1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure indexICS 3
2、7.040.10Photography Digital still cameras Determination of BRITISH STANDARDBS ISO 12232:2006BS ISO 12232:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2006 BSI 2006ISBN 0 580 48335 5Cross-referencesThe British Standards which imp
3、lement 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 the “Search” facility of the BSI Electronic Catalogue or of British Standards Online.This publication does not purpo
4、rt 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 legal obligations.Summary of pagesThis document comprises a front cover, an inside front cover, the ISO title page,
5、pages ii to v, a blank page, pages 1 to 17 and a back cover.The BSI copyright notice displayed in this document indicates when the document was last issued.Amendments issued since publicationAmd. No. Date CommentsA list of organizations represented on this committee can be obtained on request to its
6、 secretary. present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK.National forewordThis British Standard reproduce
7、s verbatim ISO 12232:2006 and implements it as the UK national standard. It supersedes BS ISO 12232:1998 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CPW/42, Photography, which has the responsibility to: aid enquirers to understand the text;Referenc
8、e numberISO 12232:2006(E)INTERNATIONAL STANDARD ISO12232Second edition2006-04-15Photography Digital still cameras Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index Photographie Appareils de prises de vue numriques Dtermination de lindice
9、dexposition, des rgimes de vitesse ISO, de la sensibilit normale de sortie et de lindice dexposition recommand BS ISO 12232:2006ii iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative references 1 3 Terms and definitions .1 4 Exposure index values3 4.1 General3 4.2 Focal plane measureme
10、nt.3 4.3 Scene luminance measurement.3 5 Test conditions 4 5.1 General4 5.2 Illumination.4 5.2.1 Daylight illumination .4 5.2.2 Tungsten illumination .4 5.3 Temperature and relative humidity5 5.4 White balance.5 5.5 Infrared (IR) blocking filter5 5.6 Photosite integration time 5 5.7 Compression5 5.8
11、 Other DSC user settings .5 6 Determination of ISO speed5 6.1 General5 6.2 Saturation-based speed 5 6.2.1 Focal plane measurement.6 6.2.2 Scene luminance measurement.6 6.3 Noise-based speed 6 6.3.1 Focal plane method .6 6.3.2 Scene luminance method .7 6.3.3 Colour cameras7 6.3.4 Quantization effects
12、.8 6.4 Method of reporting.8 7 Determination of standard output sensitivity (SOS)8 7.1 Method for calculating SOS9 7.2 Method of reporting.9 8 Specification of recommended exposure index (REI) .9 8.1 Method for calculating recommended exposure index .9 8.2 Method of reporting.10 Annex A (informative
13、) Recommended procedure for determining the noise-based ISO speed.11 Annex B (informative) Scene luminance and focal plane exposure 13 Annex C (informative) Recommended procedure for determining SOS values .14 Annex D (normative) Removing low frequency variations from the image data15 Annex E (infor
14、mative) Calculation of noise-based minimum illumination level.16 Bibliography 17 BS ISO 12232:2006iv Foreword 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
15、 carried out through ISO technical committees. Each member 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 w
16、ork. ISO collaborates closely with the International Electrotechnical 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 Int
17、ernational Standards. Draft International Standards adopted 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
18、the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 12232 was prepared by Technical Committee ISO/TC 42, Photography. This second edition cancels and replaces the first edition (ISO 12232:1998), which
19、 has been technically revised. BS ISO 12232:2006vIntroduction The ISO speed rating, standard output sensitivity (SOS) and recommended exposure index (REI) are important attributes of digital still cameras (DSCs). Standardization assists users and manufacturers in obtaining proper exposures and in de
20、termining the low light capability of DSCs. The exposure level of a DSC is determined by the exposure time, the lens aperture, the lens transmittance, the level and spectral distribution of the scene illumination, and the scene reflectance. When an image from a DSC is obtained using an insufficient
21、exposure, proper tone reproduction can generally be maintained by increasing the electronic or digital gain, but the image will contain an unacceptable amount of noise. As the exposure is increased, the gain can be decreased, and, therefore, the image noise can normally be reduced to an acceptable l
22、evel. If the exposure is increased excessively, the resulting signal in bright areas of the image may exceed the maximum signal level capacity of the image sensor or camera signal processing. This can cause the image highlights to be clipped to form a uniformly bright area, or to bloom into surround
23、ing areas of the image. Therefore, it is important to guide the user in setting proper exposures. An ISO speed rating is intended to serve as such a guide. The methods for assigning an ISO speed rating to a DSC harmonize with current film-based photographic standards. In order to be easily understoo
24、d by photographers, the ISO speed rating for a DSC should directly relate to the ISO speed rating for photographic film cameras. For example, if a DSC has an ISO speed rating of ISO 100, then the same exposure time and aperture should be appropriate for an ISO 100 rated film/process system. The ISO
25、speed ratings described in this International Standard are intended to harmonize with film ISO speed ratings. However, there are differences between electronic and film-based imaging systems that preclude exact equivalency. DSCs can include variable gain and can provide digital processing after the
26、image data has been captured, enabling desired tone reproduction to be achieved over a range of camera exposures. It is therefore possible for DSCs to have a range of speed ratings. This range is defined as the ISO speed latitude. To prevent confusion, a single value is designated as the ISO speed,
27、with the ISO speed latitude upper and lower limits indicating the speed range. BS ISO 12232:2006blank1Photography Digital still cameras Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index 1 Scope This International Standard specifies the me
