WHY COLOURS CHANGE

We use colour models to describe colours we see and work with.  Colour models can be RGB, CMYK, and LAB etc.  

A colour space is a specific colour area in a colour model, and has a specific gamut or range of colour.

In RGB colour model there are several colour spaces i.e. adobe RGB, Apple RGB, SRGB.

They all have a different gamut or range of colours and all devices operate within their own colour space. I.e. the range of colours they can produce.

The monitor operates in RGB and the proofer in CMYK.  They both use a different colour model to describe the colour of an image.

Therefore we need to use colour management to change colours from one device to another so that the colours will be the same.

SOLVING COLOUR INCONSISTENCY

3 things must happen for a colour strategy to work.

1 Colour management strategy needs to know the colour space of the device that will create an image. This is done by measuring a profile chart to create a source profile.  This is the colour characteristics of the device that created the image.

2 The CMS remaps the source profile through a lab colour model which is a device independent colour model.

3 CMS must know the colour space of the output device. This is done by measuring a profile chart and generating an output profile.

Colour Management Systems

Colour Management System is a set of software, and sometimes hardware components in a computer designed to handle automatically the proper conversion of colours from  device to device. Each device is represented by a profile created either through calibration or characterization which dictates how colours are to be converted for that device

What is Colour

Colour can be defined as : ......

• ... a sensation!
• ... is made out of
• an object
• an observer (eye and brain)
• a light source

There are various psychological aspects to colour i.e.: Visual perception

• Light to dark contrast
• Quantity contrast
• Intensity contrast
• Warm and cold contrast

Measuring Colour

Density value is not enough to describe a colour and therefore each colour is described with the help of:

• Hue (H)
• Saturation (C)
• Lightness (L)

If you put each colour in a 3-dimensional model you can describe each colour with the help of numbers. The measurement of colours has to be done with a spectrophotometer (L, a, b)

L A B  describes how a colour looks and not by how much ink is needed by a device to make that colour.  colour management uses lab to translate a colour from one colour space to another colour space.

	L = LUMINANCE A = GREEN TO RED COMPONENT B = YELLOW TO BLUE COMPONENT
Polyflex can help you to understand and implement a successful colour strategy We focus on Standardised operating conditions from Design to Prepress to Press. The colour strategy developed can then be used in colour retouching via ICC profiles to press-simulated proofs. At the end of the day proofs (contract print) should not look nice - it should look like the print!