D50 is the standard lighting condition of the printing industry. It has a degree of whiteness of 5,000 Kelvin, which is the colour that glowing metal at 5,000 Kelvin would cast.
With the ISO 3664: 2009, the D50 standard lighting condition has undergone a change. It now contains a higher UV spectrum. Since this change had not been clearly communicated to all commercial printers and prepress businesses, even today there are many D50 lights with old neon pipes, causing confusion in matching colour. In one printing studio, two D50 light units might be next to each other, that have different UV components and thus, for example, the optical brighteners in modern uncoated papers are visually completely different.
D65 is standardized viewing condition with 6500 K color temperature. It is the default setting for most monitors and is mainly used in color matching etc. for websites, so in media that are considered primarily to be viewed on the monitor.
In the printing industry, the standard light is D50 according to ISO 3664: 2009 standard, a warmer light than D65 with 5000 Kelvin color temperature, which is also used for color matching on the press and in the evaluation of proofs.
The GTI GmbH is beside Just Normlicht a renowned manufacturer of standard light tubes and standardized light consoles and colour cabins. GTI offers numerous systems for colour assessment, but is- other than Just – opposed the use of LED, and therefore offers only special neon-based solutions. LEDs in the standard light industry are according to GTI economically and qualitatively no real alternative to the renown and tested tubes.
The Just Normlicht GmbH is the most famous manufacturer of standard lighting solutions in the printing sector. The company Just from the Swabian Weilheim / Teck sells alongside the classic D50 and D65 standard light tubes and various proof lights, stations and light booths, where prints can be checked under standardized lighting. In recent years, the LED technology has been introduced, so that now several devices with LED technology are offered. Another well-known company is GTI; Standard light tubes are also manufactured by OSRAM and other manufacturers.
Kelvin is an absolute temperature unit, which is used in science.
The color temperature is in Kelvin of a light source, a monitor or an image corresponds to the temperature of a perfectly black object, that would glow at this temperature.
The word “degrees” is incidentally not used in conjunction with Kelvin. A temperature of 5000 Kelvin is not referred to as “5000 degrees Kelvin,” but only over 5000 Kelvin or “K 5000”.
A standardized light is called a defined light condition under which the viewer can view and assess prints or objects uniformly. The most important standard illuminants D50 are in accordance with ISO 3664:2009 for printmaker and for colour matching in prepress and press (colour temperature: 5,000 kelvin) and D65 (colour temperature: 6500 K) for internet graphic designer. D65 is the default setting for most monitors.
Other important types of light are TL84, the standard neon light (colour temperature: 4,100 kelvin), which dominates factories and supermarkets, and A – incandescent light (light bulb) with a colour temperature of 2,700 Kelvin.