Chapter 4 32 Color When using photos, diagrams or other image elements in colour, these are printed in ‘full colour’, CMYK (Cyan, Magenta, Yellow and Key=black). These are the 4 basic colours used for digital and offset printing. RGB versus CMYK RGB colours are used for display and website design. These colours have a very high range in black and brightness. A printer cannot print RGB colours and therefore converts the RGB colour to a CMYK colour. Because the CMYK colour range is much smaller than the RGB colour range (see image below), RGB colours will be converted to the nearest colours in CMYK that can be printed. However, this can cause colour surprises. Compared to the colours of your file (in RGB) on your screen, your file in CMYK on screen and especially in your print will be less bright and appear a bit ‘pale’. If you have access to professional software such as Adobe Indesign , Illustrator or Photoshop, try to work in CMYK colour mode as much as possible. This will give you a better visual representation of the final colours in your print. If your file is in RGB, we will automatically convert it to CMYK. So, your printed colours may look different compared to your screen. The different properties of various types of paper also mean that colours can look slightly different. In the back of this guide you can see what effect a particular paper has on a colour. The simplest and most effective solution to still know how your colour turns out, is a proof print. Use of black (rich black) When using large areas of black in your book or cover, use ‘rich’ black. This will give you a more deeper black color. Use these CMYK values; C60 / M50 / Y50 / K100
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