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1、BRITISH STANDARD BS 950-2:1967 Incorporating Amendment No. 1 Specification for Artificial daylight for the assessment of colour Part 2: Viewing conditions for the graphic arts industry Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GMT+00:00 2006, Unco
2、ntrolled Copy, (c) BSI BS 950-2:1967 This Part of BS 950, having been approved by the Photographic Industry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Council on 28 April 1967 BSI 10-1999 BS 950 first publi
3、shed March 1941 First revision published separately as BS 950-1:1967 BS 950-2 first published April 1967 The following BSI references relate to the work on this standard: Committee references PHC/14, PHC/14/1 Draft for comment D64/10006 ISBN 0 580 35505 5 Co-operating organizations The Photographic
4、Industry Standards Committee under whose supervision this Part of BS 950 was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Aslib Board of Trade British Kinematograph, Sound and Television Society British Photographic Manu
5、facturers Association* British Scientific Instrument Research Association Electric Lamp Industry Council* Federation of Master Process Engravers* H.M. Stationery Office Illuminating Engineering Society* Institute of Incorporated Photographers Institute of Physics and The Physical Society* Institute
6、of Reprographic Technology Ministry of Defence, Navy Department Ministry of Health National Physical Laboratory (Ministry of Technology) Photographic Dealers Association Post Office Royal Photographic Society* Scientific Instrument Manufacturers Association Wholesale Photo Finishers Association The
7、scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committees entrusted with the preparation of this British Standard: Advertising Association Association of Manufacturers and Suppliers for the Graphic Arts
8、 Association of Teachers of Printing and allied subjects British Federation of Master Printers British Printing Machinery Association Institute of Practitioners in Advertising Printing, Packaging and Allied Trades Research Association Society of Lithographic artists, Designers, Engravers an Appendix
9、 is provided to assist manufacturers. 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. Sum
10、mary of pages This document comprises a front cover, an inside front cover, pages i and ii, 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. Licensed C
11、opy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 950-2:1967 BSI 10-19991 1 Scope This Part specifies the spectral distribution of the illumination and also the viewing conditions under which transparent, or reflecting
12、originals, may be compared with their reproductions. The conditions should also be used for viewing originals, particularly transparancies, when selecting them for reproduction. 2 Illuminant The light falling on the viewing surface shall be of the composition specified in Table 11), subject to a tol
13、erance of 15 %; where two contiguous bands deviate in the same sense the mean deviation of the two bands shall not exceed 7.5 %. Table 1 Spectral distribution (visible light) Fluorescent brighteners as commonly occurring in white papers have negligible effect on colour reproduction. When illuminatin
14、g reflective originals or reproductions which flouresce under ultra-violet light it will be necessary to provide for spectral bands U.V.I and U.V.II as specified in Table 2 subject to a tolerance of 30 %. Table 2 Spectral distribution (U.V. light) 3 Levels of illumination and luminance 3.1 The avera
15、ge level of illumination for viewing by reflection shall be 2 200 470 lx (204 43 lm/ft2) and of such degree of uniformity that, if a uniform sheet of white paper of the maximum size of the original or reproduction is placed in the viewing position, it shall appear uniformly illuminated. 3.2 For view
16、ing transparencies, the luminance of the viewing screen field shall be 1 400 300 cd/m2 (408 87 foot-lamberts). The luminance over this area shall appear uniform and this may be judged satisfactorily by viewing the illuminated area through a neutral density filter of density 1.0. 3.3 Disturbing glare
17、 from light sources and reflecting surfaces shall be avoided. 4 Surround Any external lighting, including that from reflecting surfaces, shall not interfere with the nature and intensity of the viewing light so as to cause the limits specified for this by clause 2 and 3 to be exceeded, and it shall
18、not interfere with the state of visual adaptation of the observer. Any uncovered areas of surfaces for viewing by reflection shall be mid-grey. 5 Conditions for transparencies 5.1 The transparency shall be illuminated from behind by diffuse light and shall be surrounded by an illuminated area at lea
19、st 50 mm in width on at least three sides. The surround shall appear to be evenly illuminated and the average level of illumination shall be not less than one half of the maximum level in the viewing screen field. 5.2 When the transparencies, or transparency, being viewed occupy an area less than 70
20、 mm 70 mm, then the illuminated surround shall not be greater than four times the area of the transparencies or transparency being viewed. Any illuminated area in excess of this shall be covered with mid-grey opaque material. A transparency mounted with an opaque border may be viewed mounted if the
21、whole occupies an area less than 70 mm 70 mm. 1) It should be emphasized that these values refer to the spectral distribution at the viewing surfaces and not necessarily to that of the direct light from the lamp or lamps. Spectral band Wavelength range Band value for 100 lumen flux (5 000 K) nmlm 14
22、004550.573 24555109.6 351054021.8 454059044.2 559062015.8 66207608.01 Spectral band Wavelength range Band value for 100 lumen flux ( 5 000 ) nmmW U.V.I3003404.7 U.V.II34040022.4 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GMT+00:00 2006, Uncontrolle
23、d Copy, (c) BSI BS 950-2:1967 2 BSI 10-1999 6 Geometry of lighting and viewing The light shall be so incident and the reflecting original, or reproduction, shall be viewed in such a manner that the effects of specular reflection are minimized. 7 Conditions for side-by-side comparison 7.1 When a side
24、-by-side comparison of a reproduction with a reflecting original is made they shall be viewed in light of the same spectral composition and giving the same level of mean luminance. 7.2 When a side-by-side comparison of a reproduction with a transparency original is made where the illumination for th
25、ese two derives from separate light sources whose band values in a given band deviate in opposite directions then the mean deviation of this band in the two sources shall not exceed 7.5 %2) (15 %2) for U.V. light). The level of illumination on the reflection reproduction and the level of luminance o
26、f the viewing field for the transparency shall be as specified in 3.1 and 3.2 respectively except for the over-riding requirement that the ratio of the luminance of the viewing screen to that of a perfect diffuser (white) illuminated to the level of the reflection reproduction shall be 2.0 0.2 : 1.
