ASTM E2970-22

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

SIGNIFICANCE AND USE
5.1 The Natural Colour System is a color notation system that builds on how a human being sees color. An NCS notation represents a specific color percept and describes the color as perceived; it is not dependent on limitations caused by pigments, light rays or nerve signals that have given rise to this perception. The NCS system is used internationally in such fields as architecture, corporate identity, cosmetics, education, fashion and textile forecasting and production, interior design and product design. The Natural Colour System describes colors exactly as they are seen. Any of the millions of colors that exist can be defined within the NCS system and given a precise notation. When the NCS system is known, it is possible to judge the attributes of a color by its NCS notation; for example, how much blackness, how much chromaticness, and what hue? This helps to communicate and check specifications and to identify colors. Some examples of the use of NCS are: (1) Architects and designers use the NCS color samples to select colors for all kind of products and materials; (2) They also use the NCS notation to analyze the colors in use in a particular area and to document their specifications; (3) Companies use the NCS color samples as the production standards for their products; (4) Paint manufacturers and other industries use the NCS notation and the NCS color samples to visualize the color of their products to customers, and (5) Companies use the NCS samples as high quality color standards in corporate identity programs and manuals.
SCOPE
1.1 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.  
1.2 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.  
1.3 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.  
1.4 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.  
1.5 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.  
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.7 Acknowledgement—NCS, Natural Colour System is a trademark of the NCS Colour AB Stockholm, Sweden and is protected by copyright (www.ncscolour.com). All rights reserved. Original NCS color samples are only available form NCS Colour AB or any authorized NCS distributor. Commercial use of the NCS System requires a license from NCS Colour AB.  
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.9 This international standard was developed in accordance with internation...

General Information

• Status: Published
• Publication Date: 30-Sep-2022
• ICS: 17.180.20 - Colours and measurement of light
• Technical Committee: E12 - Color and Appearance
• Drafting Committee: E12.07 - Color Order Systems

Relations

• Refers: ASTM E1164-23 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Nov-2023
• Refers: ASTM E308-17 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-May-2017
• Refers: ASTM E308-15 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Apr-2015
• Refers: ASTM E284-13b - Standard Terminology of Appearance
• Effective Date: 01-Nov-2013
• Refers: ASTM E284-13a - Standard Terminology of Appearance
• Effective Date: 01-Jun-2013
• Refers: ASTM E284-13 - Standard Terminology of Appearance
• Effective Date: 01-Jan-2013
• Refers: ASTM E284-12 - Standard Terminology of Appearance
• Effective Date: 01-Jul-2012
• Refers: ASTM E1164-12 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jul-2012
• Refers: ASTM E1164-12e1 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jul-2012
• Refers: ASTM E308-12 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Jul-2012
• Refers: ASTM E284-09a - Standard Terminology of Appearance
• Effective Date: 01-Jun-2009
• Refers: ASTM E1164-09a - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jun-2009
• Refers: ASTM E1164-09 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 15-Feb-2009
• Refers: ASTM E284-09 - Standard Terminology of Appearance
• Effective Date: 01-Jan-2009
• Refers: ASTM E308-08 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Dec-2008

Overview

ASTM E2970-22: Standard Practice for Specifying Color by the Natural Colour System (NCS) defines internationally recognized procedures for specifying and communicating color based on human visual perception. This standard introduces the Natural Colour System (NCS), a color notation method that describes how colors appear to an observer, independent of the physical or chemical properties of materials. Used widely in architecture, design, manufacturing, and other industries, NCS provides a standardized framework to define and reproduce millions of colors, ensuring precision and consistency across applications.

Key Topics

• Perceptual Color Specification: The NCS system is based on how humans perceive color. Each NCS notation describes a perceived color, not constrained by material limitations or the underlying colorants.

• Color Components and Notation:

  • Six elementary (pure) colors: white (W), black (S), yellow (Y), red (R), blue (B), and green (G).
  • All other colors are specified in terms of their resemblance to these elementary colors, using elementary attributes such as whiteness, blackness, chromaticness, and hue.
  • NCS notations are alphanumeric codes that define the blackness, chromaticness, and hue of a color, enabling precise communication.

