Exchangeable image file format (Exif) is a specification for the imagefile 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.
Exif Print, the latest development of Exif, is an open image file standard defined and controlled by the JEITA organisation.
Exif Print adds new types of data, exposure mode for example, which are specifically important to the digital print process.
Exif Print works simply by storing information important to the print process, such as camera settings (white balance, exposure time, etc) with the image file as each shot is taken.
EXIF is a standard for storing information created by JEIDA (Japan Electronic Industry Development Association) to encourage interoperability between imaging devices.
EXIF data are very useful because you do not need to worry about remembering the settings you used when taking the image.
Example of EXIF 2.2 information extracted with ACDSee 6.0.3 which allows the data preceded by the "pencil" icon to be edited.
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