Printing Basics: Color
FULL COLOR aka PROCESS COLOR aka CMYK
In the printing industry four colors are used to produce all the colors in the rainbow: Cyan (blue), Magenta (red), Yellow and Black (K) (called “CMYK”). You must start with a CMYK image or convert your RGB image to CMYK in order to produce a printed product. You can convert your RGB images to CMYK using an image-editing application such as Photoshop, Corel PhotoPaint or another pixel-based editing application.
RGB to CMYK Color Conversion
Files that have been created in RGB will need to be converted to CMYK because it is not possible to produce ink on paper printing from an RGB image. Files that were created in RGB and converted to CMYK will have a color shift. On some designs it is not very noticeable. On others the shift will stand out. During a color conversion all colors change from being built from 3 colors to being built from 4 colors. The colors are also changed from projected light to reflective light. We prefer that our customers convert their RGB images to CMYK, therefore they have control over the final outcome. We will convert files for a nominal charge.
Use caution when you have a solid area that is Black. Four-color process (CMYK) should be used to create a deep, dark, black, however if the total percentage of all four colors is greater than 340% your document will not print properly. Ink will saturate the stock and you will not be pleased with the final product. The only exception to this rule is text, please see the Black Text / Font section. Please use these settings when designing your document.
The optimum settings for Black are:
- 100% Black
- 75% Cyan
- 70% Magenta
- 40% Yellow
Black Text / Fonts:
When creating black type please give it the following CMYK break down:
- 100% Black
- 0% Cyan
- 0% Magenta
- 0% Yellow
When to Use Full Color Process Colors (CMYK)
- Publication uses full-color photographs.
- Publication includes multi-color graphics that would require many colors of ink to reproduce with spot colors.
- Needs more than two spot colors (process color printing can be less expensive than using three, or more spot colors).
- Projects with bleeds, hairline registration, heavy solids and custom color mixes can often be less expensive with full color
SPOT COLOR aka OFFSET PRINTING
This process is usually used with one- or two-color printing. Spot colors are specially mixed inks that come in a rainbow of colors, including some specialty inks such as metallic and fluorescent. Unlike CMYK (or process color) which creates colors by laying down layers of cyan, magenta, yellow, and black in varying amounts on the printed page, spot colors are pre-mixed and applied individually to the printed page. Most printers have a standard selection of Pantone® colors, with special Pantone® mixes available for an additional fee. For offset printing, design your piece in black & white or grayscale. Your color will be applied on the press. For two-color projects you will need to provide color separations. You can either do this by assigning a Pantone® color to each element or you can provide a separate page for each color. Crop marks and registration marks should be used to ensure that your colors line up properly.
If two different colors come within 1/16” of each other, this is called close registration. Hairline registration is when two colors actually touch at the edges. Both close and hairline registration require special attention when preparing the color separations and during the printing process and therefore will cost more. Please let us know in advance if your project uses close registration.
- Minimum image requirement of 300 dpi for this process.
- Screens are usually best between 15% and 85%.
- Halftones can be provided as grayscale images. It is no longer necessary to apply halftone screens to photos.
- Color separations must be provided for two-color work.
- Colors should not overlap, and hairline registration requires “trapping.”
When to Use Spot Colors (Pantone® Matching System)
- Publication has no full-color photographs and uses only one or two colors (including one spot color plus black).
- Publication needs a color that cannot be accurately reproduced with CMYK inks, such as precise matching of a corporate logo color.
- Need more vibrant colors or more exacting color matching than what CMYK inks produce.
- Project requires special effects such as metallic or fluorescent spot inks.