RGB and CMYK – which one for offset printing
RGB and CMYK are colour models used to represent and reproduce colours in various applications, such as digital displays, printing, and graphic design. They are both fundamental colour models, but they serve different purposes and are used in different contexts.
RGB (Red, Green, Blue) is a colour model that is used for electronic displays such as computer monitors, televisions, and mobile devices. It represents colours by combining different intensities of red, green and blue light to create a wide range of colours. However, RGB system is not directly compatible with printing because printing typically uses a different colour model called CMYK (Cyan, Magenta, Yellow, Black – sometimes called Key).
CMYK, on the other hand, is a subtractive colour model used in the printing industry. Instead of emitting light like RGB, CMYK uses inks. When printed, these inks are applied in layers to create the desired colours.
Why RGB system cannot be directly used for printing
Colour gamut
RGB has a wider colour gamut compared to CMYK. It means it can produce more vibrant and saturated colours that are outside the printable range of CMYK. When RGB colours are converted to CMYK for printing, some colour information may be lost or undesirably altered to the nearest equivalent, resulting in a less accurate representation of the original colour.
Device-dependent
RGB colours are device-dependent, meaning they can vary significantly between different electronic displays. The same RGB value may appear differently on various monitors or devices. In contrast, CMYK is more standardised in the printing industry, ensuring more consistent colour reproduction across different printers.
Light vs. ink
RGB colours are created by emitting light, while CMYK are created by subtraction and mixing inks. The properties of light and ink are fundamentally different, leading to variations in colour reproduction, especially bright blues and greens. They cannot be accurately reproduced using CMYK inks.
RGB vs CMYK – How to overcome differences
To overcome these differences, professional graphic designers should convert RGB colours to CMYK before sending the file to the printing house. This conversion helps to achieve a closer approximation of the original colours. Converting a file from one colour system into another can also be done automatically at a printing house. However, this approach carries some risks as you don’t have direct control over the final result.
By manually managing the conversion, you have more control over the colour representation and can make informed decisions to achieve the desired print result. This approach helps minimize the risk of unexpected colour variations or inaccuracies that can occur when relying solely on automated conversion methods.
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