ASTM E2970-14
(Practice)Standard Practice for Specifying Color by the Natural Colour System (NCS)
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 01 91 04 (E).
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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E2970 − 14
StandardPractice 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 responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 The Natural Colour System (NCS) (see 1.7) provides a
bility of regulatory limitations prior to use.
color notation system that can be used to communicate color.
This practice introduces the Natural Colour System, its
2. Referenced Documents
terminology, and conversion to and from CIE tristimulus
2.1 ASTM Standards:
values.
E284 Terminology of Appearance
1.2 The system described in this standard includes color
E308 PracticeforComputingtheColorsofObjectsbyUsing
percepts that appear to belong to the surface of a material,
the CIE System
provided the surface is not perceived to be fluorescent or to
E1164 PracticeforObtainingSpectrometricDataforObject-
exhibit directional color effects.
Color Evaluation
1.3 Thesystemdoesnotincludecolorsthatappeartobelong 3
2.2 Swedish Standards:
to translucent or luminescent objects (so-called volume colors
SS 01 91 00 Colour Notation system
and luminous colors), nor does it include other visual proper-
SS 19102:2004 NCS Colour Atlas
ties of the surface layer, such as gloss and texture. An NCS
SS 01 91 04 (E) NCS colour samples — Observation and
notation does not describe the physical or chemical properties
measurement conditions and tolerances
of an object.
2.3 Other Documents:
1.4 This practice also specifies the conditions for visual or
CIE 15:2004 Colorimetry
instrumental determination of the NCS notation of a color
2.4 ASTM Adjuncts:
sample, defines the relationships between psychometrically 5
Spreadsheet for NCS Notations and CIE Coordinates
determined NCS notations and the corresponding CIE color
coordinates which are to be used in this context.
3. Terminology
1.5 For the accuracy requirements associated with NCS
3.1 Terms and definitions in Terminology E284 are appli-
standards and NCS color samples, the user is referred to
cable to this practice.
Swedish Standard SS 01 91 04 (E).
3.2 Definitions of Terms Specific to This Standard:
1.6 The values stated in SI units are to be regarded as
3.2.1 elementary color, n—oneofthesixcolorperceptseach
standard. No other units of measurement are included in this
of which can be described only by reference to itself.
standard.
3.2.1.1 Discussion—The elementary colors, which are des-
ignated with uppercase letters, are as follows: white (W), black
1.7 Acknowledgement—NCS, Natural Colour System is a
(S), yellow (Y), red (R), blue (B), green (G). All other colors
trademark of the NCS Colour AB Stockholm, Sweden and is
can be described in terms of their resemblance to these six.
protected by copyright (www.ncscolour.com). All rights re-
Whiteandblackareachromaticelementarycolors.Yellow,red,
served. Original NCS color samples are only available form
blue and green are chromatic elementary colors.
NCS Colour AB or any authorized NCS distributor. Commer-
cial use of the NCS System requires a license from NCS Colour
AB.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
1.8 This standard does not purport to address all of the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
safety concerns, if any, associated with its use. It is the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
National Colour System (NCS) AB, Box 49022 100 28, Stockholm, Sweden,
This practice is under the jurisdiction of ASTM Committee E12 on Color and www.ncscolour.com.
Appearance and is the direct responsibility of Subcommittee E12.07 on Color Order Available from U.S. National Committee of the CIE (International Commission
Systems. on Illumination) or CIE Webshop http://www.techstreet.com/cie.
Current edition approved May 1, 2014. Published January 2015. DOI: 10.1520/ Available from ASTM International Headquarters. Order Adjunct No.
E2970-14. 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 − 14
3.2.2 elementary attribute, n—the degree of resemblance of Φ 5 100 r⁄ y 1 r 5 100 r ⁄ c (4)
~ !
yr
a color to an elementary color.
Φ 5 100 b⁄ ~r 1 b! 5 100 b⁄c (5)
rb
3.2.2.1 Discussion—The elementary attributes, which are
Φ 5 100 g⁄ ~b 1 g! 5 100 g⁄c (6)
bg
designated by italic lowercase letters, are: whiteness (w),
Φ 5 100 y⁄ g 1 y 5 100 y⁄c (7)
~ !
blackness (s), yellowness (y), redness (r), blueness (b), and
gy
Eq 4-7 can also be used in reverse to calculate the chromatic
greenness (g). Whitenessand blacknessareachromaticelemen-
elementary properties when the NCS chromaticness and
tary attributes. Yellowness, redness, blueness and greenness are
NCS hue are known.
chromatic elementary attributes. All are perceptual quantities,
which are expressed by a number between 0 and 100. For any
3.2.6 NCS nuance, n—the composition of whiteness, black-
arbitrary color the following apply:
ness and chromaticness in a color, regardless of the hue.
