All About Print: Part 2 (Colour).

As the technology around printing continues to push boundaries, colour becomes more economical to print, thus allowing it to be a very permanent fixture in all visual communication from newspapers and magazines to large format wallpapers and billboards. With the advent of low-cost full colour printing and developments like six-colour hexachromatic printing, colour is affordable and it is everywhere. This is why it helps to have a basic understanding of colour, especially if you are a professional designer or even a hobbyist, as colour is one of the most important tools in graphic design. Not only are there an almost infinite number of variations available at our disposal, but there are countless ways of combining them across many different types of media.


Basic Terminology

You’ll hear a lot of different terms thrown around when talking about colour. Here, we’ll investigate some of the more useful ones. To break it right down, there are basically three different ways to describe colour: Hue, Saturation, Brightness.

  Hue

Hue

Hue refers to a unique colour’s name that helps us visually distinguish between one colour and another. Basically, it is the generic name of the colour - for example, red, blue, yellow.

  Saturation

Saturation

Saturation essentially means how pure or how grey a colour is. Not to be confused with how light or dark it is (see Brightness below). Saturation describes if the colour is high intensity - pure and bright, or low intensity - dull and grey.

  Brightness

Brightness

A single hue (colour) will have a huge amount of variations ranging from light ‘tints’ to dark ‘shades’. The more white that is in a colour, the lighter it becomes, and it is known as a tint. On the other hand, a colour with more black in it becomes darker and known and a shade.

Hue, Saturation and Brightness can be manipulated easily using image editing software and designers can now easily change the entire appearance of an image in a matter of minutes.


The Colour Wheel

  RGB

RGB

The colour wheel shows primary, secondary and tertiary colours, and a full wheel will also show tints and shades of these colours (as above). Primary colours are red, yellow and blue - this is not to be confused with colour ‘models’ used to display colour on screen or in print (more detail on this below). Secondary colours are produced by mixing any two primaries together, resulting in orange, green and violet. The six tertiary colours are made by mixing a primary colour with the secondary colour closest to it on the wheel, producing red-orange, yellow-orange, yellow-green, blue-green, blue-violet, and red-violet.

So we now have access to 12 fairly basic colours, and once we add their tints and shades to them (as in the image above), the choices start becoming endless!


Additive And Substractive Primaries

 RGB

RGB

In order to have a good understanding on how colour works, it is essential to know that coloured light and coloured pigment do not operate the same. Coloured lights, or ‘additive’ colours, are represented by the RGB system. Coloured pigments, also know as ‘subtractive’ colours, are represented by the CMYK system. Put simply, when viewing an image on a screen, which is made up of coloured lights, it may not appear the same as when it is printed, using the CMYK system.

RGB stands for Red, Green and Blue and it is an additive colour model where red, green and blue light are added together in various ways to reproduce a broad range of colours. When all three colours are added together, the result is white light. As mentioned above, the RGB colour model is used to represent images on screens such as televisions, computer monitors and displays on devices such as smart phones and tablets. Cameras and scanners capture images in RGB.

 CMYK

CMYK

RGB is what is known as a ‘device-dependent’ colour model. This means that different displays will reproduce a given RGB value differently - so what RGB colour I see on my computer monitor can differ to the colour you see on your computer monitor, and again on your smartphone. It is important to remember this when designing and also when sending and viewing design proofs.

The range of colours produced by a colour model is known as it’s ‘gamut’. The RGB colour gamut can reproduce around 70 percent of the colours visible to the human eye. The CMYK colour model can’t reproduce as much as RGB so when designing be aware of this limitation. It is a common mistake of designers (both hobbyists and professionals alike) to submit artwork for printing in RGB. The results upon completion can be slightly underwhelming! RGB is able to reproduce brighter, more saturated colours simply because it is based on light. Your monitor is not a piece of paper!

RGB is used for anything that will be displayed on-screen for example; websites, apps and web advertisements.

CMYK stands for Cyan, Magenta, Yellow and Black and it is a subtractive colour model used for colour printing. Inks in the CMYK model ‘subtract’ brightness from the white or brightness of the paper, reducing the amount of light being reflected. CMYK is the opposite of RGB where white is the natural colour of the paper and mixing the coloured inks together results in black. The ‘K’ in CMYK stands for ‘Key’ - when printing, the three colours Cyan, Magenta and Yellow align with the Black, making it the ‘key’. Another way of explaining it, although not correct, is that because ‘B’ is already being used by Blue in RGB, ‘K’ is used as it is the last letter in Black.

The important thing to remember is that the CMYK colour model is also ‘device-dependent’, so colours can vary from printer to printer. As is the case with RGB, CMYK only reproduces a subset of the spectrum visible to the human eye. As mentioned in RGB above, the gamut of CMYK is less than that of RGB, making it a difficult proposition to design a printed piece, as you are viewing it on an RGB screen.

In colour printing, the four colours of CMYK mix together to create millions of colours. This process is often referred to as ‘full colour printing’ and can also be known as ‘four colour printing’.

We will cover CMYK and printing in more depth when we discuss the different printing processes in the coming weeks.