1、Designation: E2970 14E2970 15Standard Practice forSpecifying Color by the Natural Colour System (NCS)1This standard is issued under the fixed designation E2970; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 The Natural Colour System (NCS) (see 1.7) provides a color notation system that can be used to communicate color. Thispractice i
3、ntroduces 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, providedthe surface is not perceived to be fluorescent or to exhibit direction
4、al color effects.1.3 The system does not include colors that appear to belong to translucent or luminescent objects (so-called volume colors andluminous colors), nor does it include other visual properties of the surface layer, such as gloss and texture. An NCS notation doesnot describe the physical
5、 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 whichare to be u
6、sed in this context.1.5 For the accuracy requirements associated with NCS standards and NCS color samples, the user is referred to SwedishStandard SS 01 91 04 (E).19104. The colored illustrations in this standard shall not be used as standard color samples in any way.Color illustrations that are sho
7、wn on screen or in printouts may be significantly different than the original NCS color samples withthe 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 include
8、d in this standard.1.7 AcknowledgementNCS, Natural Colour System is a trademark of the NCS Colour AB Stockholm, Sweden and is protectedby copyright (). All rights reserved. Original NCS color samples are only available form NCS Colour AB orany authorized NCS distributor. Commercial use of the NCS Sy
9、stem 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 responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulator
10、ylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E284 Terminology of AppearanceE308 Practice for Computing the Colors of Objects by Using the CIE SystemE1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation2.2 Swedish Standards:3SS 01 91 0019100 Colour Notati
11、on systemSS 19102:2004 NCS Colour AtlasSS 01 91 04 (E)19104 NCS colour samples Observation and measurement conditions and tolerances2.3 Other Documents:4CIE 15:2004 Colorimetry1 This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of
12、Subcommittee E12.07 on Color OrderSystems.Current edition approved May 1, 2014Dec. 1, 2015. Published January 2015December 2015. Originally approved in 2014. Last previous edition approved in 2014 as E2970 14. DOI: 10.1520/E2970-14.10.1520/E2970-15.2 For referencedASTM standards, visit theASTM websi
13、te, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 National Colour System (NCS) AB, Box 49022 100 28, Stockholm, Sweden, .Available from Swedish Standards Instit
14、ute, SIS Frlag AB, SE-11880 Stockholm, Sweden, www.sis.se.4 Available from U.S. National Committee of the CIE (International Commission on Illumination) or CIE Webshop http:/ document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes h
15、ave been made to the previous version. Becauseit 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 versionof the standard as published by ASTM is to be considered the official d
16、ocument.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.4 ASTM Adjuncts:Spreadsheet for NCS Notations and CIE Coordinates53. Terminology3.1 Terms and definitions in Terminology E284 are applicable to this practice.3.2 Definitions of
17、 Terms Specific to This Standard:3.2.1 elementary color, none of the six color percepts each of which can be described only by reference to itself.3.2.1.1 DiscussionThe elementary colors, which are designated with uppercase letters, are as follows: white (W), black (S), yellow (Y), red (R), blue(B),
18、 green (G). All other colors can be described in terms of their resemblance to these six. White and black are achromaticelementary colors. Yellow, red, blue and green are chromatic elementary colors.3.2.2 elementary attribute, nthe degree of resemblance of a color to an elementary color.3.2.2.1 Disc
19、ussionThe 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 ele
20、mentary attributes. All are perceptual quantities, which are expressed by a numberbetween 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 el
21、ementary attributes is 100.It follows that a color can have at most four elementary attributes in one of the following combinations:w1s1c11c25 100 (1)where c1 and c2 are adjoining elementary chromatic colors, such as y and r,r and b,b and g, or g and y.3.2.3 full chromatic color, na color that lacks
22、 the elementary attributes of whiteness and blackness.3.2.3.1 DiscussionA full chromatic color, regardless of hue, is designated by an uppercase letter, C. The four chromatic elementary colors Y, R, Band G are also full chromatic colors.3.2.4 NCS chromaticness, nthe degree of resemblance of a color
23、to the full chromatic color of the same hue.3.2.4.1 DiscussionNCS chromaticness is a perceptual quantity derived from the chromatic elementary attributes.The NCS chromaticness is expressedby a number between 0 and 100 for the sum of the (at most two) chromatic elementary attributes, and it is design
24、ated by an italiclowercase c. It follows that:c 5 c11c2 (2)where c1 and c2 are adjoining elementary chromatic colors, such as y and r,r and b,b and g, or g and y.Eq 1 and Eq 2 can then be written:w1s1c 5 100 (3)For achromatic (pure gray) colors including the elementary colors white and black, c = 0
25、and w + s = 100. For maximalcolors, w + s = 0 and c = 100.3.2.5 NCS hue, nthe relation between the (at most two) chromatic elementary attributes of a color, regardless of the whitenessand blackness of the color.3.2.5.1 DiscussionThe NCS hue is a perceptual quantity derived from the chromatic element
26、ary attributes. The NCS hue is expressed by a number5 Available from ASTM International Headquarters. Order Adjunct No. ADJE2970S-EA. Original adjunct produced in 2014.E2970 152between 0 and 100 as the proportion of one chromatic elementary attribute in the sum of the (at most two) chromatic element