(a) the color cannot simultaneously possess yellowness and
3.2.6.1 Discussion—The NCS nuance is expressed by a pair
blueness,
of numbers which represent the blackness and chromaticness
(b) the color cannot simultaneously possess redness and
of the color. The whiteness is excluded, since it is given by
greenness,
Eq 3. The NCS nuance is a perceptual quantity derived from
(c) the sum of its elementary attributes is 100.
the elementary attributes. It has an unambiguous NCS notation
It follows that a color can have at most four elementary
throughthefirstfourfiguresinthealpha–numericalbasiccode.
attributes in one of the following combinations:
3.2.7 NCS saturation, n—the relation between the chromat-
w1 s1 c 1 c 5 100 (1)
icness of a color and its whiteness, regardless of the hue.
1 2
where c and c are adjoining elementary chromatic
1 2
3.2.7.1 Discussion—NCS saturation is a perceptual quantity
colors, such as y and r, r and b, b and g,or g and y.
derived from the elementary attributes. The NCS saturation is
3.2.3 full chromatic color, n—a color that lacks the elemen-
expressed by a number between 0 and 1 for the ratio of the
tary attributes of whiteness and blackness.
chromaticness (c) of the color to the sum of its whiteness (w)
3.2.3.1 Discussion—A full chromatic color, regardless of
and chromaticness (c). The NCS saturation is designated by an
hue,isdesignatedbyanuppercaseletter, C.Thefourchromatic
italic lowercase m. It follows that:
elementary colorsY, R, B and G are also full chromatic colors.
m 5 c ⁄ ~w 1 c! (8)
3.2.4 NCS chromaticness, n—the degree of resemblance of
where w+c is equal to 100 -s.
a color to the full chromatic color of the same hue.
3.2.4.1 Discussion—NCS chromaticness is a perceptual
3.2.8 NCS lightness, n—a characteristic of a color such that
quantity derived from the chromatic elementary attributes. The it appears to have more of the elementary color black or white
NCS chromaticness is expressed by a number between 0 and than another color.
100 for the sum of the (at most two) chromatic elementary 3.2.8.1 Discussion—NCS lightness is a perceptual quantity,
attributes, and it is designated by an italic lowercase c. It
designated by a lowercase v, the value of which varies between
follows that: zero (0) for the elementary color black (S) and one (1) for the
elementarycolorwhite(W).Forachromatic(puregray)colors
c 5 c 1 c (2)
1 2
including the elementary colors white (W) and black (S), for
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. which c=0, v is defined as:
v 5 ~100 2 s! ⁄ 100 (9)
Eq 1 and Eq 2 can then be written:
The NCS lightness of any arbitrary color specimen is deter-
w1 s1c 5 100 (3)
mined by comparison edge-to-edge with a reference scale of
For achromatic (pure gray) colors including the elementary
achromatic color samples (c = 0). The color specimen is as-
colors white and black, c = 0 and w + s = 100. For maximal
signed the same lightness value as that of the reference
colors, w + s = 0 and c = 100.
sample for which the border between specimen and refer-
ence is perceived to be least distinct.
3.2.5 NCS hue, n—the relation between the (at most two)
chromatic elementary attributes of a color, regardless of the
3.2.9 luminance factor, Y, n—ratio of the luminance of a
whiteness and blackness of the color.
specimen to that of a perfect diffuser, when illuminated and
3.2.5.1 Discussion—The NCS hue is a perceptual quantity
viewed under specified geometric conditions.
derived from the chromatic elementary attributes. The NCS
3.2.9.1 Discussion—IntheCIE1931system,thisquantityis
hue is expressed by a number between 0 and 100 as the
tristimulus value Y.
