CMYK or Full Colour Process Explained


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What is RGB Color?

Scanner and digital cameras create images using combinations of just three colors: Red, Green and Blue (RGB). These are what’s know as the primary colors of visible light and this how computers and televisions display the colour that we see. RGB colours will appear more vibrant as light is being ‘transmitted’ or being projected directly into the viewers eyes.

These 3 colours when combined with different amounts make up all of the monitor or TV pixels that you see.

Many computer software uses RGB as a default as desktop monitors display this colour themselves. Desktop printers and laser printers also use this 3 colour technique in order to simplify the output of a printed sheet.

What is CMYK or Process Color?

CMYK or Cyan, Magenta, Yellow and Black are used in the industry standard colour mixing techniques to achieve full colour printing of just about everything form A5 leaflets and flyers, to full colour brochures and newspapers. Have you ever noticed on the back of a newspaper that there are several blocks of colour, these are used for registration of the four colours. When CMYK are mixed in the correct proportions they produce millions of colour possibilities. Sir Isaac Newton developed the technique over 300 years ago, using the CMYK which are directly opposite the RGB on a chart known as Newtons ‘Colour Circle’.

Full colour printing presses use CYMK inks in a subtractive process to absorb light which is then reflected from the white of the paper or card underneath. In a very similar method to mixing paint like a child would do at school, i.e red & yellow mixed together make green, the ink used in varying density to create the desired result. This technique is also known as Four Colour Process or Full Colour Process and has been with us for many years.

The range of colour that CMYK can produce is vast, but it has a limit as is not as wide a range as that of RGB. As a direct result of this bright colours with intense colour values such as Orange, Green, and Blue can sometimes appear to dull or sometime dirty, however red will appear almost the same with either process.

Most professional colour printing companies will be able to reproduce almost every colour imaginable, but for those specific colours which are not available in CMYK, then the printer will usually use a ‘SPOT’colour.

RGB Must be Converted to CMYK Color in Order to Print

Images photographed using a digital camera are usually saved using RGB. These will need to be converted to CMKK before they can be printed using full colour process. Most image software is capable of doing this, however there can be some slight shift changes in the colour when it converts, these can easily be addressed by adjusting the contrast and brightness etc.

Colour charts can be used for converting rgb colours into CMYK, and PANTONE is the industry standard. Pantone supply various colour matching books in particular the Pantone Colour Bridge set, which have the RGB colours next to the CMYK equivalent making it easier to match them.

Danny Molt is an avid writer and follower of the developments in Leaflet Printing and Printing Services
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