Exchangeable image file format
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Exchangeable image file format (Exif) is a specification for the image file format used by digital cameras. It was written by the Japan Electronic Industry Development Association (JEIDA). The specification uses existing file formats such as JPEG, TIFF Rev. 6.0 and RIFF WAVE audio file format, with the addition of specific metadata tags.
Version 2.1 of the specification is dated June 12, 1998 and version 2.2 is dated April 2002.
The metadata tags defined in the Exif standard cover a broad spectrum including:
- Date and time information. Digital cameras will record the current date and time and save this in the metadata.
- Camera settings. This includes static information such as the camera model and make, and information that varies with each image such as orientation, aperture, shutter speed, focal length, metering mode, and film speed information.
- Location information, which could come from a GPS receiver connected to the camera. As of 2004 only a few cameras support this, though. Some people therefore use a normal receiver to track their movements, and then post-process the images by matching the timestamps in the images with the log from the receiver and can so add the missing information to images.
- Descriptions and copyright information. Again this is something which is most often done when post-processing the images, as only high-end camera models let the user choose a text for these fields.
Holding on to the Exif Metadata
Since the metadata is embedded in the file, one has to be careful when editing Exif files. The problem is that some older programs know nothing about Exif data, and so they won't preserve it when saving an image. This means that a simple operation such as rotating the image might end up removing the Exif metadata.
As more and more programs become aware of Exif metadata the situation improves, but as of 2004 one still has to look out for old programs.
See also
- Camera File System
- Digital photography
- Image processing
- DIG35
- XMP
- Geocoded Photo
- Graphics file format
- IPTC
External links
- EXIF.org (http://exif.org/)
- Exif in the TIFF Tags Directory (http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif.html)
- Citations from CiteSeer (http://citeseer.org/cs?q=Exchangeable+image+file+format+EXIF)
- Digital Image File Formats (http://www.i3a.org/links_digital-image-formats.html)
Manipulation (read/write support):
- Opanda PowerExif Editor (http://www.opanda.com/en/pe/)
- Jhead (http://www.sentex.net/~mwandel/jhead/) (C)
- OpenExif Toolkit (http://openexif.sourceforge.net/) (C++)
- Picture Metadata Toolkit (http://picturemetadata.sourceforge.net/) (C++)
- EXIF Tag Parsing Library (http://sourceforge.net/projects/libexif) (C)
- PEL: PHP Exif Library (http://pel.sourceforge.net/) (PHP)
- ExifTool Perl module (http://www.sno.phy.queensu.ca/~phil/exiftool/)
Extraction (read support):
- Opanda IExif viewer (http://www.opanda.com/en/iexif/)
- ImageMagick™ (http://www.imagemagick.org/)
- Exif JPEG camera setting parser and thumbnail remover (http://www.sentex.net/~mwandel/jhead/)
- Python Exif Parser (http://pyexif.sourceforge.net/)
- PHP function: exif_read_data() (http://www.php.net/manual/en/function.exif-read-data.php)
- exiftags (http://johnst.org/sw/exiftags/)
- Image::EXIF (http://search.cpan.org/~ccpro/Image-EXIF/) perl module, wrapper to exiftags (above)
- EasyExif (http://www.one-nine.com/downloads.aspx)
- IrfranView (http://www.irfanview.com/)
Display:
- Opanda IExif for Windows folder & Internet Explorer (http://www.opanda.com/en/iexif/)
- Opanda IExif for Mozilla Firefox (http://www.opanda.com/en/iexif/firefox.htm)
- Exif-Viewer (http://www.amarra.de/exif_uk.htm)
- Simple EXIF Viewer for Mac OS X (http://homepage.mac.com/aozer/EV/)
- EXIF Image Viewer (http://home.pacbell.net/michal_k/exif_v.html)
- Digital Camera Extended File Information Viewer (http://www.oneilsoftware.com/Exif/Exif.html)
- Exifer for Windows (http://www.friedemann-schmidt.com/software/exifer/)
- Exif Browser (http://www.software-factory.ch/software/exifbrowser/exifbrowser_down_en.htm)
- TTNview (http://myalpha.dls.net/ttnview/)de:Exchangeable Image File Format