1、BRITISH STANDARD BS ISO 21550:2004 Photography Electronic scanners for photographic images Dynamic range measurements ICS 37.040.10 BS ISO 21550:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 September 2004 BSI 30 September 2004 ISBN
2、 0 580 44528 3 National foreword This British Standard reproduces verbatim ISO 21550:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography, which has the responsibility to: A list of organizations represen
3、ted on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using t
4、he “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from
5、legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK
6、. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 14, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued s
7、ince publication Amd. No. Date Comments Reference number ISO 21550:2004(E) OSI 4002INTERNATIONAL STANDARD ISO 21550 First edition 2004-10-01 Photography Electronic scanners for photographic images Dynamic range measurements Photographie Scanners lectroniques pour images photographiques Mesurages din
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13、 O4002(E) I SO 4002 All irthgs ersedevr iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 1 4 Test chart . 4 4.1 Representation and recommended size .4 4.2 The reflective test chart 5 4.3 The transparent test chart 6 5 Test conditions 6 5.1 Gen
14、eral. 6 5.2 Temperature and relative humidity . 6 5.3 Luminance and colour measurements .7 5.4 Scanner settings . 7 6 Measuring the Scanner OECF . 7 6.1 General. 7 6.2 Scanner settings . 7 7 Calculation of the scanner dynamic range. 8 7.1 Luminance OECF 8 7.2 Scanner dynamic range 8 7.3 Determinatio
15、n of the signal to noise ratio 8 8 Presentation of results . 9 8.1 General. 9 8.2 Scanner OECF . 10 8.3 Scanner dynamic range measurements. 11 Annex A (normative) Scanner OECF Test Patches. 12 Annex B (normative) Density shift to measure ISO scanner d max . 13 Bibliography . 14 BSISO21550:2004IS:055
16、12 O4002(E) iv I SO 4002 All irthgs ersedevrForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each membe
17、r body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Elec
18、trotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopt
19、ed by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of paten
20、t rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21550 was prepared by Technical Committee ISO/TC 42, Photography. BSISO21550:2004IS:05512 O4002(E) I SO 4002 All irthgs ersedevr vIntroduction The use of scanners to provide digital image files is rapidly
21、growing. A standard is needed in order to measure the ability of scanners to capture tones especially in the dark areas of the original. At the present time most manufacturers calculate the dynamic range from the bit depth of the implemented A/D conversion which is usually higher than the actual cap
22、abilities of the scanner. This International Standard can be used for photofinishing, professional, graphic arts and consumer scanners. This International Standard specifies methods for measuring the ability of scanners to capture tones especially in the dark areas of the original. The scanner measu
23、rements described in this International Standard are performed in the digital domain, using digital analysis techniques. A test chart of appropriate size and characteristics is scanned and the resulting data is analysed. The test chart described in this International Standard is designed specificall
24、y to evaluate continuous tone film and reflection scanners. It is not designed for evaluating electronic still-picture cameras, video cameras, or bi-tonal document scanners. BSISO21550:2004blank 4002:05512OSISBINTENRATIONAL TSANDADR IS:05512 O4002(E)I SO 4002 All irthgs ersedevr 1Photography Electro
25、nic scanners for photographic images Dynamic range measurements 1 Scope This International Standard specifies methods for measuring and reporting the dynamic range of electronic scanners for continuous tone photographic media. It applies to scanners for reflective and to scanners for transmissive me
26、dia. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5-2, Photography
27、Density measurements Part 2: Geometric conditions for transmission density ISO 5-4, Photography Density measurements Part 4: Geometric conditions for reflection density ISO 554, Standard atmospheres for conditioning and/or testing Specifications ISO 12231, Photography Electronic still-picture camera
28、s Terminology ISO 12232:1998, Photography Electronic still-picture cameras Determination of ISO speed ISO 14524, Photography Electronic still-picture cameras Methods for measuring opto-electronic conversion functions (OECFs) 3 Terms and definitions For the purposes of this document, the terms and de
29、finitions given in ISO 12231 and the following apply. 3.1 addressable photoelements number of active photoelements in an image sensor NOTE This is equal to the number of active lines of photoelements, multiplied by the number of active photoelements per line. 3.2 aliasing output image artefacts that
30、 occur in a sampled imaging system for input images having significant energy at frequencies higher than the Nyquist frequency of the system 3.3 digital output level numerical value assigned to a particular output level, also known as the digital code value BSISO21550:2004IS:05512 O4002(E) 2 I SO 40
31、02 All irthgs ersedevr3.4 edge spread function ESF normalized spatial signal distribution in the linearized output of an imaging system resulting from imaging a theoretical infinitely sharp edge 3.5 effectively spectrally neutral characteristic of an imaging system whereby the output is the same as