27、aryattributes, that is, the NCS chromaticness. The “one” always refers to the chromatic elementary attribute which is placed last inEq 2. In formulae (but not in NCS notations), the hue is denoted by the symbol together with a suffix. The suffix consists ofthe italic lowercase letters for the pair o
28、f chromatic elementary attributes in question, that is, yr,rb,bg, or gy. It follows that:E2970 153yr 5 100 ry 1r! 5100 r c (4)rb 5 100 br 1b! 5 100 bc (5)bg 5 100 gb 1g! 5 100 gc (6)gy 5 100 yg 1y! 5 100 yc (7)Eq 4-7 can also be used in reverse to calculate the chromatic elementary properties when t
29、he NCS chromaticness and NCShue are known.3.2.6 NCS nuance, nthe composition of whiteness, blackness and chromaticness in a color, regardless of the hue.3.2.6.1 DiscussionThe NCS nuance is expressed by a pair of numbers which represent the blackness and chromaticness of the color. The whitenessis ex
30、cluded, since it is given byEq 3. The NCS nuance is a perceptual quantity derived from the elementary attributes. It has an unambiguous NCS notationthrough the first four figures in the alphanumerical basic code.3.2.7 NCS saturation, nthe relation between the chromaticness of a color and its whitene
31、ss, regardless of the hue.3.2.7.1 DiscussionNCS saturation is a perceptual quantity derived from the elementary attributes. The NCS saturation is expressed by a numberbetween 0 and 1 for the ratio of the chromaticness (c) of the color to the sum of its whiteness (w) and chromaticness (c). The NCSsat
32、uration 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, na characteristic of a color such that it appears to have more of the elementary color black or white thananother color.3.2.8.1 DiscussionNCS lightness is a perceptual
33、quantity, designated by a lowercase v, the value of which varies between zero (0) for the elementarycolor black (S) and one (1) for the elementary color white (W) . For achromatic (pure gray) colors including the elementary colorswhite (W) and black (S), for which c = 0, v is defined as:v 5 100 2 s!
34、 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 forwhich the border between specimen and reference i
35、s perceived to be least distinct.3.2.9 luminance factor, Y, nratio of the luminance of a specimen to that of a perfect diffuser, when illuminated and viewedunder specified geometric conditions.3.2.9.1 DiscussionIn the CIE 1931 system, this quantity is tristimulus value Y.4. Summary of Practice4.1 Vi
36、sual MethodObservers should have normal color vision. Specimens should be viewed on an essentially nonselectivegray background of approximately 56 % luminance factor with natural or artificial daylight of approximately 1000 lux. The testspecimen should be compared edge-to-edge to the colors in the N
37、CS 1950 Original Collection (for example, inSS 019102:2004 NCS Colour Atlas). The size of the specimen should be at least 40 by 50 mm with an immediate white surroundof 85 % luminance factor. The specimen and color chip should be perpendicular to the observer with the illumination at an angleof appr
38、oximately 45.4.2 Instrumental MethodCIE 1931 tristimulus values for standard illuminant D65 and the CIE 1931 standard colorimetricobserver are obtained from spectrophotometric or colorimetric measurement. See Practices E308 and E1164. Computation of NCSnotation values can be achieved by following th
39、e directions in Annex A1 and using the tables in the adjunct.5E2970 1545. Significance and Use5.1 The Natural Colour System is a color notation system that builds on how a human being sees color. An NCS notationrepresents a specific color percept and describes the color as perceived; it is not depen
40、dent on limitations caused by pigments, lightrays 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 desi
41、gn. TheNatural Colour System describes colors exactly as they are seen. Any of the millions of colors that exist can be defined within theNCS system and given a precise notation. When the NCS system is known, it is possible to judge the attributes of a color by itsNCS notation; for example, how much
42、 blackness, how much chromaticness, and what hue? This helps to communicate and checkspecifications and to identify colors. Some examples of the use of NCS are: (1)Architects and designers use the NCS color samplesto select colors for all kind of products and materials; (2) They also use the NCS not
43、ation to analyze the colors in use in a particulararea 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 th
44、eirproducts to customers, and (5) Companies use the NCS samples as high quality color standards in corporate identity programs andmanuals.6. Specifying Color with a NCS Notation6.1 NCS NotationAn NCS notation consists of an alpha-numerical code, the letters and figures of which describe theappearanc
45、e of the designated color.6.1.1 The Alpha-numerical CodeThe alpha-numerical basic code for an NCS notation has nine characters, which in turnindicate the blackness and NCS chromaticness, each with two figures (0099), and thereafter the NCS hue by a hyphen followedby two capitals enclosing two figure
46、s (0099). The capitals show the relevant chromatic elementary colors. See Fig. 1. In practicea variation of this basic code with different or fewer characters is often used.6.1.2 A chromatic color with c 100 and with two chromatic elementary attributes is designated by the basic code. Example:5535-R
47、20B designates a color with a blackness of 55, a chromaticness of 35, and a hue of (80 %) red and 20 % blue. Theparentheses are added here to mark that this figure is not shown in the notation.6.1.3 A chromatic color with c 100 and with only one chromatic elementary attribute is designated by a code
48、 which lacks thelast three figures of the basic code. Example: 5535-R.6.1.4 An achromatic (pure gray) color, but not one of the elementary colors white and black is, however, designated by a codewith a capital N instead of the last four figures of the basic code. The capital N means “neutral.” Two e
49、xamples: 2500-N and7000-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 codewith 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 TriangleAn NCS color triangle is an equilateral triangle within which each point unambiguously representsa color wi
