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{{short description|Metadata standard in digital images}}
{{About|a format for storing metadata in image and audio files|information about filename and directory structures of digital cameras|Design rule for Camera File system}}
{{Infobox file format
| screenshot = Epepeotes uncinatus @ Kanjirappally Exif 02.png
| caption = Exif of a file in [[Wikimedia Commons]] (compact form)
| extension = <code>.JPG</code>, <code>.TIF</code>, <code>.WAV</code>, <code>.PNG</code>,<ref name="Extensions to the PNG 1.2 Specification, Version 1.5.0">{{cite web |title=Extensions to the PNG 1.2 Specification, Version 1.5.0 |website=ftp-osl.osuosl.org |url=http://ftp-osl.osuosl.org/pub/libpng/documents/pngext-1.5.0.html#C.eXIf |access-date=4 March 2021}}</ref><code>.WEBP</code><ref name="The Metadata in WEBP (.webp) files">{{cite web |title= The Metadata in WEBP (.webp) files |website=dev.exiv2.org |url=https://dev.exiv2.org/projects/exiv2/wiki/The_Metadata_in_WEBP_files |access-date=16 Feb 2022}}</ref>
| owner = [[Japan Electronic Industries Development Association|JEIDA]], now [[Japan Electronics and Information Technology Industries Association|JEITA]], [[Camera & Imaging Products Association|CIPA]]
| released = {{start date and age|1995}}<ref>{{cite web |url=https://www.loc.gov/preservation/digital/formats/fdd/fdd000146.shtml |title=Exif Exchangeable Image File Format, Version 2.2,Sustainability of Digital Formats: Planning for Library of Congress Collections |website=[[Library of Congress]] |date=26 February 2014 |access-date=2020-08-18}}</ref>
| latest release version = 3.0<ref name="exif30-iptc" />
| latest release date = {{Start date and age|2023|05|df=yes}}<ref name="exif30-iptc" />
| extended from = [[TIFF]], [[JPEG]], [[WAV]]
| extended to = [[Design rule for Camera File system|DCF]]
| standard =
}}
'''Exchangeable image file format''' (officially '''Exif''', according to JEIDA/JEITA/CIPA specifications)<ref>{{Cite web |title=Exif2-1.PDF |url=http://www.exif.org/Exif2-1.PDF |url-status=dead |archive-url=https://web.archive.org/web/20131111073619/http://www.exif.org/Exif2-1.PDF |archive-date=2013-11-11 |format=PDF}}</ref> is a standard that specifies [[file format|formats]] for [[image]]s, [[sound]], and ancillary tags used by [[digital camera]]s (including [[smartphone]]s), [[Image scanner|scanners]] and other systems handling image and sound files recorded by digital cameras. The specification uses the following existing encoding formats with the addition of specific [[Metadata (computing)|metadata]] tags: [[JPEG]] lossy coding for compressed image files, [[TIFF]] Rev. 6.0 ([[RGB color model|RGB]] or [[YCbCr]]) for uncompressed image files, and [[Resource Interchange File Format|RIFF]] [[WAV]] for audio files (linear [[Pulse-code modulation|PCM]] or ITU-T [[G.711]] μ-law PCM for uncompressed audio data, and [[Interactive Multimedia Association|IMA]]-[[Adaptive differential pulse-code modulation|ADPCM]] for compressed audio data).<ref name="auto">{{cite web |url=http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf |title=Standard of the Camera & Imaging Products Association, CIPA DC-008-Translation-2012, Exchangeable image file format for digital still cameras: Exif Version 2.3 |access-date=2014-04-08 }}</ref> It does not support [[JPEG 2000]] or [[GIF]] encoded images.
This standard consists of the Exif image file specification and the Exif audio file specification.
=={{anchor|1.0|1.1|2.0|R98|2.1|2.2|2.21|2.3|3.0}}Background==
Exif is supported by almost all camera manufacturers.
