Content deleted Content added
don't sell my personal data and use necessarily cookies only Tags: Reverted Mobile edit Mobile web edit |
m Reverted 1 edit by Doorman137 (talk) to last revision by InternetArchiveBot |
||
| (44 intermediate revisions by 33 users not shown) | |||
Line 4:
| 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><
| 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 =
| latest release date = {{Start date and age|
| extended from = [[
| 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, [[
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 metadata tags defined in the Exif standard cover a broad spectrum:
* 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
* Image metrics: Pixel dimensions, resolution, colorspace, and filesize
* Date and time information
* 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 43:
|1.0
|October 1995
|Removed dependencies to io package
|-
|1.1
Line 51:
|2.0
|November 1997
|Licence change to MIT licence
|-
|2.1
Line 59:
|2.2
|April 2002
|Added [[High Efficiency Image File Format|HEIC]] support
|-
|2.21
Line 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.
Line 102 ⟶ 105:
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 library | access-date=2022-07-06 }}</ref> for [[C (programming language)|C]] and Adobe XMP Toolkit<ref>{{cite web | url=https://www.adobe.com/devnet/xmp.html | title=Adobe XMP Toolkit SDK | publisher= Adobe Inc. }}</ref> or Exiv2<ref>{{cite web | url=http://www.exiv2.org/ | title=Exiv2 Image Metadata Library | publisher=Andreas Huggel | access-date=2009-02-12 | archive-date=2012-02-12 | archive-url=https://web.archive.org/web/20120212032622/http://www.exiv2.org/ | url-status=dead }}</ref> for [[C++]], Metadata Extractor<ref>{{cite web | url=http://www.drewnoakes.com/code/exif/ | title=Metadata Extractor | publisher=Drew Noakes | access-date=2011-02-18 | archive-date=2007-09-27 | archive-url=https://web.archive.org/web/20070927201245/http://www.drewnoakes.com/code/exif/ | url-status=dead }}</ref> for [[Java (programming language)|Java]], [[Python Imaging Library|PIL/Pillow]] for [[Python (programming language)|Python]], [[LEADTOOLS]] or [[ExifTool]]<ref>{{cite web | url=http://owl.phy.queensu.ca/~phil/exiftool/ | title=Image::ExifTool Perl library | publisher=Phil Harvey | access-date=2009-02-12}}</ref> for [[Perl]], parse Exif data from files and read/write Exif tag values.
==Problems==
Line 109 ⟶ 112:
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}}
Line 122 ⟶ 125:
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==
Line 134 ⟶ 137:
[[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;"
Line 150 ⟶ 156:
|-
|Orientation (rotation)
|top-left [8 possible values<ref>{{cite web |url=
|-
|Software
Line 236 ⟶ 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==
Line 346 ⟶ 362:
==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]]
Line 367 ⟶ 382:
* [https://cipa.jp/e/std/std-sec.html CIPA Standards - Camera & Imaging Products Association]
* [https://www.cipa.jp/std/documents/download_e.html?DC-008-Translation-2023-E Exif standard version 3.0]
* [https://www.cipa.jp/std/documents/e/DC-X008-Translation-2019-E.pdf Exif standard version 2.32 *New]
* [http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf Exif standard version 2.3]
* Exif standard version 2.2 as [http://www.digicamsoft.com/exif22/exif22/html/exif22_1.htm HTML]
* [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]
* [https://web.archive.org/web/20171124134612/http://www.metadataworkinggroup.org/ Metadata working group]
| |||