Technical article – standardised light, April 2017, information supplied without warranty 1

Light is colour

Standardised light for consistent colour communication

Colour impression depends on the type of lighting. That means consistent colour communication is only possible when standardised light booths and proof lights are employed at every stage of the production process.

Colour is all around. Every object has a colour, which we naturally perceive –

provided light is present. Light is electromagnetic radiation, and whether its

wavelength lies toward the short or long end of the visible spectrum is what

determines our perception of colour.

It makes no basic difference if we view colour under a natural or an artificial light

source. However, the perceived shade will vary depending on the lighting

conditions. The colour of a light source is determined by its specific spectral

composition. Sunlight, for instance, differs depending on weather conditions, the

season and time of day. The colour composition of artificial light sources such as

fluorescent tubes and LEDs likewise covers a broad spectrum.

Technical article – standardised light, April 2017, information supplied without warranty 2

Colour impression in the printing process

Two people viewing the same print item under different light sources, such as

daylight and incandescent light for example, will perceive its colour differently. So

the type of illumination crucially influences the colour impression of an object.

The production process from initial design to finished print item or other

coloured material incorporates a number of checks and adjustments. In order for

everyone involved to see the same thing regardless of where they are situated,

the same standard lighting conditions must prevail everywhere along the

workflow.

Standardised light

has defined standard illuminants for the radiation spectra of different light types.

The printing industry uses standard light type D50 with a correlated colour

temperature (CCT) of 5000 Kelvin. Other industries – automotive, textile, paint,

etc. – all use D65 standard light.

Both standards correspond to lighting under average (northern) daylight

conditions. It should be noted that the definition of CIE standard lighting types

extends well beyond colour temperature alone. Thus, the CIE also assigns exact

chromaticity coordinates for a 2°/10° standard observer. That means a lamp with

a colour temperature of 5000 Kelvin is not necessarily a D50 standard light source

if it exhibits a positional deviation in the CIE UCS diagram.

Technical article – standardised light, April 2017, information supplied without warranty 3

Standardised colour checking

ISO 3664:2009 defines the international colour viewing standard for the graphic

technology and photography industries. It stipulates strict requirements

concerning:

– Colour quality

– Light intensity

– Uniformity of illumination

– Viewing conditions

Consistent colour communication – which includes critical colour assessment of

prints, hardcopy proofs and monitor softcopy proofs – is only possible when these

criteria are adhered to at all stages of the production process through use of

appropriate standard light booths and proof lights.

Source

This article was produced in cooperation with JUST Normlicht GmbH.

Further information and advice: www.just-normlicht.de