• Visual and Instrumental Methods:

  • Visual method: Direct comparison of specimens to standardized NCS color samples under controlled lighting and environmental conditions.
  • Instrumental method: Conversion between NCS notations and CIE tristimulus values (CIE Lab*, XYZ), supporting digital color management and automation.

• Scope Limitations:

  • The standard applies to opaque, non-fluorescent surfaces. It does not cover translucent or luminescent colors, or surface texture and gloss.
  • NCS color samples must be physical reference materials, as screen or print reproductions may not accurately reflect true colors.

Applications

The Natural Colour System, as defined in ASTM E2970-22, is widely adopted for:

• Architecture & Interior Design: Specification and harmonization of colors in buildings, interiors, and public spaces. NCS enables designers to match, compare, and document color choices with precision.
• Corporate Identity & Product Design: Ensures consistent brand colors and product appearances across manufacturing sites, packaging, marketing, and corporate communications.
• Textile & Fashion Industry: Used for forecasting, product development, and quality control, ensuring color consistency from concept to consumer.
• Paints & Coatings Manufacturing: Paint producers use NCS codes to match customer requirements and to communicate colors to clients and within production.
• Education & Research: Facilitates teaching and research in color science, offering a standardized terminology for color communication.
• Cosmetics: Used to match and specify product shades precisely across batches and product lines.

Related Standards

The use of ASTM E2970-22 is often complemented by the following standards and references:

• ASTM E284: Terminology of Appearance
• ASTM E308: Practice for Computing the Colors of Objects Using the CIE System
• ASTM E1164: Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• SS 19100: Swedish Standards for Colour Notation System
• SS 19102: NCS Colour Atlas
• SS 19104: Measurement conditions and tolerances for NCS color samples
• CIE 15:2004 No.15: Colorimetry

These standards enable conversion between NCS and other colorimetric systems and ensure reliable assessment, instrument calibration, and documentation.

