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1、BRITISH STANDARD BS 1384-2: 1993 ISO 5-2: 1991 Photographic density measurements Part 2: Specification for geometric conditions for transmission density UDC 771.534.531.5 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1384-2:1993 This Br
2、itish Standard, having been prepared under the direction of the Cinematography and Photography Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 January 1993 BSI 06-1999 First published August 1947 Second edition August 1986 Third editio
3、n January 1993 The following BSI references relate to tile work on this standard: Committee reference CPM/10 Draft for comment 90/44654 DC ISBN 0 580 21560 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Cinematography and Photography
4、Standards Policy Committee (CPM/-) to Technical Committee CPM/10, upon which the following bodies were represented: British Association of Oral and Maxillo-Facial Surgeons British Dental Association British Kinematograph, Sound and Television Society British Photographic Association College of Radio
5、graphers Institute of Physics Ministry of Defence Photogrammetric Society Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1384-2:1993 BSI 06-1999i Contents Page Committees responsib
6、le Inside front cover National forewordii Introduction1 1Scope2 2Normative references2 3Definitions2 4Coordinate system, terminology and symbols2 5 ISO standard diffuse density2 6ISO standard projection density5 Annex A (informative) Sphere diffuse density6 Annex B (informative) Unmatched influx and
7、 efflux angles6 Annex C (informative) Diffusion coefficient7 Annex D (informative) Bibliography7 Figure 1 Geometry for density measurements3 Figure C.1 Geometrical distribution of diffusing system7 List of references Inside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 G
8、MT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1384-2:1993 ii BSI 06-1999 National foreword This Part of BS 1384 has been prepared under the direction of the Cinematography and Photography Standards Policy Committee. It is one of a series of Parts which together constitute a revision of BS 1384. This
9、Part is identical with ISO 5-2:1991 Photography Density measurements Part 2: Geometric conditions for transmission density published by the International Organization for Standardization (ISO). It supersedes BS 1384-2:1986, which is withdrawn. Cross-references The Technical Committee has reviewed th
10、e provisions of CIE Publication 15-2:1978, to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. There is no corresponding British Standard to CIE 15-2. A British Standard does not purport to include all the necessary pr
11、ovisions 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. International standardCorresponding British Standard ISO 5-1:1984 BS 1384 Photographic density measurements
12、Part 1:1985 Guide for terms, symbols and notations (Identical) ISO 5-3:1984Part 3:1985 Specification for spectral conditions (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard h
13、as 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 Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5-2:1991(E) BSI 06-19991 Introduction
14、 This part of ISO 5 is one of a series which specifies the geometric conditions for transmission densitometry, primarily but not exclusively, as practised in black-and-white and colour photography. The primary change from the first edition (1974) to the second edition (1985) was the replacement of t
15、he integrating sphere method with the “opal-glass” method as the basis for specifying ISO standard diffuse transmission density. (Although any means of diffusion which meets the specifications of this part of ISO 5 may be used, the method is often denoted simply by the words “opal-glass” to differen
16、tiate it from the integrating sphere method.) By that change it was recognized that transmission density measurements of photographic products are almost exclusively made by using diffusers. Slightly smaller density values are obtained compared to those based on the integrating sphere method because
17、 of inter-reflections between the opal-glass and the specimen. The effect is greatest at low densities and dependent on the reflectance characteristics of the opal-glass and the surface of the specimen facing the diffuser. The changes from the second edition are as follows: a) The Halbertsma method
18、for measuring diffusion coefficient has been replaced by a general method intended to describe the illumination distribution incident on the film or receiver. That distribution is influenced by the system not just by the “opal” as “illuminated by normally incident light”, which is prescribed by the
19、Halbertsma method. In other words, a diffuser having a diffusion coefficient of 0,9, measured by the Halbertsma method, may have an entirely different distribution when placed in a system not having normally incident light. b) The diffusion coefficient of an entire system has been defined along with
20、 the method of measurement. c) The system for which the reflectance factor is to be measured has been defined and the method of measurement has been prescribed to achieve consistency of results. d) Since inter-reflections and surface finish play such an important role in the determination of density
21、 with this geometry, the condition that the diffusing system surface be polished was placed in the body of the text instead of in a footnote. e) Wording which fostered inconsistency in interpretation regarding the separation between sample and diffuser has been altered. f) The figure describing geom
22、etry for density measurements was clarified and made more general in order to accommodate both diffuse and projection density. This part of ISO 5 also describes the geometric conditions for two types of projection density. The spectral conditions described are specified in ISO 5-3. Diffuse transmiss
23、ion density is a measure of the modulation of light by a film that is diffusely illuminated on one side and viewed from the other, as when a film is viewed on a diffuse transparency illuminator. The geometric conditions of projection with diffuse illumination are nearly equivalent to the conditions
24、of viewing a film on a diffuse illuminator, the projection lens taking the place of the eye. When film is on a diffuse illuminator or in contact with a print material, light is inter-reflected between the film and the nearby surface. This inter-reflection affects the density and is best taken into a
25、ccount in a measuring instrument by the use of an opal-glass diffuser or integrator, rather than an integrating sphere. Apart from this fundamental reason for using densitometers employing opal-glass diffusers, such instruments are preferred because they are more durable and more convenient to manuf
26、acture and use. Projection density is a measure of the modulation of light by a film that is specularly illuminated on one side and is projected by way of a specular collection system. Equipment employing optical condensers is used to view microfilm, motion pictures, and slides, and to make projecti