32、that produced from a spectrally neutral object 3.6 electronic scanners for photographic film scanner that incorporates an image sensor whose output is a digital signal that represents a still film image 3.7 fast scan direction scan direction corresponding to the direction of the alignment of the add
33、ressable photoelements in a linear array image sensor 3.8 gamma correction process that alters the image data in order to modify the tone reproduction 3.9 image sensor electronic device that converts incident electromagnetic radiation into an electronic signal; e.g. a charge coupled device (CCD) arr
34、ay 3.10 incremental gain function change in output level (digital code value) divided by the change in input level (luminance or exposure) as a function of input level NOTE 1 For the determination of incremental gain values, log input values are not used. NOTE 2 If the input exposure points are very
35、 finely spaced and the output noise is small compared to the quantization interval, the incremental gain function may have a jagged shape. Such behaviour is an artefact of the quantization process and should be removed by using an appropriate smoothing algorithm, or by fitting a smooth curve to the
36、data. In some cases it may be desirable to fit a curve to the input-output data and then determine the incremental gain function by taking the first derivative of the function used for the curve fit. 3.11 incremental output signal input level multiplied by the system incremental gain at that level 3
37、.12 incremental signal to noise ratio ratio of the incremental output signal to the root-mean-squared (rms) noise level, at a particular signal level NOTE This is typically expressed as a graph or table showing the rms noise level versus output signal level for the full range of output signal levels
38、. 3.13 ISO scanner dynamic range difference of the maximum density where the incremental gain is higher than 0,5, as determined according to ISO 21550 to the minimum density that appears unclipped BSISO21550:2004IS:05512 O4002(E) I SO 4002 All irthgs ersedevr 33.14 noise unwanted variations in the r
39、esponse of an imaging system 3.15 resolution measure of the ability of a digital image capture system, or a component of a digital image capture system, to capture fine spatial detail NOTE Resolution measurement metrics include resolving power, limiting visual resolution, SFR, Modulation Transfer Fu
40、nction (MTF) and Contrast Transfer Function (CTF). 3.16 sampled imaging system imaging system or device which generates an image signal by sampling an image at an array of discrete points, or along a set of discrete lines, rather than a continuum of points NOTE The sampling at each point is done usi
41、ng a finite size sampling aperture or area. 3.17 sample spacing physical distance between sampling points or sampling lines NOTE 1 The sample spacing may be different in the two orthogonal sampling directions. NOTE 2 Measured in units of distance (e.g. microns, mm). 3.18 sampling frequency reciproca
42、l of sample spacing NOTE This is expressed in samples per unit distance e.g. dots per inch (dpi). 3.19 scanner electronic device that converts a fixed image, such as a film or film transparency, into an electronic signal 3.20 scanner opto-electronic conversion function Scanner OECF relationship betw
43、een the input density and the digital output levels for a scanner 3.21 slow scan direction direction in which the scanner moves the photoelements (perpendicular to the lines of active photoelements in a linear array image sensor) 3.22 spatial frequency response SFR measured amplitude response of an
44、imaging system as a function of relative input spatial frequency NOTE The SFR is normally represented by a curve of the output response to an input sinusoidal spatial luminance distribution of unit amplitude, over a range of spatial frequencies. The SFR is normalized to yield a value of 1,0 at a spa
45、tial frequency of 0. 3.23 spectrally neutral test chart equality of the relative spectral power distributions of the incident and reflected (or transmitted) light BSISO21550:2004IS:05512 O4002(E) 4 I SO 4002 All irthgs ersedevr3.24 test chart arrangement of test patterns designed to test particular
46、characteristics 3.25 test pattern specified arrangement of spectral reflectance or transmittance characteristics used in measuring an image quality attribute 3.26 test pattern types 3.26.1 bi-tonal patterns patterns that are spectrally neutral or effectively spectrally neutral, and consist exclusive
47、ly of two reflectance or transmittance values in a prescribed spatial arrangement NOTE Bi-tonal patterns are typically used to measure resolving power, limiting resolution and SFR. 3.26.2 grey scale patterns patterns that are spectrally neutral or effectively spectrally neutral, and consist of a lar
48、ge number of different reflectance or transmittance values in a prescribed spatial arrangement NOTE Grey scale patterns are typically used to measure opto-electronic conversion functions. 3.26.3 spectral patterns patterns that are specified by the spatial arrangement of features with differing spect
49、ral reflectance or transmittance values NOTE Spectral patterns are typically used to measure colour reproduction. 4 Test chart 4.1 Representation and recommended size This section defines the type and specifications of the test chart depicted in Figure 1. This test chart can be made at various sizes to correspond to popular film sizes. The recommended size for the reflective version is 100 150 mm and for the transparent