Practical Value

Adopting ASTM E2970-22 streamlines color specification and communication throughout global supply chains, design processes, and across diverse industries. By providing a shared language based on human color perception, the Natural Colour System facilitates accurate, reliable color matching, reduces errors, and supports compliance with international best practices for color management.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2970 − 22
Standard Practice for
Specifying Color by the Natural Colour System (NCS)
This standard is issued under the fixed designation E2970; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope served. Original NCS color samples are only available form
NCS Colour AB or any authorized NCS distributor. Commer-
1.1 The Natural Colour System (NCS) (see 1.7) provides a
cial use of the NCS System requires a license from NCS Colour
color notation system that can be used to communicate color.
AB.
This practice introduces the Natural Colour System, its
terminology, and conversion to and from CIE tristimulus 1.8 This standard does not purport to address all of the
values. safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
1.2 The system described in this standard includes color
priate safety, health, and environmental practices and deter-
percepts that appear to belong to the surface of a material,
mine the applicability of regulatory limitations prior to use.
provided the surface is not perceived to be fluorescent or to
1.9 This international standard was developed in accor-
exhibit directional color effects.
dance with internationally recognized principles on standard-
1.3 Thesystemdoesnotincludecolorsthatappeartobelong
ization established in the Decision on Principles for the
to translucent or luminescent objects (so-called volume colors
Development of International Standards, Guides and Recom-
and luminous colors), nor does it include other visual proper-
mendations issued by the World Trade Organization Technical
ties of the surface layer, such as gloss and texture. An NCS
Barriers to Trade (TBT) Committee.
notation does not describe the physical or chemical properties
of an object.
2. Referenced Documents
1.4 This practice also specifies the conditions for visual or
2.1 ASTM Standards:
instrumental determination of the NCS notation of a color
E284 Terminology of Appearance
sample, defines the relationships between psychometrically
E308 PracticeforComputingtheColorsofObjectsbyUsing
determined NCS notations and the corresponding CIE color
the CIE System
coordinates which are to be used in this context.
E1164 PracticeforObtainingSpectrometricDataforObject-
1.5 For the accuracy requirements associated with NCS
Color Evaluation
standards and NCS color samples, the user is referred to
2.2 Swedish Standards:
Swedish Standard SS 19104. The colored illustrations in this
SS 19100 Colour Notation system
standard shall not be used as standard color samples in any
SS 19102 NCS Colour Atlas
way.Colorillustrationsthatareshownonscreenorinprintouts
SS 19104 NCS colour samples — Observation and measure-
may be significantly different than the original NCS color
ment conditions and tolerances
samples with the same NCS Notation due to limited color
2.3 Other Documents:
reproduction capabilities in screens and printers.
CIE No. 15 Colorimetry
1.6 The values stated in SI units are to be regarded as
2.4 ASTM Adjuncts:
standard. No other units of measurement are included in this
Spreadsheet for NCS Notations and CIE Coordinates
standard.
1.7 Acknowledgement—NCS, Natural Colour System is a
trademark of the NCS Colour AB Stockholm, Sweden and is
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
protected by copyright (www.ncscolour.com). All rights re-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
1 3
This practice is under the jurisdiction of ASTM Committee E12 on Color and Available from Swedish Institute for Standards, Box 45443, SE-104 31
Appearance and is the direct responsibility of Subcommittee E12.07 on Color Order Stockholm, Sweden, www.sis.se.
Systems. Available from U.S. National Committee of the CIE (International Commission
Current edition approved Oct. 1, 2022. Published November 2022. Originally on Illumination) or CIE Webshop http://www.techstreet.com/cie.
approved in 2014. Last previous edition approved in 2015 as E2970 – 15. DOI: Available from ASTM International Headquarters. Order Adjunct No.
10.1520/E2970-22. ADJE2970S-EA. Original adjunct produced in 2014.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2970 − 22
3. Terminology 3.2.5.1 Discussion—The NCS hue is a perceptual quantity
derived from the chromatic elementary attributes. The NCS
3.1 Terms and definitions in Terminology E284 are appli-
hue is expressed by a number between 0 and 100 as the
cable to this practice.
proportion of one chromatic elementary attribute in the sum of
3.2 Definitions of Terms Specific to This Standard:
the (at most two) chromatic elementary attributes, that is, the
3.2.1 elementary color, n—oneofthesixcolorperceptseach
