Basic Colour Theory for garments testing.

Colour is a sensation that is perceived by the eye and communicated to the brain in the form of nerve pulses.

A coloured sample can be interpreted differently by different people and is affected by viewing conditions, eye fatigue and colour perception skills.

Although our colour perception is subjective, a basic understanding of the principles of colour will help us to communicate and evaluate colour in more objective ways.

For a colour sensation to occur, the following three ingredients must be present:

1)Light source – ILLUMINANT

2)Object – REFLECTANCE

3)Observer (the eye-brain combination) – STANDARD OBSERVER

Elements which cause the colour stimulus

Fig.Elements which cause the colour stimulus

Illuminant:

Illumination or light is essential to experience the sensation of colour.

When light passes through a transparent material, for example water, glass or a prism, the light is dispersed into the colours of the visible spectrum.

These are Violet, Indigo, Blue, Green, Yellow, Orange and Red.

The Visible Colour Spectrum

Fig.The Visible Colour Spectrum

White light is light that contains all the colours of the visible spectrum.

Scientists have defined the colours of the visible spectrum in terms of wavelength. The blue end of the spectrum having a wavelength of 400nm through to 700 nm at the red end. (1nm =1×10-9 metre. A nanometer is one billionth of a metre). These figures form the basis of Instrumental Colour Measurement.

All light originates from a light source of which there are two types, natural and artificial. Daylight is a natural light source whereas TL84 (F11) and Incandescent light (A), are examples of artificial light sources.

Each of these light sources is different and when used to illuminate the same object, different colour sensations can occur. This depends on how the energy of a light source is distributed.

Artificial Daylight (D65), is a cold light and most energy is given in the blue area of the spectrum.

Incandescent light (A) is a warm light giving more energy in the yellow and red parts of the spectrum.

Object:

The object is the physical sample (e.g. fabric swatch) that is being observed.

When an object is illuminated by a light source, several light-object interactions occur:

•The object REFLECTS light at some wavelengths

•The object ABSORBS light at some wavelengths

•The object TRANSMITS light at some wavelengths

•The object SCATTERS light at some wavelengths

For example, a red coloured sample will absorb most of the blue, green, orange, yellow light/wavelengths and reflect most of the red light/wavelengths.

It is the combination of these interactions that determine the object’s colour and appearance under that specific light source.

Observer:

The observer is the person that experiences a colour sensation as a result of an object’s interaction with a light source. The human eye receives the light/wavelengths, while the brain acts as its translator.

In colour science, human perception of colour (with ‘normal’ colour vision) has been named ‘The Standard Observer’.

Observers

Fig. color Observers

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