27、2) These tolerances are more likely to be achieved by ensuring that the light sources used for illuminating the transparency and the reflection print are of the same make, and preferably of similar age. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GM
28、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 950-2:1967 BSI 10-19993 Appendix A Spectral power distribution of artificial daylight (5 000 K) Values derived from 1965 CIE Recommendations Appendix B Design of practical installations B.1 Lighting Lighting meeting the requirements of Clause 2 may (with t
29、he exception of the ultra-violet bands) be achieved in practice by mixing the light from tungsten filament lamps operating at a colour temperature of 2 400 K with that from fluorescent tubes of the light blue type which have peak visible output at about 475 nm. The mixture must be in equal luminous
30、proportions; for example, if an illumination band of 2 200 lx (204 lm/ft2) is required then 1 100 lx (102 lm/ft2) must be provided by the tungsten filament lamps and 1 100 lx (102 lm/ft2) by the light blue fluorescent tubes. As a guide, 240 V, 60 W tungsten filament vacuum rough service lamps have a
31、 colour temperature of approximately 2 400 K and a luminous efficiency of 8 lm/W; light blue fluorescent tubes have an efficiency of approximately 40 lm/W average through life. Hence assuming equal utilization of light output the ratio of power required by tungsten lamps to those required by fluores
32、cent lamps is 5 : 1. Precise figures cannot be given as these will depend on the design of the fittings. Alternatively, the required illumination may be achieved by using a lamp complying with the requirements of Part 1 together with a suitable filter to convert the output to the requirements of Tab
33、le 1. B.2 Design of fittings general considerations It is important that each lighting fitting produces a correct mixture of light from the fluorescent tubes and tungsten filament lamps, and that all transmitting and reflecting components are neutral in colour. The two types of light source should b
34、e so arranged as to maintain light of unchanging spectral composition over the viewing plane. The light output of fluorescent tubes varies with the glass wall temperature. Consequently adequate ventilation should be provided and radiant heat from adjacent filament lamps must be minimized. Metallic s
35、heeting, painted with a matt and neutral finish3), or anodized aluminium sheeting may be used to lessen heat radiation between lamps whilst still maintaining a high light output from the fittings. Wavelength Relative power per unit wavelength Wavelength Relative power per unit wavelength nmnm 300 31
36、0 320 0.02 2.0 7.8 550 560 570 102.3 100.0 97.7 330 340 350 14.8 17.9 21.0 580 590 600 98.9 93.5 97.7 360 370 380 23.9 26.9 24.5 610 620 630 99.3 99.0 95.7 390 400 410 29.8 49.3 56.5 640 650 660 98.8 95.7 98.2 420 430 440 60.0 57.8 74.8 670 680 690 103.0 99.1 87.4 450 460 470 87.2 90.6 91.4 700 710
37、720 91.6 92.9 76.8 480 490 500 95.2 92.0 95.7 730 740 750 86.6 92.6 78.2 510 520 530 96.6 97.1 102.1 760 770 780 57.7 82.9 78.3 540100.8 3) BS 354, “Recommendations for photometric integrators” gives details of suitable paints. Licensed Copy: London South Bank University, London South Bank Universit
38、y, Fri Dec 08 01:13:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 950-2:1967 4 BSI 10-1999 To adjust for evenness of illumination and correct spectral composition the light sources should be switched on independently and the level of illumination provided by the light blue fluorescent tubes made
39、equal to that from the tungsten filament lamps. In making the measurement it should be noted that illumination meters usually require correction to match their spectral response to that of the normal human eye. B.3 Relative arrangement of fittings for viewing by reflection Specular reflection of the
40、 light source in the direction of the observer should be minimized in order to reduce the effects of 1) imaging of the light source, 2) discomfort glare, 3) desaturation of colours. Difficulties arising from 1) and 2) are obvious in the case of glossy originals or reproductions. However, even with s
41、emi-matt materials the specular reflection which occurs at the top surface is normally uncoloured and consequently adds “white light” to any reflected colour, so desaturating it; a misleading effect which is not always noticed. Problems of matching are particularly difficult when the original and re
42、production have different surface textures. Lighting from above involves elaborate optical design of the lighting fittings if the viewing surface is to be evenly illuminated and viewed normally. Tilting the viewing surface only serves to increase the effects of specular reflection. Most of the diffi
43、culties of the overhead arrangement can be overcome by placing the lighting fittings vertically at either side of an almost vertical viewing surface. Apparatus to meet the requirements of this British Standard requires careful design. One way is to use simple reflectors pivotable about their vertica
44、l axes and suspended from horizontal radius arms attached to a wall behind the viewing surface. To avoid the introduction of objectionable specular reflection, a stop should be provided to prevent the fittings from being swung too far forward. B.4 Arrangement of fittings for transparency viewing The
45、 light sources required behind the transparency should be housed in a well-ventilated container. It should be of sufficient size to ensure adequate mixing of the light from the sources when light blue fluorescent tubes and tungsten filament lamps are used. The internal surfaces of the container shou
46、ld have neutral reflecting characteristics. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 5blank Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 01:13:37 GMT+00:00 2006,
47、Uncontrolled Copy, (c) BSI BS 950-2:1967 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by R
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