EXIF

EXIF or the Exchangeable Image File Format is a standard produced by the Japan Electronics and Information Technology Industries Association. The standard specifies the formats to be used for images, sound and tags in digital still cameras and in other systems handling the image and sound files recorded by digital still cameras. The data embedded generally relates to the physical attributes of the image (e.g. width, height, whether a flash was used, camera shutter speed, F stop used, etc.) rather than attributes about the subject of the image (e.g. keywords, location, etc.). As such, EXIF metadata is closely tied to the master image as it describes the physical attributes of that image.

EXIF information is embedded in an image using the TIFF 6.0 tags specification. Each EXIF property (that is a setting value, like Flash Fired - indicating whether the flash was used) is described by two numbers. The first number, called the IFD (Image File Directory) represents the broad area within which the property resides. EXIF provides five possible IFDs:

  1. Primary Image IFD (Primary)
  2. EXIF specific IFD (Exif)
  3. GPS (Global Positioning System) IFD (GPS)
  4. Interoperability IFD (Interopability)
  5. Thumbnail IFD (Thumbnail)

Each IFD has its own set of numbers that represent specific attributes within that IFD; each number is known as a tag. For example, the EXIF IFD has a tag number 36867 that contains the date and time the picture was taken. By combining the IFD and the tag we get a unique identifier for a metadata value. The value 2:36867 represents the 2nd IFD (EXIF specific) with tag 36867 (date and time picture was taken). The IFD:Tag notation is used by EMu to specify EXIF metadata values.

The tables below describe the possible tags for each IFD. For a complete description of the values available for a given attribute, please consult the EXIF Version 2.2 standard.