1、Designation: E2970 14Standard 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 revision. A n
2、umber 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 acolor notation system that can be used to communicate color.This practice introduces
3、 the Natural Colour System, itsterminology, and conversion to and from CIE tristimulusvalues.1.2 The system described in this standard includes colorpercepts that appear to belong to the surface of a material,provided the surface is not perceived to be fluorescent or toexhibit directional color effe
4、cts.1.3 The system does not include colors that appear to belongto translucent or luminescent objects (so-called volume colorsand luminous colors), nor does it include other visual proper-ties of the surface layer, such as gloss and texture. An NCSnotation does not describe the physical or chemical
5、propertiesof an object.1.4 This practice also specifies the conditions for visual orinstrumental determination of the NCS notation of a colorsample, defines the relationships between psychometricallydetermined NCS notations and the corresponding CIE colorcoordinates which are to be used in this cont
6、ext.1.5 For the accuracy requirements associated with NCSstandards and NCS color samples, the user is referred toSwedish Standard SS 01 91 04 (E).1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 AcknowledgementNCS, Natura
7、l Colour System is atrademark of the NCS Colour AB Stockholm, Sweden and isprotected by copyright (). All rights re-served. Original NCS color samples are only available formNCS Colour AB or any authorized NCS distributor. Commer-cial use of the NCS System requires a license from NCS ColourAB.1.8 Th
8、is standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documen
9、ts2.1 ASTM Standards:2E284 Terminology of AppearanceE308 Practice for Computing the Colors of Objects by Usingthe CIE SystemE1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation2.2 Swedish Standards:3SS 01 91 00 Colour Notation systemSS 19102:2004 NCS Colour AtlasSS 01 91 04 (E
10、) NCS colour samples Observation andmeasurement conditions and tolerances2.3 Other Documents:4CIE 15:2004 Colorimetry2.4 ASTM Adjuncts:Spreadsheet for NCS Notations and CIE Coordinates53. Terminology3.1 Terms and definitions in Terminology E284 are appli-cable to this practice.3.2 Definitions of Ter
11、ms Specific to This Standard:3.2.1 elementary color, none of the six color percepts eachof which can be described only by reference to itself.3.2.1.1 DiscussionThe elementary colors, which are des-ignated with uppercase letters, are as follows: white (W), black(S), yellow (Y), red (R), blue (B), gre
12、en (G). All other colorscan 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.1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct res
13、ponsibility of Subcommittee E12.07 on Color OrderSystems.Current edition approved May 1, 2014. Published January 2015. DOI: 10.1520/E2970-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
14、me information, refer to the standards Document Summary page onthe ASTM website.3National Colour System (NCS) AB, Box 49022 100 28, Stockholm, Sweden,.4Available from U.S. National Committee of the CIE (International Commissionon Illumination) or CIE Webshop http:/ from ASTM International Headquarte
15、rs. Order Adjunct No.ADJE2970S-EA. Original adjunct produced in 2014.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.2 elementary attribute, nthe degree of resemblance ofa color to an elementary color.3.2.2.1 DiscussionThe element
16、ary attributes, which aredesignated by italic lowercase letters, are: whiteness (w),blackness (s), yellowness (y), redness (r), blueness (b), andgreenness (g). Whiteness and blackness are achromatic elemen-tary attributes. Yellowness, redness, blueness and greenness arechromatic elementary attribute
17、s. All are perceptual quantities,which are expressed by a number between 0 and 100. For anyarbitrary color the following apply:(a) the color cannot simultaneously possess yellowness andblueness,(b) the color cannot simultaneously possess redness andgreenness,(c) the sum of its elementary attributes
18、is 100.It follows that a color can have at most four elementaryattributes in one of the following combinations:w1 s1 c11 c25 100 (1)where c1and c2are adjoining elementary chromaticcolors, such as y and r, r and b, b and g,org and y.3.2.3 full chromatic color, na color that lacks the elemen-tary attr
