Standardized light refers to defined lighting conditions under which viewers can uniformly view and evaluate prints or objects, i.e. a type of light whose spectral radiation distribution is standardised and normalised. Since the perception of colours depends heavily on the type of lighting, only standard light enables reliable and repeatable colour assessment. This standardisation is crucial for harmonising colour specifications and colour samples independently of the viewer and the viewing location.
The standardized light types are defined by the International Commission on Illumination (CIE). These are not real light sources, but mathematically defined spectral curves that simulate certain lighting conditions. In practice, real light sources can only approximate these curves.
The most important standardized light types are divided according to their area of application:
- D series (daylight): The standardized light types in the D series (D stands for ‘daylight’) simulate daylight with different colour temperatures.
- D50 (5000 Kelvin) corresponds to neutral daylight and is the binding standard for the graphics industry (printing and pre-press). It is used to calibrate and sample printed products and screens, i.e. to visually check colour accuracy.
- D65 (6500 Kelvin) represents average daylight under cloudy skies in Western and Northern Europe. D65 is used in many industrial sectors for visual colour assessment and screen calibration.
- Standard illuminant A (2856 K): This standard illuminant was defined in 1931 and simulates the light of a conventional incandescent lamp in the home. It is used to evaluate objects under warm light conditions.
- The CIE has defined various standardized light types in the F series – F1 to F12. These represent the light from fluorescent tubes with different colour rendering indices and different colour temperatures.
The most important standardized light types in the printing industry are D50 according to ISO 3664:2009 for graphic designers and for colour matching on the printing press (colour temperature: 5,000 Kelvin) and D65 (colour temperature: 6,500 Kelvin) for web designers. D65 is the default setting for most monitors.
Metamerism
The importance of standardized lighting becomes particularly clear when considering the phenomenon of metamerism. Metameric colours are two colour samples that appear identical under a certain light but differ under different lighting conditions. Standardized lighting ensures that colour matching carried out under standardized conditions is not distorted by different lighting conditions. Many standardized lighting booths, such as those from JUST, GTI or PANTONE, in which colour matching takes place, also offer the option of switching between different types of standardized lighting in order to detect metameric effects.
Manufacturer
Major manufacturers of standardized light sources, standardized light tubes (the sale of traditional neon tubes has been prohibited in the EU since 2023) and standardized light booths in Germany are:
- Just Normlicht and GTI Normlicht for standardized series solutions
- Lacunasolutions in Bavaria for customised solutions