Specifications

The Digital Fine Print Course

Editing a Fine Print

Colour Correction Tools

To fully colour correct an image control is needed over six variables:

1. Hue

2. Saturation

3. Brightness

4. Density Range

5. Global Colour Balance

6. Local Colour Balance

Photoshop’s Colour Picker displays a 2D

representation of 3D colour space.

Hue:

The hue of a colour is what is often thought of as the actual colour or ‘colour of the colour’

and is described by its (hue) angle on a 360º colour wheel. For example red has a hue

angle of 0º, green 120º, and blue 240º.

Saturation:

Saturation or Chroma is a second defining characteristic of colour. It defines the purity of

colour and is expressed as a percentage where 100% is the most saturated colour that

can be reproduced on a particular device (scanner, monitor or printer).

Brightness:

Brightness is a third defining characteristic of colour. It defines the lightness or darkness

of the colour. In a monitor adding more light makes the colour lighter, while in a print

subtracting ink makes the colour lighter.

Hue, saturation and brightness represent the three dimensions of a HSB model of colour.

Any colour will have a certain hue, level of saturation and brightness precisely describing

its position (and colorimetric qualities) within its 3D colour space. For example, pastel

colours exhibit low saturation and high brightness values for a given hue. The Photoshop

Colour Picker provides a 2D ‘unfolded’ representation of device dependent HSB, RGB,

CMYK, Hexadecimal, and device independent LAB (CIE L*a*b*) models of colour space.

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