Exif - Wikipedia
Exif
  (Redirected from Exchangeable image file format)
This article is about a format for storing metadata in image and audio files. For information about filename and directory structures of digital cameras, see Design rule for Camera File system.
Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) is a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other systems handling image and sound files recorded by digital cameras. The specification uses the following existing file formats with the addition of specific metadata tags: JPEG discrete cosine transform (DCT)[3] for compressed image files, TIFF Rev. 6.0 (RGB or YCbCr) for uncompressed image files, and RIFF WAV for audio files (Linear PCM or ITU-T G.711 μ-Law PCM for uncompressed audio data, and IMA-ADPCM for compressed audio data).[4] It is not used in JPEG 2000 or GIF.
Exif

Exif of a file in Wikimedia Commons (compact form)
Filename extension.JPG, .TIF, .WAV,
.PNG[1]
Developed byJEIDA, now JEITA, CIPA
Initial release1995; 26 years ago[2]
Latest release
2.32
(26 April 2010; 11 years ago, revised May 2019; 2 years ago)
Extended fromTIFF, JPEG, WAV
Extended toDCF
This standard consists of the Exif image file specification and the Exif audio file specification.
Background
The Japan Electronic Industries Development Association (JEIDA) produced the initial definition of Exif. Version 2.1 of the specification is dated 12 June 1998. JEITA established Exif version 2.2 (a.k.a. "Exif Print"), dated 20 February 2002 and released in April 2002.[5] 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 JEITA and CIPA. Exif is supported by almost all camera manufacturers.
The metadata tags defined in the Exif standard cover a broad spectrum:
Version history
This section needs expansion with: changes. You can help by adding to it. (August 2020)
Versions
VersionRelease DateChanges
1.0October 1995
1.1May 1997
2.0November 1997
2.1December 1998
2.2April 2002
2.21September 2003Addition of "Exif Print"
2.21 (unified version)September 2009
2.3April 2010
2.3 (revised)December 2012
2.31July 2016
2.32May 2019
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 TIFF, Exif, TIFF/EP, and DCF standards. For descriptive metadata, there is an overlap between Exif, IPTC Information Interchange Model and XMP info, which also can be embedded in a JPEG file. The Metadata Working Group has guidelines on mapping tags between these standards.[6]
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 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 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 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[7] for C and Adobe XMP Toolkit[8] or Exiv2[9] for C++, Metadata Extractor[10] for Java, PIL/Pillow for Python, LEADTOOLS or ExifTool[11] 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.
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 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[18] in neighboring Belize. Vice magazine had published an exclusive interview on their website with McAfee "on the run"[19] that included a photo of McAfee with a Vice reporter taken with a phone that had geotagged the image.[20] The photo's metadata included GPS coordinates locating McAfee in Guatemala, and he was captured two days later.[21] McAfee later claimed to have edited the EXIF data from his phone to provide a false location.[22]
According to documents leaked by Edward Snowden, the NSA is targeting Exif information under the XKeyscore program.[23]
The privacy problem of Exif data can be avoided by removing the Exif data using a metadata removal tool.[24]
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,[6] giving recommendations concerning the use of Exif, IPTC and XMP metadata in images.
Extensible Metadata Platform (XMP) is an ISO standard, originally created by Adobe Systems Inc., for the creation, processing and interchange of standardized and custom metadata for digital documents and data sets. 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.
Example
DigiKam screenshot showing Exif data
The following table shows Exif data for a photo made with a typical digital camera. Notice that 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.
TagValue
ManufacturerCASIO
ModelQV-4000
Orientation (rotation)top-left [8 possible values[25]]
SoftwareVer1.01
Date and time2003:08:11 16:45:32
YCbCr positioningcentered
CompressionJPEG compression
X resolution72.00
Y resolution72.00
Resolution unitInch
Exposure time1/659 s
F-numberf/4.0
Exposure programNormal program
Exif versionExif version 2.1
Date and time (original)2003:08:11 16:45:32
Date and time (digitized)2003:08:11 16:45:32
Components configurationY Cb Cr –
Compressed bits per pixel4.01
Exposure bias0.0
Max. aperture value2.00
Metering modePattern
FlashFlash did not fire
Focal length20.1 mm
MakerNote432 bytes unknown data
FlashPix versionFlashPix version 1.0
Color spacesRGB
Pixel X dimension2240
Pixel Y dimension1680
File sourceDSC
Interoperability indexR98
Interoperability version(null)
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.[26] 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.[27] Below is an example of the FPXR information found in a JPEG image from a Kodak EasyShare V570 digital camera:
TagValue
Code page1200
Used extension numbers1
Extension nameScreen nail
Extension class ID10000230-6FC0-11D0-BD01-00609719A180
Extension persistenceInvalidated by modification
Extension create date2003:03:29 17:47:50
Extension modify date2003:03:29 17:47:50
Creating applicationPicoss
Extension descriptionPresized 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 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.[28] The following table gives an example of Exif information found in a WAV file written by the Pentax Optio WP digital camera:
TagValue
EncodingMicrosoft PCM
Number of channels1
Sampling rate7872
Avg. bytes per second7872
Bits per sample8
Date created2005:08:08
Exif version0220
Related image fileIMGP1149.JPG
Time created16:23:35
MakePENTAX Corporation
ModelPENTAX 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:
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:
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.[34]
See also
References
  1. ^ "Extensions to the PNG 1.2 Specification, Version 1.5.0". ftp-osl.osuosl.org. Retrieved 4 March 2021.
