CMYK identifies the four colors used in traditional printing presses, and stands for, respectively, cyan, magenta, yellow, and black.

RGB refers to the so-called scientific hues--the additive primary colors red, green, and blue--that, when mixed together in equal amounts, create white light. Television sets and computer monitors display their pixels based on values of red, green, and blue.

While the more common decimal system uses a base of ten to represent all possible numbers, hexadecimal notation uses a base of sixteen: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, A, B, C, D, E, F. While such a system may seem confusing at first, it works extremely well in computing environments. For example, a single byte of information can be represented as eight bits (10011101), decimal numerals (913), or simplified to hex (9D). In hex, every byte can be shown as two hexadecimal characters.

As it relates to Web design, hexadecimal is the alphanumeric system used to specify colors in HTML. For example, the hexadecimal equivalent of white is FFFFFF, while black is 000000.

RGB vs. CMYK

Computer monitors emit color as RGB (red, green, blue) light. Although all colors of the visible spectrum can be produced by merging red, green and blue light, monitors are capable of displaying only a limited gamut (i.e., range) of the visible spectrum.

Whereas monitors emit light, inked paper absorbs or reflects specific wavelengths. Cyan, magenta and yellow pigments serve as filters, subtracting varying degrees of red, green and blue from white light to produce a selective gamut of spectral colors. Like monitors, printing inks also produce a color gamut that is only a subset of the visible spectrum, although the range is not the same for both. Consequently, the same art displayed on a computer monitor may not match to that printed in a publication. Also, because printing processes such as offset lithography use CMYK (cyan, magenta, yellow, black) inks, digital art must be created as CMYK color or must be converted from RGB color to enable use

All work should be in the CMYK (Cyan/Magenta/Yellow/Black) mode, as this is the mode required for the printing process. If an RGB (Red/Green/Blue) file is submitted, it must be converted to CMYK. When the conversion takes place, color shifts can occur and TSG will do our best to reproduce as close of a match to your printed output as possible.

It can sometimes be difficult to visualize the reason for color shift in color space conversion. The best way to see the color differences between the CMYK and RGB color spaces is to look at a color gamut comparison chart. The chart to the left plots the visible color spectrum as the large "horse shoe" area, and within this is a plot of the CMYK colors, and the RGB colors. You can see that in some areas the RGB color space is "outside" that of the CMYK space. It is these colors that will be affected by a conversion from RGB to CMYK

Most desktop scanners, digital cameras, and video capture systems save files as RGB and the conversion of RGB files to CMYK can be done in many ways. RGB converts to only CMY directly. However, when printing, we must add black ink and in doing so must cut back on some color. The Undercolor Removal (UCR) setup will help control this ratio so that a maximum ink density for the four colors will be 300% when printing on a coated paper stock.

Halftones

In offset lithography, the density of CMYK inks can not be varied in continuous fashion across an image, so a range is produced by means of halftoning. In halftoning, translucent CMYK ink dots of variable size are printed in overlapping grids. Grids are placed at different angles for each of the ink colors. Smaller halftone dots absorb less light; thus, as a result of an increase in the amount of reflected light, apparent density is decreased and the object appears lighter. Halftoning screen angles (133lpi 40% screen enlarged)

Converting files to CMYK  
(CYAN, MAGENTA, YELLOW, BLACK)

Here is a list of several common programs with instructions on how to make sure you are working in the CMYK color space. If your program or version is not listed here, don't worry. Most of these instructions will apply to all versions of a program. If at any time you need further help, please call us for assistance. We are happy to talk you through the steps needed to get your document into the CMYK color space.

Microsoft Publisher
Microsoft Publisher defaults to RGB. It is easy to convert everything to a CMYK color space or to start a new document using the CMYK color space.

Use the following menu options: Tools/Commercial Printing Tools/ Color Printing and select Process colors (CMYK). Please note that all images incorporated into a layout need to be linked and not embedded in order to maintain the CMYK color space within the image. Using the following menu options does this: Tools/Commercial Printing Tools/Graphics Manager and highlight the embedded image. Click Link and click Browse to locate the original file and link to it. You will then need to send both the images and the layout file to us for printing.

Adobe Photoshop
If the file already exists select the following menu options: Image/Mode/CMYK When starting a new file select CMYK for the mode before clicking OK.

Corel Draw
Select each object you want to convert. Select the Fill tool and click Fill Color Dialog. Make sure the Color model is CMYK. For each object with an outline: Select the Outline tool and click the Outline Color Dialog. Make sure the Color model is CMYK.

Adobe Illustrator
Use the following menu options. For an existing file select Edit/Select All and then Filter/Colors/Convert to CMYK. For a new file, select File/New and select CMYK color for the Color Mode.

Quark Express
Use the following menu options: Edit/Edit Colors/Show Colors in Use/Highlight Color and click Edit. Change model to CMYK and deselect Spot color. Remember to send us your layout and linked images!

Adobe InDesign
Use the following menu options: Window/Swatches and Window/Color. Double click color in Swatches Change color mode to CMYK and color type to Process. Any colors created in the document that are not in the Swatches palette, need to be changed to the CMYK color space. Select each object you want to convert and make sure the Color palette reflects the CMYK percentages. Click top right arrow in the palette to change to CMYK if necessary. Remember to send us your layout and linked images!

Adobe Pagemaker
Use the following menu options: Window/Show Colors. Double click "colors" in palette and select Model to be CMYK and Type to be Process. Please be advised that Pagemaker does not successfully represent CMYK color on the monitor.