Most graphics software programs give you the choice to work in either RGB or CMYK color. These are also called color spaces. There are color spaces other than RGB and CMYK but they are less common and we will not discuss them here.
- What is RGB Color?
- What is CMYK or Process Color?
- RGB Must be Converted to CMYK Color in Order to Print
- Converting Your Files to CMYK & Other Application Tips
- These Programs Do Not Have the Capability to Convert to CMYK
Digital cameras and scanners and create images using combinations of just three colors: Red, Green and Blue (RGB). These are the primary colors of visible light and this how computers and televisions display images on their screens. RGB colors often appear brighter and more vivid specifically because the light is being projected directly into the eyes of the viewer.
This is an "additive" process in which the three colors are combined in different amounts to produce various colors. It is called "additive" because you must add varying amounts of two or more colors to achieve hues and values other than the three basic red, green and blue colors.
Computer monitors and televisions vary the amount of each color from 0 to a maximum of 255. Equal maximum amounts of all three colors (often expressed as R255, G255, B255) creates white. The absence of all three colors (R0, G0, B0) creates black. Equal amounts of all three colors somewhere between 0 and 255 will create varying shades of gray.
RGB (additive) Color
Many graphics applications default to the RGB color space because computers use RGB to display color themselves. It is easier. Most software and even desktop inkjet and laser printers assume that you are using RGB color to simplify things for users. However, strange as it may seem, all desktop inkjet printers actually use CMYK (or at least CMY) to produce color documents. Not all printers use the black cartridge when printing color, the cheapest models may use equal amounts of Cyan, Magenta, and Yellow to produce Black (often poorly).
Based upon Sir Isaac Newton's Color Circle, Four color process printing was originally developed in the late nineteenth century along with the halftone process for reproduction of continuous tone images (photographs) and has been used for over 100 years to reproduce color images. The colors Cyan, Magenta, and Yellow appear directly opposite the Red, Green, and Blue on the Color Circle devised by Newton over 300 years ago.
Newton's Color Circle
Professional printing presses print full color pictures by using the colors Cyan, Magenta, Yellow and Black (CMYK). In this "subtractive" process the various inks absorb the light reflected from the underlying white paper to produce the colors that your eye sees. The colors that you see are those colors which were not absorbed by the ink. It is called subtractive because when you subtract the other colors, the color that is left is the color that you see.
In the CMYK color system equal proportions of Yellow ink plus Cyan ink produces Green, Yellow ink plus Magenta ink produces Red, and Cyan ink plus Magenta ink produces Blue (actually more like purple to most eyes). Various color shades and values are achieved by varying the relative amounts of the four colors. Black ink is added to improve the quality of 3-color blacks, to provide added detail to images, to speed drying, and to reduce overall ink costs, thus the name: Four Color Process.
CMYK (Subtractive) Color
This is the Four Color Process (also known as Process Color or Full-Color) printing that comprises the vast majority of magazines and marketing materials you see every day. Process color is generally very good for reproducing pictures but there are some types of color that it cannot reproduce well. This is because the gamut (or range) of reproducible color for Process Color is not as wide as that of RGB color. As a result, certain intense values of colors such as Orange, Green, Blue, and other bright colors can sometimes appear dull or even dirty. On the other hand, bright Reds generally reproduce very well.
That is not to say that CMYK color looks dull or dirty. Just look at any color magazine such as The National Geographic or fine coffee table book and you will see that it does a very god job of reproducing nearly every color that might be needed. For those special colors that cannot be satisfactorily reproduced by CMYK there is always spot color (special extra inks that are mixed to match a specific color or even a customized color). Spot colors are often used for metallic and other special effects colors.
It is best to select any colors you use for fonts or other design elements in your layout using CMYK definitions instead of RGB. That way, you will have a better idea of how they will appear in your printed piece.
At some stage your RGB file must be translated to CMYK in order to print it on a printing press. It is best if you do the RGB to CMYK Conversion of your images. You will have more control over the appearance of your printed piece if you convert all of the images from RGB to CMYK before sending them to us. Be aware that it is possible to create colors in RGB that you cannot reproduce with CMYK. These are beyond the CMYK color range or "out of the CMYK color gamut".
Here are some examples of how various RGB colors convert to CMYK:
RGB Colors (what you see on screen)
CMYK Colors (printing inks will do this)
You most likely won't notice this kind of color shift in a color photograph. It is more likely to happen if you pick a very rich, vibrant color for a background or some other element of your layout. It probably won't look bad, it just won't look exactly the same. But it may not be noticeable at all either.
To purchase a color guide with thousands of process colors with their RGB values and their CMYK screen percentages, please visit Pantone <link to Pantone here> to purchase swatch book. We recommend the PANTONE Color Bridge Set which contains both coated and uncoated stock ink swatches.
When we receive RGB images in a job we instruct our RIP software to make the conversion to CMYK. The RGB to CMYK conversion table tries to map colors to get as close as possible to the appearance of the original. We think that it does a very good job but it is possible that it might not be to your liking.
Here is an example: many programs translate the 100% Blue in RGB into a purplish blue color in CMYK (Adobe InDesign CS2 will give you C88, M76, Y0, K0). We suggest that you use a CMYK value of C100, M60, Y0, K0 to get a nice blue. Working in the CMYK color space allows you to select the exact CMYK mix that gives you the results you want.
We want you to be pleased with your job, so please, take the time to prepare your file properly. We cannot be responsible for results if you furnish your images in RGB. Even though monitors always use RGB to display colors, the colors you see on your monitor will more closely match the final printed piece if you are viewing them in the CMYK color space. Please refer to our page on monitor calibration.
For more information on converting your application files to CMYK and for other helpful tips on using these applications, please follow the links below.
- Adobe InDesign
- Adobe Illustrator
- Adobe Photoshop
- Adobe PageMaker
- Corel PhotoPaint
- Macromedia Freehand
- Microsoft Publisher
- Microsoft Word
If you use one of the following applications upon processing we will instruct our RIP to do the RGB to CMYK conversion automatically. We are confident that you will be pleased with the results.
- Adobe Photoshop LE
- Adobe PhotoDeluxe
- Microsoft Word
- Microsoft Excel
- Microsoft Powerpoint
- Microsoft Works
- Microsoft PhotoDraw
- Picture It Publishing