NCS chromaticness. The “one” always refers to the chromatic
of which can be described only by reference to itself.
elementary attribute which is placed last in Eq 2. In formulae
3.2.1.1 Discussion—The elementary colors, which are des-
(but not in NCS notations), the hue is denoted by the symbolΦ
ignated with uppercase letters, are as follows: white (W), black
togetherwithasuffix.Thesuffixconsistsoftheitaliclowercase
(S), yellow (Y), red (R), blue (B), green (G). All other colors
letters for the pair of chromatic elementary attributes in
can be described in terms of their resemblance to these six.
question, that is, yr, rb, bg,or gy. It follows that:
Whiteandblackareachromaticelementarycolors.Yellow,red,
Φ 5 100 r⁄ y 1 r 5 100 r ⁄ c (4)
~ !
yr
blue and green are chromatic elementary colors.
Φ 5 100 b⁄ r 1 b 5 100 b⁄c (5)
~ !
rb
3.2.2 elementary attribute, n—the degree of resemblance of
Φ 5 100 g⁄ b 1 g 5 100 g⁄c (6)
~ !
a color to an elementary color. bg
3.2.2.1 Discussion—The elementary attributes, which are
Φ 5 100 y⁄ ~g 1 y! 5 100 y⁄c (7)
gy
designated by italic lowercase letters, are: whiteness (w), Eq 4-7 can also be used in reverse to calculate the chromatic
blackness (s), yellowness (y), redness (r), blueness (b), and
elementary properties when the NCS chromaticness and
greenness (g). Whitenessand blacknessareachromaticelemen- NCS hue are known.
tary attributes. Yellowness, redness, blueness and greenness are
3.2.6 NCS nuance, n—the composition of whiteness, black-
chromatic elementary attributes. All are perceptual quantities,
ness and chromaticness in a color, regardless of the hue.
which are expressed by a number between 0 and 100. For any
3.2.6.1 Discussion—The NCS nuance is expressed by a pair
arbitrary color the following apply:
of numbers which represent the blackness and chromaticness
(a) the color cannot simultaneously possess yellowness and
of the color. The whiteness is excluded, since it is given by
blueness,
Eq 3. The NCS nuance is a perceptual quantity derived from
(b) the color cannot simultaneously possess redness and
the elementary attributes. It has an unambiguous NCS notation
greenness,
throughthefirstfourfiguresinthealpha–numericalbasiccode.
(c) the sum of its elementary attributes is 100.
It follows that a color can have at most four elementary 3.2.7 NCS saturation, n—the relation between the chromat-
attributes in one of the following combinations:
icness of a color and its whiteness, regardless of the hue.
3.2.7.1 Discussion—NCS saturation is a perceptual quantity
w1 s1 c 1 c 5 100 (1)
1 2
where c and c are adjoining elementary chromatic
derived from the elementary attributes. The NCS saturation is
1 2
colors, such as y and r, r and b, b and g,or g and y.
expressed by a number between 0 and 1 for the ratio of the
chromaticness (c) of the color to the sum of its whiteness (w)
3.2.3 full chromatic color, n—a color that lacks the elemen-
and chromaticness (c). The NCS saturation is designated by an
tary attributes of whiteness and blackness.
italic lowercase m. It follows that:
3.2.3.1 Discussion—A full chromatic color, regardless of
hue,isdesignatedbyanuppercaseletter, C.Thefourchromatic
m 5 c ⁄ ~w 1 c! (8)
elementary colorsY, R, B and G are also full chromatic colors.
where w+c is equal to 100 -s.
3.2.4 NCS chromaticness, n—the degree of resemblance of
3.2.8 NCS lightness, n—a characteristic of a color such that
a color to the full chromatic color of the same hue.
it appears to have more of the elementary color black or white
3.2.4.1 Discussion—NCS chromaticness is a perceptual
than another color.
quantity derived from the chromatic elementary attributes. The
3.2.8.1 Discussion—NCS lightness is a perceptual quantity,
NCS chromaticness is expressed by a number between 0 and
designated by a lowercase v, the value of which varies between
100 for the sum of the (at most two) chromatic elementary
zero (0) for the elementary color black (S) and one (1) for the
attributes, and it is designated by an italic lowercase c. It
elementarycolorwhite(W).Forachromatic(puregray)colors
follows that:
including the elementary colors white (W) and black (S), for
c 5 c 1 c (2)
1 2
which c=0, v is defined as:
where c and c are adjoining elementary chromatic
1 2
colors, such as y and r, r and b, b and g,or g and y.
v 5 100 2 s ⁄ 100 (9)
~ !
The NCS lightness of any arbitrary color specimen is deter-
Eq 1 and Eq 2 can then be written:
mined by comparison edge-to-edge with a reference scale of
achromatic color samples (c = 0). The color specimen is as-
w1 s1c 5 100 (3)
signed the same lightness value as that of the reference
For achromatic (pure gray) colors including the elementary
sample for which the border between specimen and refer-
colors white and black, c = 0 and w + s = 100. For maximal
ence is perceived to be least distinct.
colors, w + s = 0 and c = 100.
3.2.5 NCS hue, n—the relation between the (at most two) 3.2.9 luminance factor, Y, n—ratio of the luminance of a
chromatic elementary attributes of a color, regardless of the specimen to that of a perfect diffuser, when illuminated and