The [[Japan Electronic Industries Development Association]] (JEIDA) produced the initial definition of Exif. Version 2.1 of the specification is dated 12<!-- To be checked: 1 or 12? --> June 1998. [[Japan Electronics and Information Technology Industries Association|JEITA]] established Exif version 2.2 (a.k.a. "'''Exif Print'''"), dated 20 February 2002 and released in April 2002.<ref>{{cite document |author=Technical Standardization Committee on AV & IT Storage Systems and Equipment |title=Exchangeable Image File Format for Digital Still Cameras |id=JEITA CP-3451 |version=Version 2.2 |publisher=[[Japan Electronics and Information Technology Industries Association]] |url=http://www.exif.org/Exif2-2.PDF |date=April 2002 |access-date=2008-01-28}}</ref> Version 2.21 (with [[Adobe RGB]] support) is dated 11 July 2003, but was released in September 2003 following the release of DCF 2.0. The latest version 2.3 was released on 26 April 2010, and revised to 2.31 on July 2013 and revised to 2.32 on 17 May 2019, was jointly formulated by [[Japan Electronics and Information Technology Industries Association|JEITA]] and [[Camera & Imaging Products Association|CIPA]]. Exif is supported by almost all camera manufacturers.▼
The metadata tags defined in the Exif standard cover a broad spectrum:
* Camera settings
* Date and time information. Digital cameras will record the current date and time and save this in the metadata.▼
* Image metrics: Pixel dimensions, resolution, colorspace, and filesize
▲* Camera settings. This includes static information such as the camera model and make, and information that varies with each image such as orientation (rotation), [[aperture]], [[shutter speed]], [[focal length]], [[metering mode]], and [[ISO speed]] information.
▲* Date and time information
* A [[thumbnail]] for previewing the picture on the camera's LCD screen, in file managers, or in photo manipulation software.▼
* Location information
▲* A [[thumbnail]] for previewing the picture on the camera's LCD screen, in file managers, or in photo manipulation software
* Descriptions
* Copyright information
==Version history==
{{Expand section|with=changes|date=August 2020}}
▲The [[Japan Electronic Industries Development Association]] (JEIDA) produced the initial definition of Exif. Version 2.1 of the specification is dated 12
{| class="wikitable"
Line 25 ⟶ 43:
|1.0
|October 1995
|Removed dependencies to io package
|-
|1.1
Line 33 ⟶ 51:
|2.0
|November 1997
|License change to MIT license
|-
|2.1
Line 41 ⟶ 59:
|2.2
|April 2002
|Added [[High Efficiency Image File Format|HEIC]] support
|-
|2.21
Line 67 ⟶ 85:
|
|-
|3.0
|May 2023
|UTF-8 data type
|}
==Technical==
The Exif tag structure is borrowed from TIFF files. On several image specific properties, there is a large overlap between the tags defined in the [[
When Exif is employed for [[JPEG]] files, the Exif data are stored in one of JPEG's defined utility ''Application Segments'', the APP1 (segment marker 0xFFE1), which in effect holds an entire TIFF file within. When Exif is employed in TIFF files (also when used as "an embedded TIFF file" mentioned earlier), the TIFF Private Tag 0x8769 defines a sub-Image File Directory (IFD) that holds the Exif specified TIFF Tags. In addition, Exif also defines a [[Global Positioning System]] sub-IFD using the TIFF Private Tag 0x8825, holding location information, and an "Interoperability IFD" specified within the Exif sub-IFD, using the Exif tag 0xA005.
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Exif data are embedded within the image file itself. While many recent [[Graphics software|image manipulation programs]] recognize and preserve Exif data when writing to a modified image, this is not the case for most older programs. Many image gallery programs also recognise Exif data and optionally display it alongside the images.
Software libraries, such as libexif<ref>{{cite web | url=https://libexif.github.io/ | title=The libexif C EXIF
==Problems==
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The Exif format has a number of drawbacks, mostly relating to its use of legacy file structures.
* The derivation of Exif from the TIFF file structure using offset pointers in the files means that data can be spread anywhere within a file, which means that software is likely to corrupt any pointers or corresponding data that it
* The standard defines a MakerNote tag, which allows camera manufacturers to place any custom format metadata in the file. This is used increasingly by camera manufacturers to store camera settings not listed in the Exif standard, such as shooting modes, post-processing settings, serial number, focusing modes, etc. As the tag contents are proprietary and manufacturer-specific, it can be difficult to retrieve this information from an image or to properly preserve it when rewriting an image. Manufacturers can encrypt portions of the information; for example, some Nikon cameras encrypt the detailed lens data in the MakerNote data.<ref>{{cite web | title=Nikon Tags: Nikon LensData01 Tags | url=http://owl.phy.queensu.ca/~phil/exiftool/TagNames/Nikon.html#LensData01 | publisher=Phil Harvey | date=2008-01-25 | access-date=2008-01-28}}</ref>
* Exif is very often used in images created by scanners, but the standard makes no provisions for any scanner-specific information.{{citation needed|date=November 2014}}
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* There is no way to record time-zone information along with the time, thus rendering the stored time ambiguous. However, time-zone information has been introduced recently by Exif version 2.31 (July 2016). Related tags are: "OffsetTime", "OffsetTimeOriginal" and "OffsetTimeDigitized".
