Editing Exif

{{short description|Metadata standard in digital images}}
{{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 |date=2017-07-15 |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==
{{ForensicScience|digital}}
Exif is supported by almost all digital 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, digital cameras will record the current (local) date and time set on the device and save this in the metadata
* 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==

The [[Japan Electronic Industries Development Association]] (JEIDA) produced the initial definition of Exif. Version 2.1 of the specification is dated 12 June 1998.{{cn|date=February 2024}} [[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 web |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 |archive-date=2017-12-24 |archive-url=https://web.archive.org/web/20171224163311/http://exif.org/Exif2-2.PDF |url-status=dead }}</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. Version 2.3 was released on 26 April 2010, and revised to 2.31 in 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]]. The latest version, 3.0, was released in May 2023, and brings, among other things, support for UTF-8 to allow text data in non-ASCII encoding.<ref name="exif30-iptc">{{cite web|url=https://iptc.org/news/exif-3-0-released-featuring-utf-8-support/ |website=IPTC |title=Exif 3.0 released, featuring UTF-8 support |date=1 June 2023}}</ref>

{| class="wikitable"
|+Versions
!Version
!Release Date
!Changes
|-
|1.0
|October 1995
|Established basic tag definitions
|-
|1.1
|May 1997
|Added tags and operating specifications
|-
|2.0
|November 1997
|Added sRGB color space, GPS and compressed thumbnails
|-
|2.1
|December 1998
|Added DCF interoperability tags
|-
|2.2
|April 2002
|Applied ExifPrint
|-
|2.21
|September 2003
|Corrections and some additions
|-
|2.21 (unified version)
|September 2009
|More corrections
|-
|2.3
|April 2010
|Added revised ISO tags and lens information
|-
|2.3 (revised)
|December 2012
|Corrections
|-
|2.31
|July 2016
|Added time zone tags and shooting situation tags
|-
|2.32
|May 2019
|Added composite image tags
|-
|3.0
|May 2023
|Added UTF-8 data type
|-
|3.0
|December 2024
|Changed GPSAltitudeRef definition
|}

==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 [[Tag Image File Format|TIFF]], Exif, [[Tag Image File Format / Electronic Photography|TIFF/EP]], and [[Design rule for Camera File system|DCF]] standards. For descriptive metadata, there is an overlap between Exif, [[IPTC Information Interchange Model]] and [[Extensible Metadata Platform|XMP]] info, which also can be embedded in a JPEG file. [[Metadata Working Group|The Metadata Working Group]] has guidelines on mapping tags between these standards.<ref name="mwg_guidance"/>

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.

Formats specified in Exif standard are defined as folder structures that are based on Exif-JPEG and recording formats for memory. When these formats are used as Exif/DCF files together with the DCF specification (for better interoperability among devices of different types), their scope shall cover devices, recording media, and application software that handle them.

==Geolocation==
{{See also|Geotagging}}
The Exif format has standard tags for location information. {{As of | 2014}}, many cameras and mobile phones have a built-in GPS receiver that stores the location information in the Exif header when a picture is taken. Some other cameras have a separate GPS receiver that fits into the flash connector or [[hot shoe]]. Recorded GPS data can also be added to any digital photograph on a computer, either by correlating the time stamps of the photographs with a [[GPS tracking|GPS record]] from a hand-held GPS receiver or manually by using a map or mapping software. Some cameras can be paired with cellphones to provide the geolocation. The process of adding geographic information to a photograph is known as [[Geotagged photograph|geotagging]]. Photo-sharing communities like [[Panoramio]], [[locr]] or [[Flickr]] equally allow their users to upload geocoded pictures or to add geolocation information online.

