Commons:EXIF

Photos taken with a digital camera are likely to be a JPEG image, with embedded EXIF data. So they will have the date and time the photo was taken, and some information about the exposure, focal length etc. You can also add EXIF information to an image in order to directly tag your images with additional informations like author and copyright information if you like (but using Commons:Copyright tags is required in Wikimedia Commons nonetheless in all cases).

Purpose for using EXIF at Commons

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

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

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.

See also: Commons:Watermarks

Orientation (rotation / mirroring)

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

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

See also: Commons:Rotation

Editing EXIF-fields

Tools

• 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 & 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 meta data, 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

GIMP is available for Linux/Unix.

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

MacOSX users

Apple's iPhoto 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

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. BatchPurifier LITE (freeware) can completely erase EXIF and other JPEG metadata to protect the user's privacy.

HOWTO

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

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 which 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

File description pages don't display geolocating metadata (see bugzilla:13172). However, images containing EXIF geolocation data are being managed by robot "DschwenBot", which adds template {{Location}} to the page, thus displaying the geographical coordinates and allowing them to be edited. See also Commons:Geocoding.

Exif data on Commons/in Mediawiki

For images with exif data, exif data is 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/US Navy)

EXIF data is 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 API.

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

External Resources

• exif.org - Specification of EXIF and documentation.
• http://www.controlledvocabulary.com/imagedatabases/iptc_naa.html - More info on the history of IPTC, as well as a list of programs for editing IPTC fields.
• http://graphicssoft.about.com/od/exifsoftware/ - A list of software able editing EXIF tags.
• http://regex.info/exif.cgi Online Exif Data Viewer