27、on prints. The conditions defined in this part of ISO 5 for projection density simulate the geometric conditions affecting the transmitting characteristics of a small area on a negative or transparency at the centre of the frame of a typical projection system employing condensers. The area under con
28、sideration may be defined by a small opening, known as the sampling aperture, in an otherwise opaque sheet in the frame. The ratio of the total flux transmitted by a specimen to the total flux incident on the aperture is defined as transmittance and is of little practical use. However, the flux tran
29、smitted by the sampled area and collected by the projection lens to form the projected image is of interest. The ratio of this flux to the flux collected when there is no film in the sampling aperture is designated transmittance factor, and is used as a basis for calculating projection density. Lice
30、nsed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5-2:1991(E) 2 BSI 06-1999 The measured density depends on the half-angle of the cone of incident rays and the half-angle subtended by the projection lens at the sampling aperture. These half-an
31、gles may be indicated either in degrees or by R-numbers. Since the R-number is usually marked on projection lenses, the two types of projection density specified in this part of ISO 5 are identified by R-numbers, namely R/4,5 and R/1,6. The R/4,5 type is frequently used since it is representative of
32、 microfilm readers. The R/1,6 type is considered representative of motion-picture projectors. 1 Scope This part of ISO 5 specifies the geometric conditions for measuring ISO diffuse and R/4,5 and R/1,6 projection transmission densities. Diffuse density is primarily applicable to measurements of phot
33、ographic images to be viewed on a transparency illuminator, to be contact printed, or to be projected with a system employing diffuse illumination. Projection density is primarily applicable to measurements of photographic images to be projected with systems employing optical condensers. Though prim
34、arily intended for the measurement of photographic images, the densitometric methods specified in this part of ISO 5 are often applied to optical filters and other sheet materials. 2 Normative references The following standards contain provisions which, through reference in this text, constitute pro
35、visions of this part of ISO 5. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 5 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated bel
36、ow. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 5-1:1984, Photography Density measurements Part 1: Terms, symbols and notations. ISO 5-3:1984, Photography Density measurements Part 3: Spectral conditions. CIE Publication 15-2:1978, Recommendations on uni
37、form color spaces Color difference equations Psychometric color terms. 3 Definitions For the purposes of this part of ISO 5, the definitions given in ISO 5-1 and the following definitions apply. 3.1 transmittance factor (T) ratio of the measured flux transmitted by a specimen to the measured flux wh
38、en the specimen is removed from the sampling aperture of the measuring device: 3.2 transmission density (DT) logarithm to the base 10 of the reciprocal of the transmittance factor: 4 Coordinate system, terminology and symbols The coordinate system, terminology, and symbols described in ISO 5-1 are u
39、sed herein as a basis for specifying the geometric conditions for transmission density measurements. 5 ISO standard diffuse density 5.1 Geometric modes Diffuse transmission measurements may be made with a diffuse illuminator and-a directional receiver, this arrangement being known as the “diffuse in
40、flux mode”. Use of directional illumination and a diffuse receiver is known as the “diffuse efflux mode”. The diffuse modes are shown in Figure 1. These modes can be described in terms of a specified diffuse distribution and a specified directional distribution, the distributions being distributions
41、 of radiance or distributions of sensitivity, depending on the mode. where Tis the transmittance factor; is the transmitted flux; is the aperture flux. T 9E 9j - -= 9E 9j DTLog10 1 T - - = Log10 9j 9E - -= Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled C
42、opy, (c) BSI ISO 5-2:1991(E) BSI 06-19993 Figure 1 Geometry for density measurements Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 07:53:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 5-2:1991(E) 4 BSI 06-1999 5.2 Sampling aperture The extent and shape of the area on which density is mea
43、sured is known as the sampling aperture. The size and shape of the sampling aperture is not critical if no dimension is so large that the influx and efflux geometric conditions vary materially over the sampling aperture or so small that the granularity of the film, specimen thickness, or diffraction
44、 effects are significant. Measurements on areas less than 0,5 mm diameter border on or involve micro-densitometry and are subject to special considerations not dealt with in this part of ISO 5. The relative sizes of the sampling aperture and the optical components limiting the directional distributi
45、on are related by the specified tolerances on the angular subtense of the directional distribution. Ideally, the influx and efflux distribution should be uniform over the sampling aperture. When the sampling aperture is scanned laterally with a geometrically similar aperture, similarly oriented and
46、having dimensions no more than one-quarter of those of the corresponding dimensions of the sampling aperture, the radiance at any place on the sampling aperture shall be within 10 % of the maximum value. Lack of uniformity is immaterial when uniform images are measured, but can be an important sourc
47、e of error in measurements on non-uniform images. The size of the diffuser relative to the aperture shall be large enough to prevent its rim or support from affecting density measurement. The specimen to be measured shall be placed in contact with the diffuser. In the case of photographic films and
48、plates, the emulsion surface shall face the diffuser. 5.3 Diffuse distribution The angular distribution of radiance or the angular distribution of sensitivity in the diffuse distribution, at the centre of the sampling aperture, should ideally be uniform throughout the hemisphere bounded by the plane
49、 of the sampling aperture. For the purposes of this part of ISO 5 the degree of uniformity shall be such that the diffusion coefficient shall fall between 0,90 and 1,00 as defined below.1) For the spectral range specified in ISO 5-3, the reflectance factor (as defined by CIE diffuse/normal geometry)2)of the diffuse illuminating (receiving) system shall be 0,55 0,05, and the face shall be polished3). Such a distribution has often been produced by the use of a plate of opal-glass to diffuse the incident flux or integrate the transmitted flux, b