19、ibutes of whiteness and blackness.3.2.3.1 DiscussionA full chromatic color, regardless ofhue, is designated by an uppercase letter, C. The four chromaticelementary colors Y, R, B and G are also full chromatic colors.3.2.4 NCS chromaticness, nthe degree of resemblance ofa color to the full chromatic
20、color of the same hue.3.2.4.1 DiscussionNCS chromaticness is a perceptualquantity derived from the chromatic elementary attributes. TheNCS chromaticness is expressed by a number between 0 and100 for the sum of the (at most two) chromatic elementaryattributes, and it is designated by an italic lowerc
21、ase c. Itfollows that:c 5 c11 c2(2)where c1and c2are adjoining elementary chromaticcolors, such as y and r, r and b, b and g,org and y.Eq 1 and Eq 2 can then be written:w1 s1c 5 100 (3)For achromatic (pure gray) colors including the elementarycolors white and black, c = 0 and w + s = 100. For maxima
22、lcolors, 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 thewhiteness and blackness of the color.3.2.5.1 DiscussionThe NCS hue is a perceptual quantityderived from the chromatic elementary attributes. The NCShue is
23、 expressed by a number between 0 and 100 as theproportion of one chromatic elementary attribute in the sum ofthe (at most two) chromatic elementary attributes, that is, theNCS chromaticness. The “one” always refers to the chromaticelementary attribute which is placed last in Eq 2. In formulae(but no
24、t in NCS notations), the hue is denoted by the symbol together with a suffix. The suffix consists of the italic lowercaseletters for the pair of chromatic elementary attributes inquestion, that is, yr, rb, bg,orgy. It follows that:yr5 100 r y 1 r! 5 100 r c (4)rb5 100 b r 1 b! 5 100 bc (5)bg5 100 g
25、b 1 g! 5 100 gc (6)gy5 100 y g 1 y! 5 100 yc (7)Eq 4-7 can also be used in reverse to calculate the chromaticelementary properties when the NCS chromaticness andNCS hue are known.3.2.6 NCS nuance, nthe composition of whiteness, black-ness and chromaticness in a color, regardless of the hue.3.2.6.1 D
26、iscussionThe NCS nuance is expressed by a pairof numbers which represent the blackness and chromaticnessof the color. The whiteness is excluded, since it is given byEq 3. The NCS nuance is a perceptual quantity derived fromthe elementary attributes. It has an unambiguous NCS notationthrough the firs
27、t four figures in the alphanumerical basic code.3.2.7 NCS saturation, nthe relation between the chromat-icness of a color and its whiteness, regardless of the hue.3.2.7.1 DiscussionNCS saturation is a perceptual quantityderived from the elementary attributes. The NCS saturation isexpressed by a numb
28、er between 0 and 1 for the ratio of thechromaticness (c) of the color to the sum of its whiteness (w)and chromaticness (c). The NCS saturation is designated by anitalic lowercase m. It follows that:m 5 c w 1 c! (8)where w+cis equal to 100 -s.3.2.8 NCS lightness, na characteristic of a color such tha
29、tit appears to have more of the elementary color black or whitethan another color.3.2.8.1 DiscussionNCS lightness is a perceptual quantity,designated by a lowercase v, the value of which varies betweenzero (0) for the elementary color black (S) and one (1) for theelementary color white (W) . For ach
30、romatic (pure gray) colorsincluding the elementary colors white (W) and black (S), forwhich c =0,v is defined as:v 5 100 2 s! 100 (9)The NCS lightness of any arbitrary color specimen is deter-mined by comparison edge-to-edge with a reference scale ofachromatic color samples (c = 0). The color specim
31、en is as-signed the same lightness value as that of the referencesample for which the border between specimen and refer-ence is perceived to be least distinct.3.2.9 luminance factor, Y, nratio of the luminance of aspecimen to that of a perfect diffuser, when illuminated andviewed under specified geo
32、metric conditions.3.2.9.1 DiscussionIn the CIE 1931 system, this quantity istristimulus value Y.4. Summary of Practice4.1 Visual MethodObservers should have normal colorvision. Specimens should be viewed on an essentially nonse-lective gray background of approximately 56 % luminancefactor with natur
33、al or artificial daylight of approximately 1000lux. The test specimen should be compared edge-to-edge to thecolors in the NCS 1950 Original Collection (for example, inSS 019102:2004 NCS Colour Atlas). The size of the specimenshould be at least 40 by 50 mm with an immediate whiteE2970 142surround of