  2. ^ "Exif Exchangeable Image File Format, Version 2.2,Sustainability of Digital Formats: Planning for Library of Congress Collections". Retrieved 2020-08-18.
  3. ^ Ahmed, N.; Natarajan, T.; Rao, K. R. (January 1974), "Discrete Cosine Transform", IEEE Transactions on Computers, C-23 (1): 90–93, doi​:​10.1109/T-C.1974.223784
  4. ^ "Standard of the Camera & Imaging Products Association, CIPA DC-008-Translation-2012, Exchangeable image file format for digital still cameras: Exif Version 2.3" (PDF). Retrieved 2014-04-08.
  5. ^ Technical Standardization Committee on AV & IT Storage Systems and Equipment (April 2002). "Exchangeable Image File Format for Digital Still Cameras" (PDF). Version 2.2. Japan Electronics and Information Technology Industries Association. JEITA CP-3451. Retrieved 2008-01-28.
  6. ^ a b "Guidelines for Handling Image Metadata"(PDF). Metadata Working group. 2010-11-01. Archived from the original (PDF) on 2012-01-31. Retrieved 2015-05-11.
  7. ^ "The libexif C EXIF for C". Retrieved 2009-11-08.
  8. ^ "Adobe XMP Toolkit SDK". Adobe Inc.
  9. ^ "Exiv2 Image Metadata Library". Andreas Huggel. Retrieved 2009-02-12.
  10. ^ "Metadata Extractor". Drew Noakes. Retrieved 2011-02-18.
  11. ^ "Image::ExifTool Perl library". Phil Harvey. Retrieved 2009-02-12.
  12. ^ "TIFF Revision 6.0" (PDF). Adobe. 1992-06-03. Archived from the original (PDF) on 2012-07-03. Retrieved 2009-04-07.
  13. ^ "Nikon Tags: Nikon LensData01 Tags". Phil Harvey. 2008-01-25. Retrieved 2008-01-28.
  14. ^ Maximillian Dornseif (2004-12-17). "EXIF Thumbnail in JPEG images". disLEXia 3000 blog. Archived from the original on September 28, 2007. Retrieved 2008-01-28.
  15. ^ "Multi-Picture Format" (PDF). CIPA. 2009-02-04. Archived from the original (PDF) on 2016-04-05. Retrieved 2014-04-29.
  16. ^ "Geotagging with ExifTool". www.sno.phy.queensu.ca​. Retrieved 2019-10-06.
  17. ^ Dpi, misunderstandings and explanation, what is dpi
  18. ^ "McAfee wins stay of deportation from Guatemala". Cnn.com. Retrieved 2012-12-26.
  19. ^ We Are with John McAfee Right Now, Suckers, Vice, December 3, 2012, retrieved 7 December 2012
  20. ^ Alex Wilhelm (December 3, 2012), Vice leaves metadata in photo of John McAfee, pinpointing him to a location in Guatemala, The Next Web, retrieved 7 December 2012
  21. ^ "John McAfee arrested in Guatemala for illegal entry", CBS News, December 5, 2012, retrieved 7 December 2012
  22. ^ Alex Wilhelm (3 December 2012). "In fresh twist, John McAfee now claims he falsified the metadata of the photo that placed him in Guatemala". The Next Web. Retrieved 5 November 2018.
  23. ^ Staff (July 31, 2013). "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'". The Guardian. Retrieved August 6, 2013.
  24. ^ Hassan, Nihad, and Hijazi, Rami. Digital Privacy and Security Using Windows: A Practical Guide. Apress, 2017, pp. 57-59.
  25. ^ "JPEG Rotation and EXIF Orientation / Digital Cameras with Orientation Sensors etc". Impulseadventure.com. Retrieved 2012-12-26.
  26. ^ (JEITA CP-3451) Section 4.7.2: Interoperability Structure of APP2 in Compressed Data.
  27. ^ Phil Harvey (18 March 2011). "FlashPix Tags". Retrieved 29 March 2011.
  28. ^ (JEITA CP-3451) Section 5: Exif Audio File Specification.
  29. ^ Evan Hunter. "EXIF Makernotes - Reference Information". OZHiker. Retrieved 2008-01-29.
  30. ^ "Exif MakerNote 解析カイセキ情報" (in Japanese). Kamisaka. Archived from the original on 2008-12-06. Retrieved 2008-01-29.
  31. ^ "SIGMA and FOVEON EXIF MakerNote Documentation". x3f.info. Archived from the original on 2007-08-05. Retrieved 2008-03-26.
  32. ^ "Makernote Types". exiftool.org.
  33. ^ "Olympus Makernotes" (in German). Olypedia. Archived from the original on 2008-01-19. Retrieved 2008-01-29.
  34. ^ Huggel, Andreas (2012-04-25). "Makernote formats and specifications". Retrieved 2012-09-09.
External links
Wikimedia Commons has media related to Exif.
Last edited on 10 June 2021, at 15:49
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