Commons:Exif

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Photos taken with a digital camera are likely to be JPEG images with embedded Exif data, with automatically recorded date and time the photo was taken, exposure settings, focal length, and so on. You may also directly add Exif information tags to an image, like author and copyright, but using copyright tags is required in Wikimedia Commons nonetheless.

Purpose for using Exif at Commons[edit]

Exif information helps us by keeping all kinds of meta information directly within the file, but it can never replace a good image description. It is displayed by the MediaWiki software in the "Metadata" section at the image description page, and helps make this feature useful.

License information[edit]

Exif information is especially helpful if you don't trust people downloading your media from Commons and reusing it according to your license conditions. Thus, license information is always kept within the Exif of every image copy automatically.

Watermark[edit]

Visible tags or watermarks inside images are strongly discouraged at Wikimedia Commons. Information like "Mr. Foobar, May 2005, CC-BY-SA" should not be written directly in the image but in Exif fields, which is also technically superior. The reasons are:

  • We don't tag our Wikipedia articles prominently with our names in the text of the article, the better to step behind the work and let it speak for itself. The same applies to images, for the same reason that it is crucial for neutrality.
  • Personal tags impede reusing our images, for example in collages and books. As in books, we always have the copyright information in the image caption or at the end of the book and thus a signature in the image would produce redundancy in page layout and be unfair compared to the article author's credit.

Orientation (rotation and mirroring)[edit]

In addition, Exif data can store an "Orientation" tag that specifies if the image needs to be rotated or mirrored for viewing. These are the possible messages in the metadata section on a file page:

Tag value
Meaning
1
Normal
2
Flipped horizontally
3
Rotated 180°
4
Flipped vertically
5
Rotated 90° CCW and flipped vertically
6
Rotated 90° CCW
7
Rotated 90° CW and flipped vertically
8
Rotated 90° CW

Other metadata formats[edit]

MediaWiki can also extract some other non-Exif metadata formats such as IIM or XMP. These are displayed exactly the same way as Exif data. These other formats are not as common as Exif is, but allow a much wider variety of information to be stored. XMP has the particular benefit of allowing metadata to be translated into multiple languages

Format
Type of metadata supported
JPG
Exif, IPTC-IIM (example), XMP, JPEG file comment (COM segment)
PNG
PNG textual tags including support for multilingual iTXt (example), XMP (including Exif and IPTC data if embedded in XMP)
GIF
XMP (Including XMP embedded Exif/IPTC), GIF file comment (example)
OGG
Vorbis comments and Theora comments are extracted but not displayed. It can only be retrieved by the API (example)
SVG
<title> element, <description> element (example). Note: XML metadata from <metadata> element is currently stored but not processed
TIFF
Exif (example)
PDF
Standard "Document Information Dictionary" fields (example), page size, DRM status, and generic XMP fields (PDF specific XMP fields are not currently supported)

Editing Exif fields[edit]

Tools[edit]

  • The Gnu Image Manipulation Program (GIMP) is a free software image manipulation program which can handle Exif data via an Exif viewer plugin.
  • digiKam is a powerful free software image organizer supporting Exif, IPTC and XMP metadata with a visual interface. It also provides an interface for adding GPS coordinates using a map.
  • jhead and ExifTool, that are command line tools helpful for batch editing Exif metadata, and can display and edit XMP, IPTC and Exif and other metadata. ExifTool runs on Unix, Mac OS X and Windows.
  • Mapivi (open source) is a picture manager which is able to add, edit, search and remove image meta information as Exif and IPTC.

GIMP, digiKam, Mapivi and jhead are also available for Mac OSX and Windows.

Linux/Unix users[edit]

  • GIMP is a free software image manipulation program which can handle Exif data via an Exif viewer plugin.
  • Geeqie Image Viewer, an open-source fork of GQView for GNOME, is a graphical program that allows one to view image files and edit Exif metadata. Some key word tags are pre-defined and may be quickly selected with check-boxes, but a free-form text box allows entry of arbitrary key words. Batch processing of collections of images is also possible.

Many free image programs, like the DigiKam digital camera manager and the general purpose image viewer Gwenview (both KDE based), can handle Exif as well. In text console you can use exiv2.

Mac OS X users[edit]

Apple's iPhoto and Aperture can be used to edit title, date, time and keywords. It can view the camera information.

JetPhoto can be used to add GPS data to a photoalbum. JetPhoto uses timestamp information to correlate tracking data from a GPS device with the timestamps on the photo. JetPhoto is freeware so there is no charge but it does not appear to be open source. Keywords, and titles can be edited but no other information.

Reveal can be used to view and edit Exif summary and exposure data.

Windows users[edit]

Programs GeoSetter (freeware) and Konvertor (shareware) are able to edit Exif and IPTC fields such as captions, keywords, etc. Programs XnView (free for non-commercial use), Picasa (freeware) and IrfanView, (free of charge for private use) are able to edit IPTC fields such as captions, keywords, etc. They can view, but not edit, most Exif fields, like Microsoft Pro Photo Tools. BatchPurifier LITE (freeware) can completely erase Exif and other JPEG metadata to protect the user's privacy.

