ASTM International

Standard Practice for Specifying Color by the Natural Colour System (NCS)
 N E2970

Annotation

The Natural Colour System (NCS) (see 1.7) provides a color notation system that can be used to communicate color. This practice introduces the Natural Colour System, its terminology, and conversion to and from CIE tristimulus values.

The system described in this standard includes color percepts that appear to belong to the surface of a material, provided the surface is not perceived to be fluorescent or to exhibit directional color effects.

The system does not include colors that appear to belong to translucent or luminescent objects (so-called volume colors and luminous colors), nor does it include other visual properties of the surface layer, such as gloss and texture. An NCS notation does not describe the physical or chemical properties of an object.

This practice also specifies the conditions for visual or instrumental determination of the NCS notation of a color sample, defines the relationships between psychometrically determined NCS notations and the corresponding CIE color coordinates which are to be used in this context.

For the accuracy requirements associated with NCS standards and NCS color samples, the user is referred to Swedish Standard SS 19104. The colored illustrations in this standard shall not be used as standard color samples in any way. Color illustrations that are shown on screen or in printouts may be significantly different than the original NCS color samples with the same NCS Notation due to limited color reproduction capabilities in screens and printers.

The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.