The simple rule of thumb to remember is that CMYK should be used for jobs that are going to be printed and RGB should be used for jobs that are destined for the web or other digital methods of delivery that display on a monitor.
Using the wrong color space for the job at hand can throw up problems, though in many cases these may be quite minor and not obvious to the eye.
When to Use CMYK
CMYK is a subtractive color process that is used in the press production of most printed materials. It works by combining four inks to produce the effect of many other colors in the human eye. The four inks are cyan, magenta, yellow and black, also referred to as the key, hence the acronym CMYK.
An RGB job maybe printed on most desktop printers without any problems, but this is not the case when the same job is sent to print on a commercial press. In that case the job is converted by RIP software into the four separations from which printing plates are produced.
If the job hasn't been set up in the CMYK color space, the RIP can't split the job into the four CMYK separations and this may lead to problems in the finished print. One common example of this is when an RGB image has been included in a CMYK document, which may result in the image printing as a grayscale image instead of the intended color version.
When to Use RGB
RGB works by combining red, green and blue light to produce a wider range of colors. The point that does seem slightly odd is that as more of each color that is added, the resulting color gets lighter. In fact when all 3 colors have been added together at their maximum values, the result is pure white.
RGB is used for jobs that are intended to display on a computer monitor or other types of screens, such as a mobile phone. In general, colors in RGB tend to be brighter and when an image is converted from RGB to CMYK, the converted image will often appear visually duller.
RGB files have smaller file sizes and if a job isn't destined for reproduction on a commercial press, working in RGB may be quicker. It should be noted, however, that if a job is printed from RGB, the colors may appear different to how they appear on screen, though there are other factors that may also play a part in this, including the calibration of the monitor that it is viewed on.
When a Graphic Designer starts work on a new job, they should consider how the final job is going to be distributed and use the appropriate color space from the start. It's also essential that any images that are being used should also be converted to the correct color space before being included.
Ian Pullen - Ian Pullen is a Graphic Designer with some 15 years of experience in the industry. His first foot on the ladder, after completing 2 years ...