whiteness and blackness of the color. viewed under specified geometric conditions.
E2970 − 22
3.2.9.1 Discussion—IntheCIE1931system,thisquantityis followed by two capitals enclosing two figures (00–99). The
tristimulus value Y. capitals show the relevant chromatic elementary colors. See
Fig. 1. In practice a variation of this basic code with different
4. Summary of Practice
or fewer characters is often used.
6.1.2 A chromatic color with c < 100 and with two chro-
4.1 Visual Method—Observers should have normal color
matic elementary attributes is designated by the basic code.
vision. Specimens should be viewed on an essentially nonse-
Example: 5535-R20B designates a color with a blackness of
lective gray background of approximately 56 % luminance
55, a chromaticness of 35, and a hue of (80 %) red and 20 %
factor with natural or artificial daylight of approximately
blue. The parentheses are added here to mark that this figure is
1000 lux. The test specimen should be compared edge-to-edge
not shown in the notation.
to the colors in the NCS Original Collection (for example, in
6.1.3 A chromatic color with c < 100 and with only one
SS 019102 NCS Colour Atlas). The size of the specimen
chromatic elementary attribute is designated by a code which
should be at least 40 mm by 50 mm with an immediate white
lacks the last three figures of the basic code. Example: 5535-R.
surround of 85 % luminance factor. The specimen and color
6.1.4 An achromatic (pure gray) color, but not one of the
chip should be perpendicular to the observer with the illumi-
elementary colors white and black is, however, designated by
nation at an angle of approximately 45°.
a code with a capital N instead of the last four figures of the
4.2 Instrumental Method—CIE 1931 tristimulus values for
basic code. The capital N means “neutral.” Two examples:
standard illuminant D65 and the CIE 1931 standard colorimet-
2500-N and 7000-N.
ric observer are obtained from spectrophotometric or colori-
6.1.5 A full chromatic color, but not one of the elementary
metric measurement. See Practices E308 and E1164. Compu-
colors yellow, red, blue or green is, however, designated by a
tationofNCSnotationvaluescanbeachievedbyfollowingthe
codewiththecapitalCinsteadofthefourfirstcharactersofthe
directions in Annex A1 and using the tables in the adjunct.
basic code. Example: C-R80B.
6.1.6 The six elementary colors are designated by the
5. Significance and Use
capitals W, S, Y, R, B and G. See Fig. 2.
5.1 The Natural Colour System is a color notation system
6.2 NCS Color Triangle—An NCS color triangle is an
that builds on how a human being sees color.An NCS notation
equilateral triangle within which each point unambiguously
represents a specific color percept and describes the color as
represents a color with a certain NCS nuance, regardless of the
perceived; it is not dependent on limitations caused by
hue of the color. See Fig. 3.
pigments, light rays or nerve signals that have given rise to this
6.2.1 Thethreeperpendiculardistancesfromthesidesofthe
perception. The NCS system is used internationally in such
triangle to an arbitrary point within the triangle are designated
fields as architecture, corporate identity, cosmetics, education,
w, s and c and the height of the triangle is set equal to 100, see
fashion and textile forecasting and production, interior design
Fig. 3. According to the geometry of equilateral triangles, it
and product design. The Natural Colour System describes
follows that:
colors exactly as they are seen. Any of the millions of colors
that exist can be defined within the NCS system and given a w1 s1 c 5 100 (10)
that is, the same as Eq 3.
precise notation.When the NCS system is known, it is possible
This means that a given point in the color triangle unam-
to judge the attributes of a color by its NCS notation; for
biguously represents all colors with a certain composition of
example, how much blackness, how much chromaticness, and
whiteness (w), blackness (s) and NCS chromaticness (c), that
what hue? This helps to communicate and check specifications
is, all colors with the same NCS nuance. To determine the
and to identify colors. Some examples of the use of NCS are:
location of the point and thereby the NCS nuance, it is suffi-
(1) Architects and designers use the NCS color samples to
cient to indicate the numerical values of s and c, since the
select colors for all kind of products and materials; (2) They sum of w, s and c is always 100.
also use the NCS notation to analyze the colors in use in a
particular area and to document their specifications; (3) Com-
panies use the NCS color samples as the production standards
for their products; (4) Paint manufacturers and other industries
use the NCS notation and the NCS color samples to visualize
thecoloroftheirproductstocustomers,and(5)Companiesuse
the NCS samples as high quality color standards in corporate
identity programs and manuals.
6. Specifying Color with a NCS Notation
