October 19, 2012

RGB? CMYK? WTF?!

We often get asked why the colour on screen doesn’t quite match the printed version.

The difference is, one is creating color using light, one is creating color using the reflection of light off pigmentation.

Anything that is powered by light, (such as your computer, TV, iPad and mobile phone) uses RGB to create the image – Red, Green and Blue (the colours of light). The primary colours of light are known as ‘additive’ which just means that as you mix the colours they ‘add’ to one another – they become lighter. However, when printed, the complete opposite happens. Red ink on paper blocks all other colours and only reflects Red light. So when Red and Blue ink are mixed the result should be Black since neither Red nor Blue survive; each ink blocks the other.

That’s why, when we print we use CMYK to generate a colour – Cyan, Magenta, Yellow and Black. When using ink you are not using colours that emit light, but absorb light instead – hence they are known as subtractive colours. When these colours are mixed you don’t end up with muddy colours that you would if you printed using RGB.

But why is the letter ‘K’ used for Black? The letter B is already used for Blue and Black is often referred to as the Key colour as it is the strongest and is used to add weight and depth to an image.

Unfortunately, due to the technical limitations of CMYK inks not being able to be made as pure as the colour values of light, you end up with less of a colour range. That’s why you might be able to achieve a certain colour on screen but not in print. Also the contrast range in printing is limited to the black of the ink and the white of the paper which is much less than the range of an RGB computer monitor.

So… if you’re having something printed, what you see on screen is not always what you get. The best way to ensure you get your desired result is visit your designer and take a look at their swatch books. That way we can avoid any disappointment and ensure the correct colour is printed.

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If only we had a Crystal Ball…