Have you wondered how Flickr publishes the most popular cameras in their community? How does Flickr get the information about camera model, such as Nokia Sony Ericsson W810i or Nokia N73?

Top Popular Cameraphones on Yahoo! Flickr

The answer to the questions above is Exif. According to Wikipedia:

Exchangeable image file format (official abbreviation Exif, not EXIF) is a specification for the image file format used by digital cameras…. The specification uses the existing JPEG, TIFF Rev. 6.0, and RIFF WAVE file formats, with the addition of specific metadata tags. It is not supported in JPEG 2000 or PNG.

Basically, Exif is metadata embedded into images captured with digital cameras, including camera phones. Not only camera model, Exif stores many other parameters, such as focal length, exposure time, aperture value and many more.

How can we view Exif information? Many photo management software, such as Google’s Picasa, and image viewer software, such as IrfanView (with additional plug-in), are able to display Exif information. The following screenshot shows Exif information from a picture taken with Nokia N73. Just for your information, I use IrfanView to display Exif information.

Displaying Exif information on IrfanView