34、85 % luminance factor. The specimen and colorchip should be perpendicular to the observer with the illumi-nation at an angle of approximately 45.4.2 Instrumental MethodCIE 1931 tristimulus values forstandard illuminant D65 and the CIE 1931 standard colorimet-ric observer are obtained from spectropho
35、tometric or colori-metric measurement. See Practices E308 and E1164. Compu-tation of NCS notation values can be achieved by following thedirections in Annex A1 and using the tables in the adjunct.55. Significance and Use5.1 The Natural Colour System is a color notation systemthat builds on how a hum
36、an being sees color. An NCS notationrepresents a specific color percept and describes the color asperceived; it is not dependent on limitations caused bypigments, light rays or nerve signals that have given rise to thisperception. The NCS system is used internationally in suchfields as architecture,
37、 corporate identity, cosmetics, education,fashion and textile forecasting and production, interior designand product design. The Natural Colour System describescolors exactly as they are seen. Any of the millions of colorsthat exist can be defined within the NCS system and given aprecise notation. W
38、hen the NCS system is known, it is possibleto judge the attributes of a color by its NCS notation; forexample, how much blackness, how much chromaticness, andwhat hue? This helps to communicate and check specificationsand to identify colors. Some examples of the use of NCS are:(1) Architects and des
39、igners use the NCS color samples toselect colors for all kind of products and materials; (2) Theyalso use the NCS notation to analyze the colors in use in aparticular area and to document their specifications; (3) Com-panies use the NCS color samples as the production standardsfor their products; (4
40、) Paint manufacturers and other industriesuse the NCS notation and the NCS color samples to visualizethe color of their products to customers, and (5) Companies usethe NCS samples as high quality color standards in corporateidentity programs and manuals.6. Specifying Color with a NCS Notation6.1 NCS
41、 NotationAn NCS notation consists of an alpha-numerical code, the letters and figures of which describe theappearance of the designated color.6.1.1 The Alpha-numerical CodeThe alpha-numerical ba-sic code for an NCS notation has nine characters, which in turnindicate the blackness and NCS chromaticne
42、ss, each with twofigures (0099), and thereafter the NCS hue by a hyphenfollowed by two capitals enclosing two figures (0099). Thecapitals show the relevant chromatic elementary colors. SeeFig. 1. In practice a variation of this basic code with differentor fewer characters is often used.6.1.2 Achroma
43、tic color with c 100 and with two chromaticelementary attributes is designated by the basic code. Example:5535-R20B designates a color with a blackness of 55, achromaticness of 35, and a hue of (80 %) red and 20 % blue.The parentheses are added here to mark that this figure is notshown in the notati
44、on.6.1.3 A chromatic color with c 100 and with only onechromatic elementary attribute is designated by a code whichlacks the last three figures of the basic code. Example: 5535-R.6.1.4 An achromatic (pure gray) color, but not one of theelementary colors white and black is, however, designated bya co
45、de with a capital N instead of the last four figures of thebasic 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 elementarycolors yellow, red, blue or green is, however, designated by acode with the capital C instead of the four fi
46、rst characters of thebasic code. Example: C-R80B.For example in the NCS notation 1050-Y90R, 1050 describes the nuance, thatis, 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 butis the remaining 40 %
47、(100-10-50=40). The hue Y90R describes the degree ofresemblance 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.(The letter S preceding the complete NCS notation (S 1050-Y90R) denotes anNCS notation t
48、hat is available as standardized physical color samples in SS19102:2004 NCS Colour Atlas.FIG. 1 NCS NotationThe 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,notaredwith a little bit of yellow or a
49、 reddish-blue. These six elementary colors correspond with the perception of color in our brain. The four chromatic elementary colors are Yellow(Y), Red (R), Blue (B) and Green (G), and the two non-chromatic elementary colors are White (W) and Black (S). All other colors can be described in terms of their degreeof visual resemblance to the elementary colors. These resemblances are the elementary attributes (yellowness, redness, blueness, greenness, whiteness and bla