28、thod for assigning and reporting ISO speed ratings, ISO speed latitude ratings, standard output sensitivity values, and recommended exposure index values, for digital still cameras. This International Standard is applicable to both monochrome and colour digital still cameras. 2 Normative references
29、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 554, Standard atmospheres for conditioning an
30、d/or testing Specifications ISO 7589, Photography Illuminants for sensitometry Specifications for daylight, incandescent tungsten and printer ISO 14524, Photography Electronic still-picture cameras Methods for measuring opto-electronic conversion functions (OECFs) IEC 61966-2-1, Multimedia systems a
31、nd equipment Colour measurement and management Part 2-1: Colour management Default RGB colour space sRGB ITU-R BT.709, Parameter values for the HDTV standards for production and international programme exchange 3 Terms and definitions For the purposes of this document, the following terms and defini
32、tions apply. 3.1 digital still camera DSC device which incorporates an image sensor and which produces a digital signal representing a still picture NOTE A digital still camera is typically a portable, hand-held device. The digital signal is usually recorded on a removable memory, such as a solid-st
33、ate memory card or magnetic disk. 3.2 exposure index EI numerical value that is inversely proportional to the exposure provided to an image sensor to obtain an image NOTE Images obtained from a DSC using a range of exposure index values will normally provide a range of image quality levels. BS ISO 1
34、2232:20062 3.3 exposure series series of images of the same subject taken using different exposure index values 3.4 image sensor electronic device that converts incident electromagnetic radiation into an electronic signal EXAMPLE A charge coupled device (CCD) array. 3.5 ISO speed numerical value cal
35、culated from the exposure provided at the focal plane of a DSC to produce specified camera output signal characteristics using the methods described in this International Standard NOTE The ISO speed is usually the highest exposure index value that still provides peak image quality for normal scenes.
36、 However, a DSC does not necessarily use the ISO speed value as the exposure index value when capturing images. 3.6 ISO speed latitude set of two numerical values calculated from the exposure provided at the focal plane of a DSC to produce specified camera output signal characteristics using the met
37、hods described in this International Standard NOTE The ISO speed latitude needs to correlate with the range of exposure index values that provide acceptable image quality for normal scenes. 3.7 photosite integration time total time period during which the photosites of an image sensor are able to in
38、tegrate the light from the scene to form an image 3.8 recommended exposure index REI specific exposure index value recommended by a DSC provider as a reference for adjusting photographic accessories, as defined in this International Standard NOTE REI provides a practical exposure index value for set
39、ting the reference exposure index of light meters, studio lighting, etc., but images taken using this exposure index value do not necessarily provide the best image quality. 3.9 signal processing operations performed by electronic circuits or algorithms that convert or modify the output of an image
40、sensor 3.10 standard output sensitivity SOS specific exposure index value for a DSC that provides a still image with a specified digital output signal value under specified test conditions, as defined in this International Standard NOTE SOS provides a practical exposure index value based on the sign
41、al level of images captured with a DSC, but images taken using this exposure index value do not necessarily provide the best image quality. BS ISO 12232:200634 Exposure index values 4.1 General An exposure index (EI) is a numerical value that is inversely proportional to the exposure provided to an
42、image sensor to obtain an image. Images obtained from a DSC using a range of EI values will normally provide a range of image quality levels. The ISO speed of a DSC is equal to a particular exposure index value calculated from the exposure provided at the focal plane of the DSC to produce specified
43、camera output signal characteristics, using the methods described in this International Standard. The equations used in this International Standard have been chosen to create a link between electronic and conventional silver-halide-based photographic systems. Using a particular ISO speed value as th
44、e exposure index on a DSC should result in the same camera exposure settings, and resulting focal plane exposures, as would be obtained using the same exposure index on a film camera or other photographic exposure meter. Where possible, the exposure index values corresponding to the arithmetic mean
45、focal plane exposure used to capture an image should be reported in the image file header as the exposure index. 4.2 Focal plane measurement For DSC exposure meters, where the arithmetic mean focal plane exposure is measured within a circle lying in the centre of the image with a diameter of 75/100
46、times the shorter dimension of the image field, the exposure index values, IEI, should be computed using Equation (1), as described in ISO 2721. IEI= 10/Ha(1) where Hais the arithmetic mean focal plane exposure, expressed in lux-seconds (lxs).NOTE 1 The value of 10 as the constant in Equation (1) is
47、 consistent with ISO 2721 and ISO 5763. These International Standards assume that the exposure is an arithmetic mean value, as is normally provided by a camera light meter. If the geometric mean exposure was used in place of the arithmetic mean exposure, a lower value for this constant would be appr
48、opriate. Note that the arithmetic mean exposure is obtained when the linear exposure values are averaged, while a geometric mean exposure is obtained by taking the antilog of the average of the logarithmic exposure values. An approximation to the geometric mean is also obtained by taking the antilog
49、 of the average measured film densities in conventional photographic systems, provided that the film H Lais the arithmetic mean luminance, expressed in candelas per square metre; t is the photosite integration time, expressed in seconds. BS ISO 12232:20064 NOTE The laboratory measurement of L can be simplified by using a full frame uniformly illuminated diffuse reflecting test card, so that the arithmetic mean luminance can be measured by simply measuring the luminance at the centre of the image. The effecti