* There is no standard field to record readouts of a camera's [[accelerometers]] or [[inertial navigation system]]. Such data could help to establish the relationship between the image sensor's XYZ coordinate system and the gravity [[Euclidean vector|vector]] (i.e., which way is down in this image). It could also establish relative camera positions or orientations in a sequence of photos. Some software records this information using the GPSImgDirection tag along with custom GPSPitch and GPSRoll tags.<ref>{{Cite web|url=https://www.sno.phy.queensu.ca/~phil/exiftool/geotag.html#Orient|title=Geotagging with ExifTool|website=www.sno.phy.queensu.ca|access-date=2019-10-06}}</ref>
* The XResolution and YResolution tags provide the number of pixels per length unit for the width and height of the image, respectively. (The length unit itself is specified by the tag ResolutionUnit.) By default, these tags in combination are set to 72 [[Pixel density|pixels per inch]] (ppi).<ref>{{cite web |url=https://www.cipa.jp/std/documents/e/DC-X008-Translation-2019-E.pdf |title=CIPA DC-008-Translation-2019 Exchangeable image file format for digital still cameras: Exif Version 2.32 |access-date=August 3, 2021}}</ref> These tags were inherited from the TIFF 6.0 standard and are required<ref>{{cite web |url=https://www.loc.gov/preservation/digital/formats/content/tiff_tags.shtml |author=<!--Not stated--> |title=TIFF Tags |website=[[Library of Congress]] |access-date=August 3, 2021}}</ref> even though for images produced by digital cameras, image resolution values such as ppi are meaningless.<ref>{{cite web |url=http://www.dpiphoto.eu/dpi.htm |title=Dpi, misunderstandings and explanation, what is dpi |last=Weistra |first=Riny |access-date=August 3, 2021}}</ref>
===Privacy and security===
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Since the Exif tag contains metadata about the photo, it can pose a privacy problem. For example, a photo taken with a [[GPS]]-enabled camera can reveal the exact location and time it was taken, and the unique ID number of the device - this is all done by default - often without the user's knowledge. Many users may be unaware that their photos are tagged by default in this manner, or that specialist software may be required to remove the Exif tag before publishing. For example, a [[whistleblower]], journalist or [[political dissident]] relying on the protection of anonymity to allow them to report [[Misfeasance|malfeasance]] by a corporate entity, criminal, or government may therefore find their safety compromised by this default data collection.
In December 2012, anti-virus businessman [[John McAfee]] was arrested in [[Guatemala]] while fleeing from alleged persecution<ref>{{cite web|url=http://www.cnn.com/2012/12/07/world/americas/guatemala-mcafee-asylum-rejected/index.html |title=McAfee wins stay of deportation from Guatemala |date=7 December 2012 |publisher=
According to documents leaked by [[Edward Snowden]], the [[NSA]] is targeting Exif information under the [[XKeyscore]] program.<ref name =Guardian2>{{cite news| author = Staff | title=XKeyscore Presentation from 2008 – Read in Full – Training Materials for the XKeyscore Program Detail How Analysts Can Use It and Other Systems to Mine Enormous Agency Databases and Develop Intelligence from the Web – Revealed: NSA Program That Collects 'Nearly Everything a User Does on the Internet'|url=https://www.theguardian.com/world/interactive/2013/jul/31/nsa-xkeyscore-program-full-presentation|access-date= August 6, 2013|newspaper= [[The Guardian]] |date= July 31, 2013}}</ref>
The privacy problem of Exif data can be avoided by removing the Exif data using a [[metadata removal tool]].<ref>Hassan, Nihad, and Hijazi, Rami. [https://books.google.com/books?id=U-AqDwAAQBAJ
==Related standards==
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[[Extensible Metadata Platform]] (XMP) is an [[List of International Organization for Standardization standards|ISO standard]], originally created by [[ADBE|Adobe Systems Inc.]], for the creation, processing and interchange of standardized and custom metadata for digital documents and data sets. [[IPTC Information Interchange Model|IPTC]] was developed in the early 1990s by the [[International Press Telecommunications Council]] (IPTC) to expedite the international exchange of news among newspapers and news agencies.
==
Not all devices use every available metadata field in the Exif standard.