For example in the NCS notation 1050-Y90R, 1050 describes the nuance, that
6.1 NCS Notation—An NCS notation consists of an alpha- is, the degree of resemblance to whiteness (40 %) and blackness which is 10 %
and to the maximum chromaticness which is 50 %. The whiteness is not shown but
numerical code, the letters and figures of which describe the
is the remaining 40 % (100-10-50=40). The hue Y90R describes the degree of
appearance of the designated color.
resemblance between Yellow and Red (Y and R). Y90R describes a red color with
(10 %) yellowness. In the NCS notation this is written as yellow with 90 % redness.
6.1.1 The Alpha-numerical Code—The alpha-numerical ba-
The letter S preceding the complete NCS notation (S 1050-Y90R) denotes an NCS
sic code for an NCS notation has nine characters, which in turn
notation that is available as standardized physical color samples in SS 19102 NCS
indicate the blackness and NCS chromaticness, each with two
Colour Atlas.
figures (00–99), and thereafter the NCS hue by a hyphen FIG. 1 NCS Notation
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2970 − 15 E2970 − 22
Standard Practice for
Specifying Color by the Natural Colour System (NCS)
This standard is issued under the fixed designation E2970; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 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.
1.2 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.
1.3 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.
1.4 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.
1.5 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.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 Acknowledgement—NCS, Natural Colour System is a trademark of the NCS Colour AB Stockholm, Sweden and is protected
by copyright (www.ncscolour.com). All rights reserved. Original NCS color samples are only available form NCS Colour AB or
any authorized NCS distributor. Commercial use of the NCS System requires a license from NCS Colour AB.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.9 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.07 on Color Order
Systems.
Current edition approved Dec. 1, 2015Oct. 1, 2022. Published December 2015November 2022. Originally approved in 2014. Last previous edition approved in 20142015
as E2970 – 14.15. DOI: 10.1520/E2970-15.10.1520/E2970-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2970 − 22
2. Referenced Documents
2.1 ASTM Standards:
E284 Terminology of Appearance
E308 Practice for Computing the Colors of Objects by Using the CIE System
E1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation
2.2 Swedish Standards:
SS 19100 Colour Notation system
SS 19102:200419102 NCS Colour Atlas
SS 19104 NCS colour samples — Observation and measurement conditions and tolerances
2.3 Other Documents:
CIE 15:2004No. 15 Colorimetry
2.4 ASTM Adjuncts:
Spreadsheet for NCS Notations and CIE Coordinates
3. Terminology
3.1 Terms and definitions in Terminology E284 are applicable to this practice.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 elementary color, n—one of the six color percepts each of which can be described only by reference to itself.
3.2.1.1 Discussion—
The elementary colors, which are designated with uppercase letters, are as follows: white (W), black (S), yellow (Y), red (R), blue
(B), green (G). All other colors can be described in terms of their resemblance to these six. White and black are achromatic
elementary colors. Yellow, red, blue and green are chromatic elementary colors.
3.2.2 elementary attribute, n—the degree of resemblance of a color to an elementary color.
3.2.2.1 Discussion—
The elementary attributes, which are designated by italic lowercase letters, are: whiteness (w), blackness (s), yellowness (y),
redness (r), blueness (b), and greenness (g).Whiteness and blackness are achromatic elementary attributes. Yellowness, redness,
blueness and greenness are chromatic elementary attributes. All are perceptual quantities, which are expressed by a number
between 0 and 100. For any arbitrary color the following apply:
(a) the color cannot simultaneously possess yellowness and blueness,
(b) the color cannot simultaneously possess redness and greenness,
(c) the sum of its elementary attributes is 100.
It follows that a color can have at most four elementary attributes in one of the following combinations:
w1 s1 c 1 c 5 100 (1)
1 2
where c and c are adjoining elementary chromatic colors, such as y and r,r and b,b and g, or g and y.
1 2
3.2.3 full chromatic color, n—a color that lacks the elementary attributes of whiteness and blackness.
3.2.3.1 Discussion—
A full chromatic color, regardless of hue, is designated by an uppercase letter, C. The four chromatic elementary colors Y, R, B
and G are also full chromatic colors.
3.2.4 NCS chromaticness, n—the degree of resemblance of a color to the full chromatic color of the same hue.
3.2.4.1 Discussion—
NCS chromaticness is a perceptual quantity derived from the chromatic elementary attributes. The NCS chromaticness is expressed
