Exif Version 2.2 - Exchangeable image file format for digital still cameras which is based on Standard of Japan Electronics and Information Technology Industries Association JEITA CP-3451.

The Exif image file specification stipulates the method of recording image data in files, and specifies the following tems:

Structure of image data files,
Tags used by this standard,
Definition and management of format versions.

Features of the Exif image file is based on existing The file-recording formats. Compressed files are recorded as JPEG (ISO/IEC 10918-1) with application marker segments (APP1 and APP2) inserted. Uncompressed files are recorded in TIFF Rev. 6.0 format. The use of existing formats means files recorded using a DSC or related system can be read directly by commercial applications, and makes possible the use of functions for viewing and manipulating the images.

Definition of Glossary:

"Tag" is used as a synonym of "field".
".H" appended to a numerical value means it is hexadecimal notation, Unless otherwise indicated, other numerical values are given in decimal notation.
The initial IFD in a file is the "0th IFD," with the next IFD being called the 1st IFD.
Number of Pixels of the primary image when it is recorded as either uncompressed or JPEGcompressed data. Note that when recording as JPEG compressed data images for which the number of lines (ImageLength) or number of samples/line (ImageWidth) is not a multiple of 8 or 16.
Pixel Composition and Sampling - The combination of pixel composition and pixel sampling for image data shall be RGB 4:4:4 and either Y:Cb:Cr =4:2:2 or Y:Cb:Cr = 4:2:0. The pixel composition of image data shall also be 8 bits each. This specification is applied similarly to thumbnails.As sampling points on the elements making up pixels, the Y and Cb,Cr sampling points may be either co-sited.
DSC stands for Digital Still Camera.