21 March 2008

How to Convert Files to CMYK

All computer monitors emit colour as RGB (red, green, blue) light. Although all colours 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 colours. Like monitors, printing inks also produce a colour 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 colour or must be converted from RGB colour to enable use.

Many graphic programs have the capability to convert the layout/images from RGB to CMYK. In order to make sure that the final result meets your expectations, it is imperative that you set your graphics to CMYK whenever possible. Most desktop publishing programs allow you to do this quite easily.

• In Adobe Photoshop - open the file go to image - mode - cmyk.
• In Adobe Illustrator - Select all - filters - color - convert to cmyk.