1、BRITISH STANDARD BS 950-1:1967 Specification for Artificial daylight for the assessment of colour Part 1: Illuminant for colour matching and colour appraisalBS950-1:1967 This Part of BS950, having beenapproved by the IlluminationIndustry StandardsCommittee and endorsed by the Chairman oftheEngineeri
2、ng Divisional Council, was published under theauthority of the General Council on 24February1967 BSI 10-1999 First published as BS950 March1941 First revision published as BS950-1 February1967 The following BSI references relate to the work on this standard: Committee reference LGE/9 Draft for comme
3、nt D63/6066 ISBN 0 580 35642 6 Co-operating organizations The Illumination Industry Standards Committee under whose supervision this Part of BS950was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Public Lig
4、hting Engineers British Electrical and Allied Manufacturers Association British Glass Industry Research Association British Railways Board Electric Lamp Industry Council* Electric Light Fittings Association* Electricity Council, the Central Electricity Generating Board and the Area Boards in England
5、 and Wales Gas Council Glass Manufacturers Federation* Illumination Engineering Society* Independent Lamp Manufacturers Export Group* Institution of Electrical Engineers Institution of Municipal Engineers London Transport Board* Medical Research Council Ministry of Aviation Ministry of Defence, Navy
6、 Department Ministry of Labour, H.M. Factory Inspectorate Ministry of Public Building and Works* Ministry of Technology Building Research Station* Ministry of Transport National Physical Laboratory (Ministry of Technology)* Post Office Royal Institute of British Architects Society of British Gas Ind
7、ustries Society of Glass Technology* The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Colour Counc
8、il British Leather Manufacturers Research Association Oil and Colour Chemists Association Research Association of British Paint, Colour and Varnish Manufacturers Society of Dyers and Colourists Society of Leather Trades Chemists Society of Motor Manufacturers and Traders Ltd. Textile Institute Amend
9、ments issued since publication Amd. No. Date CommentsBS950-1:1967 BSI 10-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Chromaticity of illuminant 1 4 Spectral distribution of illuminant 3 5 Maintenance of spectral distribution 3 Appendix A
10、 Spectral power distribution of artificial daylight, D6500 4 Appendix B Metameric matches 4 Appendix C Practical sources 4 Figure 1 Chromaticity diagram 2 Table 1 Chromaticity co-ordinates 1 Table 2 Spectral distribution 3BS950-1:1967 ii BSI 10-1999 Preface This British Standard is published under t
11、he joint authority of the Illuminating Industry Standards Committee and the Photographic Industry Standards Committee, and is concerned with the spectral composition of illuminants corresponding to phases of daylight for producing conditions of artificial daylight. The standard is divided into two P
12、arts. Part 1 specifies an illuminant of given chromaticity and spectral distribution with a correlated colour temperature of6500 K, which is suitable for colour matching and colour appraisal. Part2states the viewing requirements applicable only to the graphic arts reproduction industry where a great
13、er red content is required in the spectrum of the illuminant and for which, accordingly, a correlated colour temperature of5000 K has been selected. NOTEWhere metric equivalents are stated the figures in British units are to be regarded as the standard. The metric conversions are approximate. More a
14、ccurate conversions should be based on the tables in BS350, “Conversion factors and tables”. Foreword This Part of the specification is concerned with an illuminant having the spectral composition based on a phase of daylight. As no artificial light source is likely to have this precise spectral com
15、position the tolerances which light sources must meet in order to be suitable for colour matching and colour appraisal are defined. The earlier edition was based on Standard Illuminant C, which had the disadvantages 1) that it is difficult to provide with it high illumination levels over large areas
16、; 2) that its ultra-violet content is inadequate for present-day colour matching in view of the prevalence of fluorescent brightening agents and fluorescent pigments; 3) that its chromaticity is on the purple side of the full radiator locus. New measurements on daylight in this country, and elsewher
17、e, have recently become available (Judd, MacAdam and Wyszecki, J. Opt. Soc. Amer. 54,1031,1964) and the standard is now based on this work instead of on Standard Illuminant C. These measurements, and others of a different type made in recent years at a number of laboratories in this country, indicat