ExifTool how-to[edit]

Using ExifTool, setting copyright and licensing information is simple:

$ ./exiftool -ImageDescription="This is an example image" -Artist="Artist's name" \
-Copyright="This work is licensed under the Creative Commons Attribution 3.0 Unported License. \
To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/ or send a \
letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA." \
-XMP-cc:License="http://creativecommons.org/licenses/by/3.0/" ImageToModify.jpg

This will add three tags: Artist, Copyright, and XMP-cc:License (unported cc-by-3.0 license is used as an example).

Another example:

$ ./exiftool -ImageDescription="1988 company picnic" \
-Artist="Camera owner, John Smith; Photographer, Michael Brown; Image creator, Ken James" \
-Copyright="Copyright, John Smith, 19xx. All rights reserved." Picnic1988.jpg

Note that ImageDescription and Artist are in ASCII format. For 2-byte character sets, UserComment can be used instead of ImageDescription.

To view all tags from Exif group with their current values:

$ ./exiftool -a -exif:all ExampleImage.jpg

Windows users[edit]

Windows XP provides a simple and limited way to modify some Exif fields (refer to [1]). Right click on the image file, select properties, Summary tab. The simple view enables you to edit XPTitle, XPComment, XPAuthor, XPKeywords and XPSubject from the IFD0 group. Note, that XPTitle is ignored by Windows Explorer if ImageDescription exists and XPAuthor if Artist exists. The advanced view displays limited number of other tags, but doesn't allow modification.

The free Microsoft Pro Photo Tools allows additional Exif editing, particularly of geolocation data, while the free Microsoft Photo Info allows extensive editing of IPTC/XMP metadata. Both products are discontinued.

The powerful ExifTool is available as a stand-alone Windows executable that may be used as either a drag-and-drop or a command-line utility. Windows users may also install the Perl version of ExifTool, but this requires that a Perl interpreter (such as ActivePerl) be installed.

Display of geolocating Exif metadata on image description pages[edit]

GPS data will only be shown if one clicks show extended details as it is not on the list of shown by default fields. Additionally, Upload Wizard, Commonist and VicuñaUploader read the data and add template {{Location}} to the page, thus displaying the geographical coordinates and allowing them to be edited. Files uploaded by other means and containing Exif geolocation data are managed by robot "DschwenBot". See also Commons:Geocoding.

Flickr files[edit]

Some Flickr images, when downloaded, lack Exif data due to limitations on free accounts. However, this can be bypassed as follows:

  • Use User:InverseHypercube/flickr_exif.py; or,
  • Copy and paste the Exif data displayed on the Flickr Exif page (Menu "Actions" → "View exif info") to a section on the Wikimedia Commons file page. Afterward, the section on the file page could be deleted and be replaced by a permalink to the old version that contained the Exif data.

Exif data on Commons or in MediaWiki[edit]

For images with Exif data, Exif data are displayed on image description pages (automatic "metadata" section at the end of pages), e.g., at File:T-45A_Goshawk_03.jpg#metadata (picture of the day on 2009-09-27 by Lt. J.G. John A. Ivancic/U.S. Navy)

Exif data are stored in the "img_metadata" field of the "image" table of MediaWiki. For File:T-45A_Goshawk_03.jpg, this looks like the following:

a:25:{s:4:"Make";s:5:"Canon";s:5:"Model";s:21:"Canon PowerShot S5 IS";s:11:"Orientation";i:1;s:11:"XResolution";s:13:"4718592/65536";s:11:"YResolution";s:13:"4718592/65536";s:14:"ResolutionUnit";i:2;s:8:"Software";s:15:"QuickTime 7.4.5";s:8:"DateTime";s:19:"2008:06:05 10:47:30";s:16:"YCbCrPositioning";i:1;s:12:"ExposureTime";s:6:"1/1600";s:7:"FNumber";s:5:"35/10";s:15:"ISOSpeedRatings";i:100;s:11:"ExifVersion";s:4:"0220";s:16:"DateTimeOriginal";s:19:"2008:06:04 12:51:32";s:17:"DateTimeDigitized";s:19:"2008:06:04 12:51:32";s:17:"ShutterSpeedValue";s:6:"341/32";s:13:"ApertureValue";s:6:"116/32";s:17:"ExposureBiasValue";s:3:"0/3";s:16:"MaxApertureValue";s:6:"116/32";s:12:"MeteringMode";i:5;s:5:"Flash";i:16;s:11:"FocalLength";s:10:"26000/1000";s:10:"ColorSpace";i:1;s:13:"SensingMethod";i:2;s:22:"MEDIAWIKI_EXIF_VERSION";i:1;}

The field can be retrieved through database dumps (see User:JovanCormac/UsingDatabaseDumps for a procedure) or through an Application Program Interface (API).

Sample request through API: query for "&prop=imageinfo&iiprop=metadata&iimetadataversion=2"

External resources[edit]