Digital Photography Technology

Medadata is information embedded in every file when a picture is taken with a digital camera. Depending on the manufacturer of the camera, it gives all the information as to how the photo was taken, plus other additional information. Below is a description taken from Wikipedia about the exchangeable image file format.

Background

Exif was created by the Japan Electronic Industries Development Association (JEIDA). Version 2.1 of the specification is dated June 12, 1998, and the latest, version 2.3 dated April 2010, was jointly formulated by JEITA and CIPA. Though the specification is not currently maintained by any industry or standards oganization, its use by camera manufacturers is nearly universal.

The metadata tags defined in the Exif standard cover a broad spectrum:

• 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 (rotation), aperture, shutter speed, focal length, metering mode and ISO Speed information.
• A thumbnail for previewing the picture on the camera’s LCD screen, in file managers, or in photo manipulation software.
• Descriptions and copyright information.

Technical

The Exif tag structure is borrowed from TIFF files. On several image specific properties, there is a large overlap between the tags defined in the TIFF, Exif, TIFF/EP, and DCF standards. For descriptive metadata, there is an overlap between Exif and  IPTC

info, which also can be embedded in a JPEG file.

When Exif is employed for JPEG files, the Exif data is stored in one of JPEG’s defined utility Application Segments, the APP1 (segment marker 0xFFE1), which in effect holds an entire TIFF file within. When Exif is employed in TIFF files (also when used as “an embedded TIFF file” mentioned earlier), the TIFF Private Tag 0×8769 defines a sub-Image File Directory (IFD) that holds the Exif specified TIFF Tags. In addition, Exif also defines a Global Positioning System sub-IFD using the TIFF Private Tag 0×8825, holding location information, and an “Interoperability IFD” specified within the Exif sub-IFD, using the Exif tag 0xA005.

This information is extremely useful for every photographer to help analyze a photo after it has been taken. It can not be deleted and helps to identify the photo forever.