When it comes to colour, a common frustration is the mismatch between what you see on-screen versus the printed result. Understanding why this is the case, can help you to navigate this issue. GSM compares the RGB colour gamut vs CMYK…
RGB Colour Gamut
To create colour, a device screen uses varying degrees of light, specifically Red, Green, and Blue light (otherwise known as the RGB Colour Mode). More than 16 million colours are possible using RGB—significantly more than what the human eye can distinguish (about a million).
RGB vs CMYK Colour Gamut
Compare this to the CMYK colour mode used in print, which can only produce about 16,000 distinguishable colours. Even if we add another 2,400 Pantone colours—print has a vastly reduced colour spectrum compared to RGB.
Any RGB colour which falls outside the CMYK gamut—will not reproduce accurately. Instead, you will get a ‘nearest’ approximation, which sometimes—is not a close match. To demonstrate this, if you create an Adobe Photoshop file in RGB mode and fill this with RGB Green (#00FF00)— then change the colour mode to CMYK; your green will be completely different. Photoshop has to reinterpret the RGB green into a colour CMYK can achieve—which, whilst still the same hue, is nothing like the original.
Practicalities
From a practical perspective, this problem manifests itself when RGB files or colours are present in print artwork—or—when a designer specifies colour from a screen without sighting a printed example of the colour. The printed colours may differ significantly from the screen versions in either situation. So, what is the workaround for this problem? Here are some suggestions:
- Firstly, understand that this is not the printers ‘fault’. RGB and CMYK are different colour models. Instead, change how you think about colour when working towards a print outcome.
- Do not use RGB Mode files or colours for print based projects, including Illustrator graphics or Photoshop images. When working towards print, use CMYK mode files and colours only.
- When specifying colours for print projects, choose these from a printed source such as the Pantone Bridge Guide or CMYK Colour Guide. The CMYK Colour guide shows thousands of CMYK breakdowns (without equivalent PMS colours). Using these tools to choose colour means the printed outcome will be very close to what you specified.
- Ask your printer to run a hard copy proof from the final artwork. A printer’s proof is the most accurate method of checking how the colours will print. If the colour on the proof is not what you expect, then you need to fix this before the project runs.
