BS-ISO-12231-1997.pdf

BRITISH STANDARD BS ISO 12231:1997 Photography Electronic still picture cameras Terminology ICS 37.040.10 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on 15 September 1997 © BSI 10-1999 ISBN 0 580 28464 6 National foreword This British Standard reproduces verbatim ISO 12231:1997 and implements it as the UK national standard. The UK participation in its preparation was entrusted by Technical Committee CPW/42, Photography, to Subcommittee CPW/42/1, Digital/electronic still picture imaging, which has the responsibility to: 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. A list of organizations represented on this Subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. 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 pages This document comprises a front cover, an inside front cover, pages i and ii, the ISO title page, pages ii to iv, pages 1 to 8 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. Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 © BSI 10-1999i Contents Page National forewordInside front cover Forewordiii Text of ISO 122311 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 ii © BSI 10-1999 Contents Page Forewordiii Introduction1 1Scope1 2Definitions1 Annex (informative) Bibliography8 Index, alphabetical6 Index, by task7 Descriptors: Photography, photographic equipment, electronic equipment, cameras, vocabulary. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 © BSI 10-1999iii 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 carried out through ISO technical committees. Each member body interested in a subject for which a technical commitee 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 Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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. International Standard ISO 12231 was prepared by Technical Committee ISO/TC 42, Photography. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 © BSI 10-19991 Introduction Electronic photography concepts are drawn from traditional photography, electronics, video, and information technology. In some cases the concepts must be redefined to apply to electronic photography. For example, unlike traditional photography, measurements cannot be defined in terms of “film” or “sensitized material”, since images acquired by electronic still cameras are stored electronically and not immediately exposed on film. The meaning of shutters and exposure time is also different for electronic still cameras, because an electronic imaging sensor, usually a charged-coupled device (CCD), has image acquisition characteristics which are different from film. The purpose of this terminology is to standardize the use and meaning of terms associated with electronic still-picture cameras. It is organized alphabetically and follows natural (English) word order whenever possible. The majority of the terms listed in this International Standard are derived from the first three references listed in the Annex. 1 Scope This International Standard defines terms used in electronic photography. Only terms related to electronic still-picture cameras are included. These terms are relevant to the current tasks or of general interest in electronic photography. 2 Definitions The source of most of the terms in this International Standard are the documents on electronic still-picture cameras developed by ISO/TC 42/WG 18 and listed as the first three references in the Annex. Definitions from some existing International Standards, e.g. optical transfer function, are included here for completeness. The term given in angle brackets prior to the definition references one of the first three documents listed in the Annex that serves as the source of the definition. At the end of some definitions, a phrase in italic fount, beginning with cf., lists other terms that are related to the term being defined. 2.1 addressable photoelements The number of active photoelements on an image sensor. This is equal to the number of active lines of photoelements times the number of active photoelements per line NOTEThis term is included to provide an appropriate term for describing the dimensionality of image sensors. The term resolution should not be used when referring to the number of addressable photoelements on an image sensor. 2.2 aliasing Output image artifacts that occur in a sampled imaging system for input images having significant energy at frequencies higher than the Nyquist frequency of the system. Aliasing can be prevented by filtering the input image to suppress these high spatial frequencies prior to sampling, but such filtering may not be desirable 2.3 aliasing ratio The value equal to the “maximum minus minimum” modulation divided by the “average” modulation of an electronic still-picture camera when imaging a frequency burst of constant spatial frequency 2.4 aspect ratio cf. image aspect ratio, pixel aspect ratio 2.5 compression cf. image compression 2.6 edge spread function (ESF) The normalized spatial signal distribution in the output of an imaging system resulting from imaging a theoretical infinitely sharp edge. cf. line spread function, point spread function 2.7 effectively spectrally neutral Having relative spectral radiance characteristics which result in a specific imaging system producing the same output as for a spectrally neutral object. cf. spectrally neutral 2.8 electronic still-picture camera A camera incorporating an image sensor which outputs an analog or digital signal representing a still picture, or records an analog or digital signal representing a still picture on a removable media, such as a memory card or magnetic disk 2.9 electronic shutter Any one of three devices for controlling the exposure time of an electronic still-picture camera. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 2 © BSI 10-1999 2.9.1 electronically shuttered sensor a component of an electronic still camera which electronically controls the image sensor itself in order to set the exposure time 2.9.2 electromechanical shutter a mechanical shutter which is electronically controlled 2.9.3 electro-optical shutter an electronically driven device in front of the sensor which changes the optical path transmittance 2.10 exposure index A numerical value which is inversely proportional to the exposure provided to an image sensor to obtain an image. Images obtained from a camera using a range of exposure index values will normally provide a range of image quality levels. cf. ISO speed of an electronic still-picture camera 2.11 exposure process Various methods to capture images in the electronic still-picture camera. 