What format is EXIF?

Exif is the abbreviation of English exchangeable image file, originally formulated by JEIDA- Japan Electronics Industry Development Association, and the latest version is 2.2 1. The camera file design standard (DCF- the design role of camera file system) being formulated by ISO may be based on Exif2. 1.

Exif file is actually a kind of JPEG file, which follows the JPEG standard, except that shooting information and index map are added to the header information of the file. Therefore, you can use any image tool software that supports JPEG format to view or modify the Exif file, but you may not see the Exif information when you open it. Once modified, Exif information may be lost.

Simply put, EXIF information is a series of information collected by digital cameras during shooting, and then placed at the head of the well-known JPEG/TIFF file. That is to say, EXIF information is a set of shooting parameters embedded in JPEG/TIFF image file format, which mainly includes various information related to shooting conditions at that time, such as aperture, shutter, ISO, date and time, camera brand model, color coding, sound recorded during shooting and global positioning system (GPS). Simply put, it is like the date printing function of a fool's camera, except that the information recorded in EXIF information is more detailed and complete.

EXIF 21.pdf (580K) JEIDA) EXIF 2. 1 official standard formulated by JEIDA. ( 1998.6. 12)

The official standard EXIF 2.2(750k) formulated by JEIDA in Exif22.pdf. (2002.4)

EXIF file format describes an EXIF English reference file written by a Japanese, and the content is very detailed.

Identification of Exif

All JPEG files start with the string "0xFFD8" and end with the string "0xFFD9". There are a series of "0xFF" strings called "ID" in the file header, which are used to mark the information segments of JPEG files. "0xFFD8" indicates the beginning of image information, and "0xFFD9" indicates the end of image information. There is no information behind these two signs, and there are some information characters behind other signs.

The identifiers between 0xFFE0 and 0xXFFEF are called "application tags", which are not used in traditional JPEG files. Exif uses these information strings to record shooting information, such as shutter speed, aperture value and even global positioning information. According to the definition of these identifiers in Exif2. 1 standard, digital cameras can record various shooting information in digital images, and application software can read these data, and then retrieve their specific meanings according to Exif2. 1 standard, which generally includes the following information:

Image description image description, source. Refers to a tool for generating images.

Artists and authors have some cameras that can input user names.

The manufacturer refers to the product manufacturer.

Model refers to the equipment model.

Some cameras support orientation while others do not.

X resolution/yre resolution X/Y direction resolution There is a special entry in this column to explain this problem.

Resolution unit Resolution unit is generally PPI.

Software software displays firmware firmware version.

Date time date and time

Ycbcr positioning hue positioning

ExifOffsetExif information location, defines the writing method of Exif information in the file, and some software does not display it.

Exposure time exposure time is the shutter speed.

F $ numerical aperture coefficient

ExposureProgram Exposure program refers to the setting of programmed automatic exposure, which varies from camera to camera, and may be Sutter priority, aperture priority and so on.

ISO speed rating sensitivity

ExifVersionExif version

Date Time Original Creation Time

Date and time digitized time

Component Configuration Image Construction (Multi-Finger Coloring Scheme)

When CompressedBitsPerPixel(BPP) is compressed, the color bit of each pixel refers to the degree of compression.

Exposure compensation value.

Max aperture of MaxApertureValue

Photometric mode Photometric mode, average photometry, central button photometry, spot photometry, etc.

Light source light refers to the white balance setting.

Whether Flash uses flash.

FocalLength generally shows the physical focal length of a lens, and some software can define a coefficient to show the focal length of a 35mm camera. MakerNote (user comments) is marked, explained and recorded by the author.

FlashPixVersionFlashPix version (supported by individual models)

Color space gamut, color space

ExifImageWidth Image width refers to the number of horizontal pixels.

The existing image height refers to the number of vertical pixels.

The definition pointer of interoperability IFD universal extension is related to TIFF file, and its specific meaning is unknown.

Source file compression ratio.