18、e that the chromaticity of daylight most frequently occurring is similar to that adopted in the earlier specification, but on the green side of the full radiator locus. The correlated colour temperature of this region is close to6500 K, and the reconstituted spectral distribution for this colour tem
19、perature has been taken from the work of Judd et al. to provide the standard. The same distribution has recently been recommended by Experts Committee E.1.3.1 of the CIE 1)as Standard Illuminant D6500 (seeAppendix A). A feature of these measurements has been the close similarity of curves from north
20、 sky observations on the one hand, and total sky observations, with or without sunlight, on the other, provided that these conditions refer to similar chromaticities (Henderson and Hodgkiss, Brit. J. Appl. Phys. 14,125,1963;15,947,1964). This specification requires that artificial sources for colour
21、 matching shall satisfy two conditions. The first is that the chromaticity of the light shall lie within certain limits, and the second is that the differences between its spectral distribution and that specified shall be within certain limits. As regards chromaticity the tolerance area is on the gr
22、een side of the full radiator locus, in accordance with most determinations of the chromaticity of natural daylight. Colour matches under sources conforming to this specification will hold in most phases of daylight. As in most cases materials may also be used under artificial light, especially that
23、 from incandescent tungsten lamps, colour matches should be checked under two sources (seeAppendix B). 1) Commission Internationale de lEclairage.BS950-1:1967 BSI 10-1999 iii There are many instances in which a coloured object is inspected, not with a view to matching it with a standard, but to see
24、if it harmonizes with some other coloured objects, or if its colour fits the observers judgement of what is required. This may be called colour appraisal, which in critical cases is most often carried out in daylight. Light sources conforming to the specification are suitable for this purpose. Some
25、information on practical light sources is included inAppendix C. NOTEFluorescent lamps referred to in BS1853, “Tubular fluorescent lamps for general lighting service”, as “colour matching” or “northlight” may not necessarily comply with this specification. Lamps referred to as “daylight” will not co
26、mply with this specification. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of
27、pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 4 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS950-1:1967
28、 BSI 10-1999 1 1 Scope This Part of this British Standard specifies an illuminant representing a phase of daylight, and the tolerances in both chromaticity and spectral distribution to which artificial light sources shall conform. This illuminant is suitable for colour matching and colour appraisal.
29、 2 Definitions For the purposes of this British Standard the following definitions apply: 2.1 ultra-violet range the region of the spectrum which extends from300to400nm 2.2 colour matching the visual comparison under a suitable illuminant of two materials or fields, usually contiguous, for the purpo
30、se of judging their similarity in colour 2.3 colour appraisal the inspection of objects or surfaces under a suitable illuminant with a view to making subjective judgements on their colour characteristics. These judgements may vary between the extremes of colour matching and aesthetic appreciation of
31、 an isolated colour. Further examples are given in the Foreword 3 Chromaticity of illuminant The chromaticity of the illuminant shall fall within the12-sided figure shown in Figure 1 with chromaticity co-ordinates shown in Table 1 and with a centre point given by x =0.3127, y=0.3291, on the1931CIE S
32、ystem. Table 1 Chromaticity co-ordinates NOTEThe area surrounding the centre point is based on the standard deviations in colour matching, as determined by MacAdam (J. Opt. Soc. Amer. 32,247,1942;33,18,1943). This12-sided figure corresponds to a tolerance from the nominal chromaticity of4times the s
33、tandard deviation in the direction of the minor axis, and5times in the direction of the major axis. The purpose of this is to provide an adequate tolerance in lamp manufacture, while keeping well within the limits of daylight variation but avoiding any chromaticity below the full radiator locus. x y
34、 0.3185 0.3192 0.3182 0.3383 0.3361 0.3320 0.3157 0.3125 0.3092 0.3272 0.3228 0.3202 0.3069 0.3062 0.3072 0.3199 0.3221 0.3262 0.3097 0.3129 0.3162 0.3310 0.3354 0.3380BS950-1:1967 2 BSI 10-1999 Figure 1 Chromaticity diagramBS950-1:1967 BSI 10-1999 3 4 Spectral distribution of illuminant The spectra