by a number between 0 and 100 for the sum of the (at most two) chromatic elementary attributes, and it is designated by an italic
lowercase c. It follows that:
c 5 c 1 c (2)
1 2
where c and c are adjoining elementary chromatic colors, such as y and r,r and b,b and g, or g and y.
1 2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Swedish Standards Institute, SIS Förlag AB, SE-118 80Institute for Standards, Box 45443, SE-104 31 Stockholm, Sweden, www.sis.se.
Available from U.S. National Committee of the CIE (International Commission on Illumination) or CIE Webshop http://www.techstreet.com/cie.
Available from ASTM International Headquarters. Order Adjunct No. ADJE2970S-EA. Original adjunct produced in 2014.
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Eq 1 and Eq 2 can then be written:
w1 s1c 5 100 (3)
For achromatic (pure gray) colors including the elementary colors white and black, c = 0 and w + s = 100. For maximal
colors, w + s = 0 and c = 100.
3.2.5 NCS hue, n—the relation between the (at most two) chromatic elementary attributes of a color, regardless of the whiteness
and blackness of the color.
3.2.5.1 Discussion—
The NCS hue is a perceptual quantity derived from the chromatic elementary attributes. The NCS hue is expressed by a number
between 0 and 100 as the proportion of one chromatic elementary attribute in the sum of the (at most two) chromatic elementary
attributes, that is, the NCS chromaticness. The “one” always refers to the chromatic elementary attribute which is placed last in
Eq 2. In formulae (but not in NCS notations), the hue is denoted by the symbol Φ together with a suffix. The suffix consists of
the italic lowercase letters for the pair of chromatic elementary attributes in question, that is, yr,rb,bg, or gy. It follows that:
Φ 5 100 r⁄ y 1 r 5 100 r ⁄ c (4)
~ !
yr
Φ 5 100 b⁄ r 1 b 5 100 b⁄c (5)
~ !
rb
Φ 5 100 g⁄ b 1 g 5 100 g⁄c (6)
~ !
bg
Φ 5 100 y⁄ g 1 y 5 100 y⁄c (7)
~ !
gy
Eq 4-7 can also be used in reverse to calculate the chromatic elementary properties when the NCS chromaticness and NCS
hue are known.
3.2.6 NCS nuance, n—the composition of whiteness, blackness and chromaticness in a color, regardless of the hue.
3.2.6.1 Discussion—
The NCS nuance is expressed by a pair of numbers which represent the blackness and chromaticness of the color. The whiteness
is excluded, since it is given by
Eq 3. The NCS nuance is a perceptual quantity derived from the elementary attributes. It has an unambiguous NCS notation
through the first four figures in the alpha–numerical basic code.
3.2.7 NCS saturation, n—the relation between the chromaticness of a color and its whiteness, regardless of the hue.
3.2.7.1 Discussion—
NCS saturation is a perceptual quantity derived from the elementary attributes. The NCS saturation is expressed by a number
between 0 and 1 for the ratio of the chromaticness (c) of the color to the sum of its whiteness (w) and chromaticness (c). The NCS
saturation is designated by an italic lowercase m. It follows that:
m 5 c ⁄ w 1 c (8)
~ !
where w + c is equal to 100 -s.
3.2.8 NCS lightness, n—a characteristic of a color such that it appears to have more of the elementary color black or white than
another color.
3.2.8.1 Discussion—
NCS lightness is a perceptual quantity, designated by a lowercase v, the value of which varies between zero (0) for the elementary
color black (S) and one (1) for the elementary color white (W) . For achromatic (pure gray) colors including the elementary colors
white (W) and black (S), for which c = 0, v is defined as:
v 5 100 2 s ⁄ 100 (9)
~ !
The NCS lightness of any arbitrary color specimen is determined by comparison edge-to-edge with a reference scale of achro-
matic color samples (c = 0). The color specimen is assigned the same lightness value as that of the reference sample for
which the border between specimen and reference is perceived to be least distinct.
3.2.9 luminance factor, Y, n—ratio of the luminance of a specimen to that of a perfect diffuser, when illuminated and viewed under
specified geometric conditions.
3.2.9.1 Discussion—
In the CIE 1931 system, this quantity is tristimulus value Y.
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4. Summary of Practice
4.1 Visual Method—Observers should have normal color vision. Specimens should be viewed on an essentially nonselective gray
background of approximately 56 % luminance factor with natural or artificial daylight of approximately 1000 lux. 1000 lux. The
test specimen should be compared edge-to-edge to the colors in the NCS 1950 Original Collection (for example, in
SS 019102:2004 SS 019102 NCS Colour Atlas). The size of the specimen should be at least 4040 mm by 50 mm with an immediate
white surround of 85 % luminance factor. The specimen and color chip should be perpendicular to the observer with the
illumination at an angle of approximately 45°.
4.2 Instrumental Method—CIE 1931 tristimulus values for standard illuminant D65 and the CIE 1931 standard colorimetric
observer are obtained from spectrophotometric or colorimetric measurement. See Practices E308 and E1164. Computation of NCS
