RGB VERSUS 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. Therefore for printed documents you must convert all RGB files to CMYK

Red, Green, Blue - Additive colors

Cyan, Magenta, Yellow - Subtractive colors

CONVERTING TO CMYK

At certain points during your work (or play) you will have to convert images from RGB to the CMYK color space. Any respectable image editor or file layout program has a option for it. Sometimes it can be tricky to fine the specific option to convert to CMYK.

Here is a list of several common programs with instructions on how to convert the color space to CMYK.

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.

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

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 Xpress

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.

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.

Is converting images to CMYK important?

Yes! It's very important if you are working on a print document. Commercial printers mostly accept RGB images without question but using images with a RBG color space can seriously mess up your image. Printers who accept RBG images auto-convert images to CMYK without checking the outcome.

Make sure you convert images to CMYK yourself, so you can do adjustments on the CMYK outcome if needed and keep 100% control over image quality.