Commons:EXIF
From Wikimedia Commons, the free media repository
Photos taken with a digital camera are likely to be a JPEG image, with embedded EXIF data. So they willl 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).
Contents |
[edit] Purpose for using EXIF at Commons
EXIF information is always helpful in order to keep all kinds of meta information directly within the file (but it can never replace a good image description) and as it gets displayed by the MediaWiki software at the image description page in the "Metadata" section it is a good idea making this feature useful.
EXIF information is especially helpful if you don't trust people downloading your media from Commons and reusing it according to your license conditions. So license information is always kept within every image copy automatically.
Visible tags or watermarks inside images are strongly discouraged at Wikimedia Commons. So 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 with our names in a prominent way inside the article text in order to step behind the work and let it speak for itself, the same applies to the images (stepping behind own work and thus reducing personal vanity is crucial for neutrality).
- Reusage of images with these signatures for example for printing purpose gets limited by personal tags like at collage posters and in books (as in books you always have the copyright information in the image caption or at the end of the book and thus it would produce unprofessional duplications in page layout and would also be unfair compared to the article author's credit).
[edit] Editing EXIF-fields
[edit] Tools
The Gnu Image Manipulation Program (GIMP) is the chief Free Software image manipulation program which can handle EXIF data via an EXIF viewer plugin.
There are also several command line tools that are for example helpful for batch editing EXIF meta data like jhead and ExifTool, that 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, Mapivi and jhead are also available for Mac OSX and Windows.
[edit] 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.
[edit] MacOSX users
Apple's iPhoto can be used to edit title, date, time and keywords. The camera information can also be viewed.
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.
[edit] Windows users
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., but unluckily can only view most of EXIF fields. Else Exifer (postcardware) Konvertor (shareware) is capable as well editing and modifying the EXIF header.
[edit] 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
[edit] 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.
There is also a free tool from Microsoft called Microsoft Photo Info [2] that allows extensive editing of IPTC/XMP metadata.
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.
[edit] Display of geolocating EXIF metadata on image description pages
Presently, image description pages unfortunately fail from displaying geolocating metadata. This is a known problem reported on https://bugzilla.wikimedia.org/show_bug.cgi?id=13172 .
However, images containing EXIF geolocation data are being managed by robot "DschwenBot", which adds the geolocating coordinates by inclusion of template {{Location}} on the image description page. See also : Commons:Geocoding.
[edit] 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"
[edit] 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.
