ISO 3664 - International Standard for artificial light

It has long been accepted that there is a need for an international standard for artificial light sources used in the assessment of colour. Daylight has a broad spectrum but suffers from being variable in both quantity and quality, and most artificial light sources require filtering.

CIE discussions led to an agreement to specify two light distributions one CIE Illuminant D.6500 and the other Illuminant D.5000/5300. In Britain these distributions have been incorporated into BS950 Part 1 (daylight/TLD95 and C95 PLL Compact Tube) and BS950 Part 2 (northlight/TLD96), respectively. Philips are the first company to produce single light sources having light distributions designed to meet the requirements of both parts of this standard, and the new EU standard ISO 3664.

Use of an agreed light source eliminates possible differences of opinion between supplier and client and inconsistent results between different branches of an organisation. It also enables critical assessment of colour to be done at all times, even outside daylight hours when previously this was impossible. It is recommended that clients adopt the same light source for use at all times of the day or night