Exif
Exchangeable image file format (Exif) is a standard for storing metadata in image and audio files.
The Exif specification defines limited subsets of TIFF, JPEG, and WAV formats, and adds a standard way to store metadata in such files. Although it may be technically inaccurate, it's natural to think of Exif as the metadata format that is embedded in such files (instead of the files as a whole). And in practice, Exif metadata is sometimes used in files that do not conform to the specification, or in file formats that are not in the specification.
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Embedding
For TIFF format, Exif defines a number of new TIFF tags, which are integrated into the TIFF file in IFDs that are pointed to by TIFF tags 34665, 34853, and 40965.
In JPEG (and other image?) files, Exif data is stored in what amounts to an embedded TIFF file. The data is structurally valid TIFF data, though it would not make a fully valid TIFF file because it does not have a primary image. An APP1 marker with the identifier "Exif" is used for Exif data.
The Exif specification also defines a way to store FlashPix data in Exif-conformant JPEG files. APP2 markers with the identifier "FPXR" are used. This uses a completely different data format, unrelated to TIFF.
Identifiers
| Format | PRONOM | LoCFDD |
|---|---|---|
| Exif 2.2 | fdd000146 | |
| Exif 2.2 JPEG | x-fmt/391 | fdd000147 |
| Exif 2.2 TIFF | x-fmt/387 | fdd000145 |
| Exif 2.2 WAVE | x-fmt/396 | |
| Exif 2.1 JPEG | x-fmt/390 | |
| Exif 2.1 TIFF | x-fmt/388 | |
| Exif 2.1 WAVE | x-fmt/389 | |
| Exif 2.0 JPEG | x-fmt/398 | |
| Exif 2.0 TIFF | x-fmt/399 | |
| Exif 2.0 WAVE | x-fmt/397 |
