Colorimetry - Introduction

Light and colour and its use

• Light source colour• Colour of materials• Alpha-numeric information

– accentuation– ordering

• Graphical information– Characteristic colours

• Images– Colour correct visualization

What is colour?

What is colour?

• colour stimulus, visible electromagnetic radiation reaching our eye from the environment

• percept, produced by the stimulus in the receptors

• perception, produced in the brain

What is colour?• The rays

are not coloured

• Colour is a perception produced in the brain

What is colour?

• The stimulus originating in from the source is modified by reflecting/transmitting bodies

• The perceives, the brain processes the stimulus

Characteristics of the colour perception

• hue brightness/lightness satuartion

Production of the colour stimulus

• source

• body, modifying the radiation

• receiver

Sources

• Daylight

• Artificial lights

Mixture of coloured lights

• Additive colour mixing

• Perception in the visual system

Colour mixture in the CRT

• Emission of red, green and blue phosphors produce the colour stimulus

Brightness contrast

Colour contrast

The influence of the background

Further visual impressions

ASSIMILATION

SPREADING

• The background has the same chromaticity, only the colour of the lines is different

Effect of the sharpness of the contour

• In the middle of all patches the colour stimulus is the same

Perception of colour difference

• Effect of background on colour difference perception

Perception of deepness

• The red surface is perceived as being closer to us• Position of the surface can increase the effect

Coloured after-image

Coloured after-image

Sharpness – a psychological effect

The influence of the surrounding on sharpness sensation

Facial features

Facial features

Mechanism of human colour vision

• Structure of the human retina and its functioning – cones and rods– information processing in the retina

• Pathways to the brain, brain processing

• Colour vision deficiencies

Objective determination of the colour stimulus

Additive colour mixing Basics, Grassmann’s laws

RGB and CIE XYZ colour spaces

Transformation of colour spaces

• Standardized colour metrics

• 2°- and 10°-observers

Colour specification on the computer monitor

Colorimetry of self-luminous objects

CRT monitor characterization

Concept of correlated colour temperature

Object (surface) colours, uniform colour spaces and atlanta

CIELUV and CIELAB colour spaces

Munsell, NCS, Coloroid colour spaces and atlases

Concept of colour stimulus difference

– Colour difference metrics

Chromatic adaptation and colour appearance

• Chromatic adaptation – von Kries transformation– modern approaches

• Colour appearance, images on computer screens– Colour appearance models

• CIECAM97 model

Colour printing

Functioning of colour printers

Calibration of colour printers

Colour management

Further technologies

Colour TV

Colour film (positive - negative processes)

Colours on the Internet

Standards

• IEC TC 100 multimedia equipment

• ISO ergonomic & graphic art standards

• CIE vision – photometry – colorimetry standards

• TV and further standards

The use of colours on computers

• Small angle tritanopy

• Bezold-Brücke effect

• Helmholtz-Kohlrausch effect

• Colour induction and assimilation