About Color Separation
Color Separation is the process of converting an image, such as photograph or full color artwork, into a set of spot colors that can be printed easily.
Color separations for screen printing are always done using Adobe Photoshop along with a plugin such as UltraSeps or QuikSeps.
When an image is brought into Adobe Photoshop, its usually in a color mode compatible with the device that it was created with such as the RGB color mode. RGB is a common mode for digital cameras and computer monitors.
The RGB mode is based on the blending of Red, Green and Blue light. To screen print an image, the colors need to be converted to a combination of spot colors compatible with screen printing. The resulting set of colors is called a Color Separation.
There are many types of color separations available to t-shirt screen printers.
Types Of Color Separations Commonly Used
Simulated Process Color
This is the most common type of color separation and is by far the most popular. Most of the color separations done today are simulated process. Simulated Process separations, unlike true process (CMYK) use spot channels and regular plastisol inks to generate a full color image. Simulated Process can be printed on white, light and dark shirts and look equally great on all. If unsure about the type of separation needed, run simulated process.
True Process Color – CMYK
CMYK Process Color uses cyan, magenta, yellow and black process inks to create a realistic photographic image on the t-shirt. CMYK separations are great for true photographic images or pastel style artsy graphics such as a painting. Some CMYK separations require an added spot color to help the image print accurately. This type of separation isn’t a good choice when printing on black or dark shirts or when a bright, vibrant print is required. Its also not a good choice for an image which contains large areas of solid, defined different colors.
Index Color
Unlike other separations, Index uses tiny square dots of identical size as opposed to traditional halftones. Index separations work great on both dark and light shirts and are very easy to print and control on press. The downside to Index is that a good separation “usually” requires more colors to print accurately. Its also not a good choice for artwork containing excessive gradients or which fade off into the shirt. Index separations can appear grainy, especially on the computer monitor although will print great on press. If choosing Index, make sure the artwork is the “exact final size” being printed since Index Separations can’t be re-sized once complete. Start with artwork at 170 - 200 dpi when running an index separation.
Grayscale
Grayscale Separations are basically a simulated process separation done using a grayscale image void of color. They are also done on color images converted to grayscale for a different look. Quality grayscale separations include several gray ink channels a white highlight and a black. Sometimes the black ink is replaced by an “almost black” deep, dark charcoal color. Grayscale separations look great and are easy to print. The term Grayscale Separations can be a bit confusing as channels within a simulated process or CMYK separation are actually a Grayscale channel.
Spot Color
Spot Color separations are the type most commonly used since most artwork is simple such as jobs for schools, clubs, etc. Usually this type of separation is done automatically within an illustration program such as Illustrator. Sometimes however, an image can contain many spot colors and gradients and therefore attempting to output each color using Illustrator or CorelDraw can result in far too many films. This is where UltraSeps can help and bring that spot color job down to a manageable number of colors.
Discharge Ink Optimized
Discharge inks react with the dye in the shirt and basically replace the shirt color itself with the color of the discharge ink. The primary difference between Discharge Separations and traditional separations is the white underbase. With discharge, a white underbase under the top colors isn’t needed or wanted and there should only be white ink where white is actually seen in the design. UltraSeps includes a function to convert a traditional white underbase to a discharge white.
Duo-Tri-Quad Tone
This type of color separation is utilized when an image basically contains a single color along with its contrast. Think of a black and white photograph viewed through a red filter as an example. Its also used for sepia style images, such as the old photograph look whereas the photo isn’t black and white but rather has a faded tan and brownish look. Duo-Tri-Quad Tone Separations use multiple color channels to obtain the correct effect.
Photoshop Plugins such as UltraSeps are the most commonly used within the screen printing industry to generate high-quality color separations with Adobe Photoshop.
