CMYK (Cyan, Magenta, Yellow and Black)
CMYK stands for cyan, magenta, yellow and key (black). It is a colour model used in colour printing, and is also used to describe the printing process itself.
See converting to CMYK.
The standard colour scheme for pictures is RGB (red, green and blue), and it is how we usually view images on a screen. The CMYK colour scheme (cyan, magenta, yellow and black) is used for print.
There are some colours that can be viewed in RGB mode that are impossible to achieve in CMYK mode. When you are preparing files for print, make sure that you are working in CMYK mode and make any colour corrections in that mode.
Always ask for a high-resolution proof copy before finalising your book for publication to ensure that your images are printed correctly.
There are some common issues when printing in CMYK, including:
- Blues being printed as purple. You should ensure that your cyan and magenta values are at least 30 points apart (for example, C100%, M70%, Y10% and K10%). When the values for cyan and magenta are closer than 30 points apart, the blues can turn to purple during printing even when they look right on your screen.
- Greys may not print as a neutral colour. This is because creating grey using all four of the CMYK colours can add variations to the grey. More magenta can cause a warmer pinkish grey, more cyan can create a blueish grey and too much yellow will produce a brownish grey. To overcome this, you need to make your greys using the black element of CMYK, which is K (key). Light grey can be achieved between 10-30%, medium grey between 40-60% and dark grey between 70-85%.
- Blacks may have a colour hue. This is similar to the grey problem. A standard, neutral black has the CMYK values of 60% cyan, 40% magenta, 40% yellow and 100% black.