==Program support==
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==

===Technical===
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 does not decode/encode. For this reason most image editors damage or remove the Exif metadata to some extent upon saving.<ref>{{cite web | title=TIFF Revision 6.0 | url=http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf | publisher=Adobe | date=1992-06-03 | access-date=2009-04-07 | url-status=dead | archive-url=https://web.archive.org/web/20120703095221/http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf | archive-date=2012-07-03 }}</ref>
* 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}}
* Photo manipulation software sometimes fails to update the embedded thumbnail after an editing operation, possibly causing the user to inadvertently publish compromising information.<ref>{{cite web |author=Maximillian Dornseif |title=EXIF Thumbnail in JPEG images |url=http://blogs.23.nu/disLEXia/stories/5751 |publisher=disLEXia 3000 blog |date=2004-12-17 |access-date=2008-01-28 |url-status=dead |archive-url=https://web.archive.org/web/20070928011541/http://blogs.23.nu/disLEXia/stories/5751/ |archive-date=September 28, 2007 }}</ref> For example, someone might blank out a licence registration plate of a car (for privacy concerns), only to have the thumbnail not so updated, meaning the information is still visible.
* Exif metadata are restricted in size to 64 kB in JPEG images because according to the specification this information must be contained within a single JPEG APP1 segment. Although the [[#FlashPix extensions|FlashPix extensions]] allow information to span multiple JPEG APP2 segments, these extensions are not commonly used.  This has prompted some camera manufacturers to develop non-standard techniques for storing the large preview images used by some digital cameras for [[Liquid crystal display|LCD]] review. These non-standard extensions are commonly lost if a user re-saves the image using image editor software, possibly rendering the image incompatible with the original camera that created it.  (In 2009, CIPA released the [[JPEG#JPEG Multi-Picture Format|Multi Picture Object]] specification which addresses this deficiency and provides a standard way to store large previews in JPEG images.<ref>{{cite web |title=Multi-Picture Format |url=http://www.cipa.jp/std/documents/e/DC-007_E.pdf |publisher=CIPA |date=2009-02-04 |access-date=2014-04-29 |archive-url=https://web.archive.org/web/20160405200235/http://cipa.jp/std/documents/e/DC-007_E.pdf |archive-date=2016-04-05 |url-status=dead}}</ref>)
* 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".<ref>{{Cite web |title=Imglift |url=https://exiftool.org/exiftool_pod.pdf |archive-url=https://imglift.com |archive-date=15 November 2005 |access-date=4 February 2020 |publisher=ExifTool User Manual}}</ref>
* 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===

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=CNN |access-date=2012-12-26}}</ref> in neighboring [[Belize]].  ''[[Vice (magazine)|Vice]]'' magazine had published an exclusive interview on their website with McAfee "on the run"<ref>{{Citation |url=https://www.vice.com/en/article/we-are-with-john-mcafee-right-now-suckers/ |title=We Are with John McAfee Right Now, Suckers |publisher=[[Vice (magazine)|Vice]] |date=December 3, 2012 |access-date=7 December 2012}}</ref> that included a photo of McAfee with a ''Vice'' reporter taken with a phone that had geotagged the image.<ref>{{Citation |url=https://thenextweb.com/insider/2012/12/03/vice-leaves-metadata-in-photo-of-john-mcafee-pinpointing-him-to-a-location-in-guatemala/2012/ |title=Vice leaves metadata in photo of John McAfee, pinpointing him to a location in Guatemala |publisher=The Next Web |author=Alex Wilhelm |date=December 3, 2012 |access-date=7 December 2012 |archive-date=6 December 2012 |archive-url=https://web.archive.org/web/20121206022734/http://thenextweb.com/insider/2012/12/03/vice-leaves-metadata-in-photo-of-john-mcafee-pinpointing-him-to-a-location-in-guatemala/2012/ |url-status=dead }}</ref>  The photo's metadata included GPS coordinates locating McAfee in Guatemala, and he was captured two days later.<ref>{{Citation |url=https://www.cbsnews.com/news/john-mcafee-arrested-in-guatemala-for-illegal-entry/ |title=John McAfee arrested in Guatemala for illegal entry |work=[[CBS News]] |date=December 5, 2012 |access-date=7 December 2012}}</ref> McAfee later claimed to have edited the Exif data from his phone to provide a false location.<ref>{{cite web |url=https://thenextweb.com/insider/2012/12/03/it-gets-stranger-now-mcafee-claims-that-he-falsely-edited-the-metadata-on-the-photo-that-placed-him-in-guatemala/ |title=In fresh twist, John McAfee now claims he falsified the metadata of the photo that placed him in Guatemala |author=Alex Wilhelm |date=3 December 2012 |publisher=The Next Web |access-date=5 November 2018}}</ref>

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&dq=exif%20romoval&pg=PA57 Digital Privacy and Security Using Windows: A Practical Guide]. Apress, 2017, pp. 57-59.</ref>

==Related standards==

[[Metadata Working Group]] was formed by a consortium of companies in 2006 (according to their web page) or 2007 (as stated in their own press release). Version 2.0 of the specification was released in November 2010,<ref name="mwg_guidance">{{cite web |title=Guidelines for Handling Image Metadata |url=http://www.metadataworkinggroup.org/pdf/mwg_guidance.pdf |publisher=Metadata Working group |date=2010-11-01 |access-date=2015-05-11 |archive-url=https://web.archive.org/web/20120131102845/http://www.metadataworkinggroup.org/pdf/mwg_guidance.pdf |archive-date=2012-01-31 |url-status=dead}}</ref> giving recommendations concerning the use of Exif, [[IPTC Information Interchange Model|IPTC]] and [[Extensible Metadata Platform|XMP]] metadata in images.