notation values can be achieved by following the directions in Annex A1 and using the tables in the adjunct.
5. Significance and Use
5.1 The Natural Colour System is a color notation system that builds on how a human being sees color. An NCS notation
represents a specific color percept and describes the color as perceived; it is not dependent on limitations caused by pigments, light
rays or nerve signals that have given rise to this perception. The NCS system is used internationally in such fields as architecture,
corporate identity, cosmetics, education, fashion and textile forecasting and production, interior design and product design. The
Natural Colour System describes colors exactly as they are seen. Any of the millions of colors that exist can be defined within the
NCS system and given a precise notation. When the NCS system is known, it is possible to judge the attributes of a color by its
NCS notation; for example, how much blackness, how much chromaticness, and what hue? This helps to communicate and check
specifications and to identify colors. Some examples of the use of NCS are: (1) Architects and designers use the NCS color samples
to select colors for all kind of products and materials; (2) They also use the NCS notation to analyze the colors in use in a particular
area and to document their specifications; (3) Companies use the NCS color samples as the production standards for their products;
(4) Paint manufacturers and other industries use the NCS notation and the NCS color samples to visualize the color of their
products to customers, and (5) Companies use the NCS samples as high quality color standards in corporate identity programs and
manuals.
6. Specifying Color with a NCS Notation
6.1 NCS Notation—An NCS notation consists of an alpha-numerical code, the letters and figures of which describe the appearance
of the designated color.
6.1.1 The Alpha-numerical Code—The alpha-numerical basic code for an NCS notation has nine characters, which in turn indicate
the blackness and NCS chromaticness, each with two figures (00–99), and thereafter the NCS hue by a hyphen followed by two
capitals enclosing two figures (00–99). The capitals show the relevant chromatic elementary colors. See Fig. 1. In practice a
variation of this basic code with different or fewer characters is often used.
6.1.2 A chromatic color with c <100 < 100 and with two chromatic elementary attributes is designated by the basic code. Example:
5535-R20B designates a color with a blackness of 55, a chromaticness of 35, and a hue of (80 %) red and 20 % blue. The
parentheses are added here to mark that this figure is not shown in the notation.
6.1.3 A chromatic color with c <100 < 100 and with only one chromatic elementary attribute is designated by a code which lacks
the last three figures of the basic code. Example: 5535-R.
For example in the NCS notation 1050-Y90R, 1050 describes the nuance, that is, the degree of resemblance to whiteness (40 %) and blackness which is 10 % and to
the maximum chromaticness which is 50 %. The whiteness is not shown but is the remaining 40 % (100-10-50=40). The hue Y90R describes the degree of resemblance
between Yellow and Red (Y and R). Y90R describes a red color with (10 %) yellowness. In the NCS notation this is written as yellow with 90 % redness. (TheThe letter
S preceding the complete NCS notation (S 1050-Y90R) denotes an NCS notation that is available as standardized physical color samples in SS 19102:200419102 NCS
Colour Atlas.
FIG. 1 NCS Notation
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6.1.4 An achromatic (pure gray) color, but not one of the elementary colors white and black is, however, designated by a code
with a capital N instead of the last four figures of the basic code. The capital N means “neutral.” Two examples: 2500-N and
7000-N.
6.1.5 A full chromatic color, but not one of the elementary colors yellow, red, blue or green is, however, designated by a code with
the capital C instead of the four first characters of the basic code. Example: C-R80B.
6.1.6 The six elementary colors are designated by the capitals W, S, Y, R, B and G. See Fig. 2.
6.2 NCS Color Triangle—An NCS color triangle is an equilateral triangle within which each point unambiguously represents a
color with a certain NCS nuance, regardless of the hue of the color. See Fig. 3.
6.2.1 The three perpendicular distances from the sides of the triangle to an arbitrary point within the triangle are designated w,
s and c and the height of the triangle is set equal to 100, see Fig. 3. According to the geometry of equilateral triangles, it follows
that:
w1 s1 c 5 100 (10)
that is, the same as Eq 3.
This means that a given point in the color triangle unambiguously represents all colors with a certain composition of white-
ness (w), blackness (s) and NCS chromaticness (c), that is, all colors with the same NCS nuance. To determine the location of
the point and thereby the NCS nuance, it is sufficient to indicate
...