Color separation is the process by which the original full-color digital files are divided into separate color components for four-color process printing. Each element in the file is printed in a combination of four colors: cyan, magenta, yellow and black, known in the world of commercial printing as CMYK.
By combining these four ink colors, a wide spectrum of colors can be produced on the printed page.
In the four-color printing process, each of the four color partitions is applied to a separate printing plate and placed on a cylinder of a printing press. As the sheet of paper moves through the printing press, each plate transfers the image to the paper in one of four colors. Colors — which are applied as minuscule dots — combine to form a full-color image.
CMYK color model is for print projects
The actual work of creating color separation is typically handled by a commercial printing company, which uses proprietary software to separate your digital files into four CMYK colors and transfer color-separated information to plates or directly to the digital press .
Most print designers work in the CMYK model to more accurately approximate the appearance of colors in the final printed product.
RGB is best for onscreen viewing
CMYK is not the best color model for documents viewed onscreen.
They are best constructed using the RGB (red, green, blue) color model. The RGB model has more color possibilities than the CMYK model because the human eye can see more color than ink on paper.
If you use RGB in your design files and send the files to a commercial printer, they are still separated into four CMYK colors for print.
However, in the process of converting colors from RGB to CMYK, what you see onscreen being color reproducible on paper can cause a color change.
Setting Up Digital Files For Color Separation
Graphic designers should install their digital files destined for four-color separation in CMYK mode to avoid unpleasant color surprises. All high-end software — Adobe Photoshop, Illustrator and InDesign, Corel Draw, QuarkExpress, and many other programs — offer this capability. It is just a matter of changing the preference.
Exception: If your printed project has a spot color, a color that usually must exactly match a specific color, that color should not be marked as CMYK color. It should be left as a spot color so that when the color is differentiated, it will automatically look different and be printed in its own colored ink.