2.11.1 single exposure acquiring a picture by a single exposure, with one or more image sensors, that exposes all sensor pixels, all colours, and all image locations at the same time 2.11.2 colour sequential acquiring a picture by combining repeated exposures to capture different colour components; for example, by means of three colour illuminations, or by three colour filters 2.11.3 time sequential acquiring a picture by combining repeated exposures to capture different spatial components; for example, with a line array (line scanning) or an area array. With a line sensor, the picture is acquired by optical or physical sub-scanning with an image sensor in one dimension. With an area array, for example, repeated exposures may integrate smaller pictures into a larger picture by means of image sensor shifting 2.12 exposure series A series of images of the same subject taken using different exposure settings 2.13 field/frame Types of picture formats formed by video signals. 2.13.1 field for an interlaced video signal, a “field” is the assembly of alternate (odd or even) lines of a frame. Therefore an interlaced frame is composed of two fields, an odd field and an even field, representing the odd- and even-numbered lines respectively NOTEAdapted from ISO/IEC 13818-2:1996. 2.13.2 frame a frame contains lines of spatial information of a video signal. For progressive video, these lines contain samples starting from one time instant and continuing through successive lines to the bottom of the frame. For interlaced video a frame consists of two fields, an odd field and an even field. One of these fields will commence one field period later than the other NOTEAdapted from ISO/IEC 13818-2:1996. 2.13.3 movie frame or studio frame when interlaced video is applied to still-picture imaging, the resulting movie frame consists of two fields taken simultaneously 2.14 file system The software structure which specifies how the data is logically organized on a given storage media 2.15 gamma correction A process which alters the image data in order to modify the tone reproduction NOTEThe gamma correction is usually an algorithm, lookup table, or circuit which operates separately on each colour component of an image. 2.16 horizontal resolution A resolution value measured in the line readout (fast readout) direction, typically using a vertically oriented resolution wedge 2.17 image aspect ratio The ratio of the image width to the image height. cf. pixel aspect ratio 2.18 image compression A process that alters the way image data is encoded in order to reduce the average size of an image file Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 25 13:44:03 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 12231:1997 © BSI 10-19993 2.19 image data format The structure and content which specifies image data and the organization of the image-related data in a device-independent manner 2.20 image sensor An electronic device which converts incident electromagnetic radiation into an electronic signal; for example, a charge coupled device (CCD) array 2.21 imager size (for an area array sensor) The physical dimensions, height and width, of the photoresponsive area of an imaging sensor NOTEThe following addition is adapted from EIAJ EDX-5301: The measure of imager size for a video-based still-picture camera is described by the approximate diameter of a tube-type image sensor which is equivalent to a diagonal length of the solid state image sensor. The expressions of diameters of 2/3, 1/2, 1/3 or 1/4 inch (type) correspond to actual imager sizes of 6,6 mm × 8,8 mm, 4,8 mm × 6,4 mm, 3,6 mm × 4,8 mm, and 2,7 mm × 3,6 mm respectively, for 4 : 3 image aspect ratio sensors. 2.22 image storage application profile (ISAP) The media profile plus the image data format. cf. media profile, image data format 2.23 ISO speed of an electronic still-picture camera A numerical value calculated from the exposure provided at the focal plane of an electronic camera to produce specified camera output signal characteristics using the methods described in the referenced standard. An ISO speed value of 100 is designated as ISO 100. cf. exposure index 2.24 limiting resolution The value of that portion of a specified resolution test pattern, measured in line widths per picture height (LW/PH), which corresponds to an average modulation value equal to some specified percentage of the modulation value at a specified reference, also measured in LW/PH. For example, the limiting resolution may be the test pattern value, in LW/PH, corresponding to a camera output modulation level of 5 % of the camera output modulation level at a reference frequency of 10 LW/PH. cf. resolution, visual resolution 2.25 line spread function (LSF) The normalized spatial signal distribution in the output of an imaging system resulting from imaging a theoretical infinitely thin line. The LSF is equal to the first derivative of ESF. cf. edge spread function, point spread function 2.26 line widths per picture height (LW/PH) A metric for specifying the width of a solid line on a test chart, relative to the height of the active area of the chart, equal to the height of the active area of the test chart divided by the width of the line. This is equal to the total number of lines of the same width which can be placed edge to edge within the height of a test chart, or within the vertical field of view of a camera. cf. resolution, limiting resolution NOTEThe greater the LW/PH, the smaller the width of the line. Therefore, a camera that distinguishes test patterns having a higher LW/PH has better limiting resolution than one that distinguishes only test patterns having a lower LW/PH. 2.27 media profile The portion of the memory module specification which is specific to a given memory technology; including the form factor, interconnection and access protocol. cf. image storage application profile, image data f