and are followed with the extraction of the secondary colors, and sometimes tertiary colors, to create a multichannel (nChannel where n= number of channels) separation.

The primary colors are cyan, magenta and yellow. Secondary colors are red, green, and blue. The tertiary colors are generally neutral colors like grays and browns. Sometimes they are designated as “fleshtone shades.” This is a very common approach to the extraction of color for control purposes.

It is possible to create new blank channels in Photoshop and use the Color Range option under the Selection menu to extract specific ranges of colors from the original image. These selections are placed into their own channels to be printed with their own dedicated ink colors. This is the option chosen by most experienced color separators. But what if you lack experience? This is where the plug-in or action-driven separation software packages come in.

Separation automation
The makers of plug-in separation software have chosen color sets and have automated the color-separation process. These are sometimes referred to as “push button” separation programs because that’s all you have to do. As attractive as this sounds, they all come with limitations.

Clearly the biggest of these are the underlying assumptions used by the programmers as to how they select and extract the colors. To my knowledge, none of the lower-end (<$1,000) packages use the more sophisticated algorithmic programming available in high-end packages. What you save in cost is reflected in the accuracy of the separation. For images with noncritical color, these programs work fairly well to excellent, depending on the image. For images where pleasing, non-reference color is all that’s required, they are an excellent choice. The closer you get to specific or reference color, the more limited they become.

When we speak of specific or reference color, we are talking about hitting a specific color as designated by the client. These would be logo colors, Pantone Colors, or colors we know to be familiar and recognized. This is where the extraction method falls apart. In order to adjust the separation to hit these target colors, you will need a companion plug-in that allows for editing and mixing the specific colors in each channel. There are two programs available that will allow you to do this.

The first is available for Mac and PC and is called VueRite. It is part of the Freehand Graphics SPVR software. The second option is from Aurelon Software and is only available on the Mac platform. This software is called CoCo. Both programs are extremely valuable as they allow users to edit the separation after it’s been rendered. This is absolutely critical to success when working with reference color originals.

Color theory
The two biggest challenges I’m asked about the most by printers using desktop separation software have to do with ink color selection and dot gain on press. Let’s talk about ink colors first. Each vendor has made their own choices as to the ink color palette they have chosen. However, you’re not locked into these colors. It’s possible to make adjustments to the ink color on press instead of having to go all the way back to the original if you aren’t getting the results you want.

As an example, popular programs use Pantone 123 as their choice for yellow, which is more of a red shade of yellow than a classic pure yellow such as Pantone Yellow. The warm shade (123) may have an affect on cool color mixes such as pastel and lime greens, rendering less saturated, muddy colors. If you do not have any orange or gold in the original you can even go so far as to use Pantone 395 which now shifts the yellow to a green shade, thereby enhancing and intensifying the greens in the image.

The second major challenge is in properly setting the dot gain correction within Photoshop to get a proper display of how the image will print. If you don’t do this, you are guaranteed hours of frustration. This is done in Photoshop under Color Settings >Advanced>Dot Gain> Spot Color. Set the value for 88 percent in the 50 percent box. For a detailed discussion on exactly how to do this, download my Top Ten Quick Start Guide to Better Halftones available at http://www.halftonesecrets.com.

Color is a lot like cooking. Taste is individualized and can be general or very specific. In order for you to better understand color mixing and color theory, you’ll need some education. One of my favorite books is Blue and Yellow Don’t Make Green by Michael Wilcox (ISBN 0-89134-622-8). This is an excellent starter book on color theory and practice. The more understanding you have about color and how color works, is perceived, and how it is reproduced, the better your results will be and the easier it will be to get excellent results from your separation software.