35、l distribution is based onAppendix A. The spectral band composition and tolerances shall be as shown in Table 2. Table 2 Spectral distribution NOTE 1Bands 1 to 6 are those used in the NPL method of colour rendering assessment (Crawford, Brit. J. Appl. Phys. 14,319,1963). Whereas this method recommen
36、ds the use of10% tolerances on the band values, larger tolerances determined empirically are required at present in this specification to allow for the realization of the standard by fluorescent tubes of varied loading. The tolerances may be altered later if advances are made in providing better lig
37、ht sources. The purpose of these tolerances is to control spectral distribution rather than to assess colour rendering properties. The CIE Test Colour method for measurement of colour rendering (CIE Publication No.13,1965) will be considered later as a requirement in this standard. NOTE 2It is recom
38、mended that the level of illumination for colour matching shall be between70lm/ft 2and300lm/ft 2(750lx and3200lx) and the surroundings shall be neutral in colour. The effects of finishes on lamp reflectors or fittings, or of spectrally selective transmission of plastic diffusers must be borne in min
39、d when lighting installations are planned since these variables may seriously alter the quality of the emitted light. Standardized viewing conditions are also desirable because the level of illumination, background colour and brightness, glare and extraneous lighting will all affect the visual respo
40、nse. Reference should also be made to the publication “The IES Code, Recommendations for good interior lighting”, published by the Illuminating Engineering Society in1961, for further details appropriate to different applications. 5 Maintenance of spectral distribution The manufacturer of a light so
41、urce or colour matching appliance shall declare the average number of hours running during which his product will conform to the specification. Spectral band Wavelength range Band values for 100 lumen flux Percentage tolerance in band value nm mW % U.V.a U.V.b 300340 340400 11.2 43.2 30 30 lm 1 2 3
42、400455 455510 510540 0.79 11.2 23.1 15 15 15 4 5 6 540590 590620 620760 43.7 14.4 6.8 15 15 15BS950-1:1967 4 BSI 10-1999 Appendix A Spectral power distribution of artificial daylight, D6500 Appendix B Metameric matches When two coloured materials have identical spectral reflection curves they will b
43、e a visual match under any illuminant. However, it is possible for two materials to match visually under a given light source without their being a spectral match and such matches are termed “metameric”. They arise because the colouring matters used in each material are different, though this does n
44、ot mean that spectral matches cannot be obtained unless identical colouring matters are used. It is important to detect metamerism because materials which are a metameric match under one illuminant may not match under another illuminant whose spectral characteristics are significantly different. The
45、 simplest method of determining whether a match made under a light source conforming to the standard is metameric or not is to inspect it also under the light from a tungsten filament lamp and, unless it is known that identical colouring matters have been used, it is recommended that this be done. I
46、f the match still holds, it is unlikely to be metameric; if the materials no longer match, but the degree of mis-match is not serious, then it is unlikely that any greater degree of mis-match will occur under any other illuminant, natural or artificial. A metameric match made under a light source co
47、nforming to this specification may not match under certain daylight conditions (e.g.north light from a blue sky or sunlight from a low sun), but it will match under the most frequently occurring phases of daylight. It must be noted, however, that when the degree of metamerism is severe the differenc
48、es in normal colour vision of individual observers may result in two materials being a visual match for some observers, but a mis-match for others. Appendix C Practical sources The specification may be met by using different types of lamp, singly or in combination, with or without filters. If fluore
49、scent lamps are used they should preferably be of low loading types:8ft (2400mm)85W; 5ft(1500mm)65W;4ft (1200mm)40W or2ft(600mm)20W; in order to minimize chromaticity differences and changes of relative ultra-violet emission due to lamp temperature changes. The disadvantages of enclosed unventilated fittings in this respect must also be considered. Wavelength Relative power per unit wavelength Wavelength Relative power per unit wavelength nm nm 300 310 320 0.03 3.3 20.2 550 560 570 104.0 100.0 96.3 330 340 350 37.1 39.9 44.9 5
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