spot color separations-
Spot color images generally have specific solid colors that can also be made of small dots called halftones. Spot color separations/prints are generally used for logos, school designs, clipart, hard edges graphics, cartoons or other images that have a black or dark outline.
A spot color image can be as simple as one-color and as complex as 14 colors, and can include lots of shading, gradations and detail. They still generally have a flat, cartoon like look and are not photorealistic.

Spot color separations are done in vector based programs like CorelDraw, Adobe Illustrator and Macromedia Freehand.

process color
Process Color images are made up of the colors of cyan, magenta, yellow and black. Process color prints are generally referred to as CMYK (the "K"; is for the "key"; color of black). All of the photos in magazines like Impressions are made of these four colors. If you took a magnifier to these images you would see that they are made up of small halftone dots that when printed make up most of the colors of the rainbow.

If process color will print all these colors then why not use it for all your designs? If a T-shirt image were not photorealistic why would you want to print four colors when for a simple "spot color"; image only two would do? Also, for most of your spot colors images you need a more vibrant, solid image rather than a soft halftone dot print.

Process color prints on T-shirts generally only work well on light colored shirts. The inks used are very transparent and do not work on black, and when printed on an underbase of white ink, will become very pastel.

The problem with printing process is that if you are not a good printer or don’t know how to do the separations, the images will be muddy when printed. Although process color separations are generally done by pixel based programs like Adobe Photoshop, these programs were designed for paper/offset printing and the program settings don’t allow for the fact that halftone dots grow in size when printed on a soft object like a T-shirt (dot gain). Process color separations are generally NOT done with vector based programs like Corel Draw.

For this reason, process color is not for everyone. It generally needs better control like properly tensioned, high mesh-count screens and the ability to hold fine halftone dots and print them in register with minimal dot gain. The secret to good process prints is in proper separations and good printing. Yes, you can do it, but plan to experiment a little.

When you see a hot process color print, it almost always has additional spot colors. What you think is just a cmyk print may in fact have cmyk plus two or three spot colors to make the design really jump off the shirt.

If you don’t know how to do the separations you should either use an industry specific color separator, follow directions from articles in this magazine or download how-to-do-it articles from www.screenprinters.net/articles, or use industry specific separation software.

simulated process color
This is also known as "fake"; process color. Simulated Process color images have a photorealistic look but are not printed with the process colors of CMYK. They look like process, smell like process, feel like process but aren’t process. The color separations for simulated process color are made up of halftone images of spot colors like red, yellow, blue, etc. They are often called "tonal"; or "channel"; separations. Simulated process separations can be printed on light and dark shirts and are generally done in Adobe Photoshop.

Because the inks for simulated process color are generally all-purpose, semi-transparent plastisol they give you a bright print even when printed on an underbase of white ink. When done correctly, simulated process prints can be very photorealistic with smooth gradations and bright colors.

index color
This is probably the most confusing of the separation methods. For simulated process, real CMYK process and spot colors with gradations, any shading is done with different size halftone dots that have a definite pattern and angle to them. Index separations are done in Adobe Photoshop and use a random square dots that are all the same size. These random dot patterns are also often called diffusion dither or stochastic.

In theory, index separations should not give you a moiré pattern because the dots are all the same size and they are random. Yes, you will not get a moiré pattern within the separations but if you use the wrong screen mesh (200 dpi index separation on a 200 mesh) you will probably get a bad moire.

Index color separations are done in Adobe Photoshop by creating a color table of the most prominent colors in your image (and the most colors you are capable of printing) and then letting Photoshop convert the image to just those colors using random square dots. Photoshop will make (or try to make) the image look as close as the original as possible with just the limited number of colors you selected.

Index prints can be very bright on light and dark shirts and the separations are easy to do. The downside to index prints is that for the image to be photorealistic you need at least six colors and in some cases eight to ten colors. Index prints can sometimes have a grainy and textured look to them. When printed with a lot of colors index prints can also be very striking! Index separations work great for spot color images too. They are also easy to print because you are placing a dot next to a dot rather than printing halftone dots on top of halftone dots. Just don’t use indexing because someone told you that halftones are hard. Most of the award winning prints you see are still real process color and simulated process color.

CMYK process color
Great for photorealistic images on white or light shirts. Do not use on dark shirts. Requires good separations, screen making and printing technique. The best process prints have additional spot colors. Prints may be a little duller than a simulated or index print.

Simulated Process Color
Great for dark shirts that need a photorealistic image. Works on light shirts too. Requires good separations, screen making and printing technique. Can print very smooth gradations and hold excellent detail. The most popular method used by award winning printers. Prints are bright because all purpose inks are used.

Index Color
Works on light and dark shirts. Typically requires more colors than simulated or process color (especially if going on black shirts). Very easy to print because all the dots are the same size and you are printing square dots next to square dots rather than halftone dots on top of halftone dots. Separations are easy to do in Adobe Photoshop and screen making and printing can be forgiving. Very production friendly and easy to print. Images can have a slightly grainy look. Works well for spot color also