[[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.

==Exif fields==
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 metadata for a photo made with a typical digital camera. Authorship and copyright information is generally not provided in the camera's output, so it must be filled in during later stages of processing. Some programs, such as Canon's [[Digital Photo Professional]], allow the name of the owner to be added to the camera itself.

{| class="wikitable" style="margin:auto;"
|-
!Tag
!Value
|-
|Manufacturer
|CASIO
|-
|Model
|QV-4000
|-
|Orientation (rotation)
|top-left [8 possible values<ref>{{cite web |url=https://www.impulseadventure.com/photo/exif-orientation.html |title=JPEG Rotation and EXIF Orientation / Digital Cameras with Orientation Sensors etc |publisher=Impulseadventure.com |access-date=2012-12-26 |archive-date=2022-03-07 |archive-url=https://web.archive.org/web/20220307162505/https://www.impulseadventure.com/photo/exif-orientation.html |url-status=bot: unknown }}</ref>]
|-
|Software
|Ver1.01
|-
|Date and time
|2003:08:11 16:45:32
|-
|YCbCr positioning
|centered
|-
|Compression
|JPEG compression
|-
|X resolution
|72.00
|-
|Y resolution
|72.00
|-
|Resolution unit
|Inch
|-
|Exposure time
|1/659 s
|-
|F-number
|f/4.0
|-
|Exposure program
|Normal program
|-
|Exif version
|Exif version 2.1
|-
|Date and time (original)
|2003:08:11 16:45:32
|-
|Date and time (digitized)
|2003:08:11 16:45:32
|-
|Components configuration
|Y Cb Cr –
|-
|Compressed bits per pixel
|4.01
|-
|Exposure bias
|0.0
|-
|Max. aperture value
|2.00
|-
|Metering mode
|Pattern
|-
|Flash
|Flash did not fire
|-
|Focal length
|20.1&nbsp;mm
|-
|MakerNote
|432 bytes unknown data
|-
|FlashPix version
|[[FlashPix]] version 1.0
|-
|Color space
|sRGB
|-
|Pixel X dimension
|2240
|-
|Pixel Y dimension
|1680
|-
|File source
|DSC
|-
|Interoperability index
|R98
|-
|Interoperability version
|(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==
The Exif specification also includes a description of FPXR (FlashPix-ready) information, which may be stored in APP2 of [[JPEG]] images using a structure similar to that of a [[FlashPix]] file.<ref>(JEITA CP-3451) Section 4.7.2: Interoperability Structure of APP2 in Compressed Data.</ref>  These FlashPix extensions allow meta-information to be preserved when converting between FPXR JPEG images and FlashPix images.  FPXR information may be found in images from some models of digital cameras by [[Kodak]] and [[Hewlett-Packard]].<ref>{{cite web |url=http://owl.phy.queensu.ca/~phil/exiftool/TagNames/FlashPix.html |title=FlashPix Tags |author=Phil Harvey |date=18 March 2011 |access-date=29 March 2011}}</ref>  Below is an example of the FPXR information found in a JPEG image from a [[Kodak EasyShare V570]] digital camera:

{| class="wikitable" style="margin:auto;"
|-
!Tag
!Value
|-
|Code page
|1200
|-
|Used extension numbers
|1
|-
|Extension name
|Screen nail
|-
|Extension class ID
|10000230-6FC0-11D0-BD01-00609719A180
|-
|Extension persistence
|Invalidated by modification
|-
|Extension create date
|2003:03:29 17:47:50
|-
|Extension modify date
|2003:03:29 17:47:50
|-
|Creating application
|Picoss
|-
|Extension description
|Presized image for LCD
|-
|Storage-stream pathname
|/.Screen Nail_bd0100609719a180
|-
|Screen nail
|(124,498 bytes of data containing 640×480 JPEG preview image)
|}

==Exif audio files==
The Exif specification describes the [[Resource Interchange File Format|RIFF]] file format used for [[WAV]] audio files and defines a number of tags for storing meta-information such as artist, copyright, creation date, and more in these files.<ref>(JEITA CP-3451) Section 5: Exif Audio File Specification.</ref>  The following table gives an example of Exif information found in a WAV file written by the [[PENTAX Optio WP|Pentax Optio WP]] digital camera:

{| class="wikitable" style="margin:auto;"
|-
!Tag
!Value
|-
|Encoding
|Microsoft PCM
|-
|Number of channels
|1
|-
|Sampling rate
|7872
|-
|Avg. bytes per second
|7872
|-
|Bits per sample
|8
|-
|Date created
|2005:08:08
|-
|Exif version
|0220
|-
|Related image file
|IMGP1149.JPG
|-
|Time created
|16:23:35
|-
|Make
|PENTAX Corporation
|-
|Model
|PENTAX Optio WP
|-
|MakerNote
|(2064 bytes of data)
|}

==MakerNote data==
The "MakerNote" tag contains image information normally in a proprietary binary format. Some of these manufacturer-specific formats have been decoded:
* OZHiker (not updated since 2008): Agfa, Canon, Casio, Epson, Fujifilm, Konica/Minolta, Kyocera/Contax, Nikon, Olympus, Panasonic, Pentax/Asahi, Ricoh, Sony<ref>{{cite web |author=Evan Hunter |title=EXIF Makernotes - Reference Information |url=http://ozhiker.com/electronics/pjmt/jpeg_info/makernotes.html |publisher=OZHiker |access-date=2008-01-29}}</ref>
* Kamisaka (not updated since 2007): Canon, Casio, FujiFilm, ISL, KDDI, Konica/Minolta, Mamiya, Nikon, Panasonic, Pentax, Ricoh, Sigma, Sony, WWL<ref>{{cite web |title=Exif MakerNote 解析カイセキ情報 |url=http://homepage3.nifty.com/kamisaka/makernote |publisher=Kamisaka |language=ja |access-date=2008-01-29 |archive-url=https://web.archive.org/web/20081206190200/http://homepage3.nifty.com/kamisaka/makernote/ |archive-date=2008-12-06 |url-status=dead}}</ref>
* X3F Info: Sigma/Foveon<ref>{{cite web |title=SIGMA and FOVEON EXIF MakerNote Documentation |url=http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html  |publisher=x3f.info |access-date=2008-03-26 |archive-url=https://web.archive.org/web/20070805234644/http://www.x3f.info/technotes/FileDocs/MakerNoteDoc.html |archive-date=2007-08-05}}</ref>
* [[ExifTool]]: Canon, Casio, FujiFilm, GE, HP,  JVC/Victor, Kodak, Leaf, Minolta/Konica-Minolta, Nikon, Olympus/Epson, Panasonic/Leica, Pentax/Asahi, Reconyx, Ricoh, Samsung, Sanyo, Sigma/Foveon, Sony, etc.<ref>{{cite web |title=Makernote Types |url=https://exiftool.org/makernote_types.html |website=exiftool.org}}</ref>
* Olypedia: Olympus<ref>{{cite web |title=Olympus Makernotes |url=http://olypedia.de/Olympus_Makernotes |publisher=Olypedia |language=de |access-date=2008-01-29 |archive-url=https://web.archive.org/web/20080119130645/http://olypedia.de/Olympus_Makernotes |archive-date=2008-01-19 |url-status=dead }}</ref>

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 Exif data is saved, the MakerNote data is stored at the same place as before. 
* 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 Exif data of an image file by the properties window. Here the tab sheet "Details" contains some Exif data like title, subject, comments etc. and these Exif data can also be changed and stored. When the image file is saved the tag  "OffsetSchema" (tag ID = 0xea1d) is added and this tag contains a signed 32 bit number. With this number the original index of "MakerNote" can be restored:

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 Exif standard.

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)
* [[Geotagged photograph]]
* [[Image file format]]
* [[IPTC Information Interchange Model]]
* [[JPEG File Interchange Format]]
* [[Metadata Working Group]]
* [[Tag Image File Format / Electronic Photography]] (TIFF/EP)
* [[JEIDA memory card]]

==References==
{{Reflist}}

==External links==
{{Commons category|Exif}}

* [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]
* [http://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf Exif standard version 2.3]
* [http://www.digicamsoft.com/exif22/exif22/html/exif22_1.htm Exif standard version 2.2]
* [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]

{{Graphics file formats}}

[[Category:Digital forensics]]
[[Category:Digital photography]]
[[Category:Graphics file formats]]
[[Category:JPEG]]
[[Category:Metadata]]