proportion of one chromatic elementary attribute in the sum of
the (at most two) chromatic elementary attributes, that is, the
4. Summary of Practice
NCS chromaticness. The “one” always refers to the chromatic
4.1 Visual Method—Observers should have normal color
elementary attribute which is placed last in Eq 2. In formulae
vision. Specimens should be viewed on an essentially nonse-
(but not in NCS notations), the hue is denoted by the symbolΦ
lective gray background of approximately 56 % luminance
togetherwithasuffix.Thesuffixconsistsoftheitaliclowercase
factor with natural or artificial daylight of approximately 1000
letters for the pair of chromatic elementary attributes in
lux.The test specimen should be compared edge-to-edge to the
question, that is, yr, rb, bg,or gy. It follows that:
colors in the NCS 1950 Original Collection (for example, in
SS 019102:2004 NCS ColourAtlas). The size of the specimen
should be at least 40 by 50 mm with an immediate white
E2970 − 14
surround of 85 % luminance factor. The specimen and color
chip should be perpendicular to the observer with the illumi-
nation at an angle of approximately 45°.
4.2 Instrumental Method—CIE 1931 tristimulus values for
standard illuminant D65 and the CIE 1931 standard colorimet-
ric observer are obtained from spectrophotometric or colori-
metric measurement. See Practices E308 and E1164. Compu-
For example in the NCS notation 1050-Y90R, 1050 describes the nuance, that
tationofNCSnotationvaluescanbeachievedbyfollowingthe
is, the degree of resemblance to whiteness (40 %) and blackness which is 10 %
directions in Annex A1 and using the tables in the adjunct.
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
5. Significance and Use
(10 %) yellowness. In the NCS notation this is written as yellow with 90 % redness.
(The letter S preceding the complete NCS notation (S 1050-Y90R) denotes an
5.1 The Natural Colour System is a color notation system
NCS notation that is available as standardized physical color samples in SS
that builds on how a human being sees color.An NCS notation
19102:2004 NCS Colour Atlas.
represents a specific color percept and describes the color as
FIG. 1 NCS Notation
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
6.1.1 The Alpha-numerical Code—The alpha-numerical ba-
fields as architecture, corporate identity, cosmetics, education,
sic code for an NCS notation has nine characters, which in turn
fashion and textile forecasting and production, interior design
indicate the blackness and NCS chromaticness, each with two
and product design. The Natural Colour System describes
figures (00–99), and thereafter the NCS hue by a hyphen
colors exactly as they are seen. Any of the millions of colors
followed by two capitals enclosing two figures (00–99). The
that exist can be defined within the NCS system and given a
capitals show the relevant chromatic elementary colors. See
precise notation.When the NCS system is known, it is possible
Fig. 1. In practice a variation of this basic code with different
to judge the attributes of a color by its NCS notation; for
or fewer characters is often used.
example, how much blackness, how much chromaticness, and
6.1.2 Achromaticcolorwithc<100andwithtwochromatic
what hue? This helps to communicate and check specifications
elementaryattributesisdesignatedbythebasiccode.Example:
and to identify colors. Some examples of the use of NCS are:
5535-R20B designates a color with a blackness of 55, a
(1) Architects and designers use the NCS color samples to
chromaticness of 35, and a hue of (80 %) red and 20 % blue.
select colors for all kind of products and materials; (2) They
The parentheses are added here to mark that this figure is not
also use the NCS notation to analyze the colors in use in a
shown in the notation.
particular area and to document their specifications; (3) Com-
6.1.3 A chromatic color with c <100 and with only one
panies use the NCS color samples as the production standards
chromatic elementary attribute is designated by a code which
for their products; (4) Paint manufacturers and other industries
lacks the last three figures of the basic code. Example: 5535-R.
use the NCS notation and the NCS color samples to visualize
6.1.4 An achromatic (pure gray) color, but not one of the
thecoloroftheirproductstocustomers,and(5)Companiesuse
elementary colors white and black is, however, designated by
the NCS samples as high quality color standards in corporate
a code with a capital N instead of the last four figures of the
identity programs and manuals.
basic code. The capital N means “neutral.” Two examples:
2500-N and 7000-N.
6. Specifying Color with a NCS Notation
6.1.5 A full chromatic color, but not one of the elementary
6.1 NCS Notation—An NCS notation consists of an alpha- colors yellow, red, blue or green is, however, designated by a
numerical code, the letters and figures of which describe the codewiththecapitalCinsteadofthefourfirstcharactersofthe
appearance of the designated color. basic code. Example: C-R80B.
The NCS system starts with six elementary colors, which are perceived by human beings as being “pure.” For example, the elementary red color is only red,notared
with a little bit of yellow or a reddish-blue. These
...
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