===Example===
[[File:DigiKam EXIF information screenshot.png|thumb|right|[[DigiKam]] screenshot showing Exif data]]
The following table shows Exif
{| class="wikitable" style="margin:auto;"
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|-
|Orientation (rotation)
|top-left [8 possible values<ref>{{cite web |url=
|-
|Software
Line 218 ⟶ 242:
|(null)
|}
===Time Tags===
In addition to the basic date and time tags (<code>DateTime</code>, <code>DateTimeOriginal</code>, and <code>DateTimeDigitized</code>), there are three corresponding "subsecond" tags: <code>SubsecTime</code>, <code>SubsecTimeOriginal</code>, and <code>SubsecTimeDigitized</code>. The <code>SubsecTime</code> tag is defined in version 2.3 as "a tag used to record fractions of seconds for the DateTime tag;"<ref name="auto"/> the <code>SubsecTimeOriginal</code> and <code>SubsecTimeDigitized</code> fields are defined similarly. The subsecond tags are of variable length, meaning manufacturers may choose the number of ASCII-encoded decimal digits to place in these tags. For <code>DateTime = 2000:01:01 00:00:00</code>, the actual time with various subsecond values would be:
* <code>SubsecTime = 2</code>: <code>2000:01:01 00:00:00.2</code>
* <code>SubsecTime = 23</code>: <code>2000:01:01 00:00:00.23</code>
* <code>SubsecTime = 234</code>: <code>2000:01:01 00:00:00.234</code>
* <code>SubsecTime = 2345</code>: <code>2000:01:01 00:00:00.2345</code>
The standard does not specify which particular event during the "taking" of a picture the time tags should describe. The standard is, in fact, ambiguous. The <code>DateTimeOriginal</code> tag is defined as "The date and time when the original image data was generated." For an exposure—say, 30 seconds—longer than the granularity of the timestamp (one second for the <code>DateTimeOriginal</code> tag), the tag's time could correspond to the beginning of the exposure, the end of the exposure, or some other time. This confusion is exacerbated for the subsecond tags, where the granularity (down to 1/10000th of a second in the examples in the standard) is shorter than many common exposure durations.
As noted above, tags to specify the previously-missing timezone information were added in Exif version 2.31. These are "OffsetTime", "OffsetTimeOriginal" and "OffsetTimeDigitized". They are formatted as seven ASCII characters (including the null terminator) denoting the hours and minutes of the offset, like <code>+01:00</code> or <code>-01:00</code>. The offset is "from UTC (the time difference from Universal Coordinated Time including daylight saving time) of the time of"<ref name="auto"/> the matching tag.
==FlashPix extensions==
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The proprietary formats used by many manufacturers break if the MakerNote tag data is moved (i.e. by inserting or editing a tag that precedes it). The reason to edit to the Exif data could be as simple as to add copyright information, an Exif comment, etc. There are two solutions for this problem:
* When the
* A special offset tag is added. This tag contains the information by how many bytes the MakerNote data was moved in comparison to the original index.
Microsoft has implemented the last solution in Windows 10: In the Windows explorer you can change the
Original index of "MakerNote" = Current index of "MakerNote" - Value of tag "OffsetSchema"
But the tag "OffsetSchema" was defined by Microsoft and it is not part of the official
In some cases, camera vendors also store important information only in proprietary makernote fields, instead of using available Exif standard tags. An example for this is Nikon's ISO speed settings tag.<ref>{{cite web | first=Andreas | last=Huggel | title=Makernote formats and specifications | url=http://www.exiv2.org/makernote.html | date=2012-04-25 | access-date=2012-09-09}}</ref>
==See also==
* [[APEX system]]
* [[Comparison of image viewers]] (Exif view/edit functions)
* [[Design rule for Camera File system]] (DCF)
* [[Digital photography]]
* [[eXtensible Metadata Platform]] (XMP)
* [[
* [[Image file
* [[IPTC Information Interchange Model]]
* [[JPEG File Interchange Format]]
* [[Metadata Working Group]]
* [[Tag Image File Format / Electronic Photography]] (TIFF/EP)
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{{Commons category|Exif}}
* [
* [
* [https://www.cipa.jp/std/documents/e/DC-X008-Translation-2019-E.pdf Exif standard version 2.32]
* [http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf Exif standard version 2.3]
*
* [https://www.loc.gov/preservation/digital/formats/fdd/fdd000146.shtml Exif Exchangeable Image File Format, Version 2.2]
* [https://web.archive.org/web/20131111073619/http://www.exif.org/Exif2-1.PDF Exif standard version 2.1]
* [http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif.html Exif in the TIFF Tag Directory] {{Webarchive|url=https://web.archive.org/web/20171011194110/https://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif.html |date=2017-10-11 }}
* [https://web.archive.org/web/20171124134612/http://www.metadataworkinggroup.org/ Metadata working group]
* [http://www.exiv2.org/metadata.html List of Exif tags including MakerNote tags]
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