What is EXIF ?
Digital camera save the picture at usually in JPEG. Not just a picture save
at this file, also information from the camera setting while the picture take.
Yes you right, not all digital camera have EXIF, but after EXIF system discover,
almost and maybe all digital camera have funtion to write EXIF data, also the
digital camera could stop the EXIF function to write at file picture.
Exchangeable image file format (Exif) is a specification for the image file
format used by digital cameras. It was written by the Japan Electronic Industry
Development Association (JEIDA). The specification uses existing file formats
such as JPEG, TIFF Rev. 6.0, and RIFF WAVE audio file format, with the addition
of specific metadata tags. It is not supported in JPEG 2000 or PNG. Version
2.1 of the specification is dated June 12, 1998 and version 2.2 is dated April
2002. The metadata tags defined in the Exif standard cover a broad spectrum
including:
- 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,
aperture, shutter speed, focal length, metering mode, and film speed information.
- Location information, which could come from a GPS receiver connected to
the camera. As of 2004 only a few cameras support this, though. Some people
therefore use a normal receiver to track their movements, and then post-process
the images by matching the timestamps in the images with the log from the
receiver and can so add the missing information to images.
- Descriptions and copyright information. Again this is something which is
most often done when post-processing the images, as only high-end camera models
let the user choose a text for these fields. (by Wikipedia)
Example of Exif
Information is like table shown bellow, this information provide by typical
digital camera. Notice that authorship and copyright information is not provided
in the camera's output, so it must be filled in during later stages of processing.
| Tag |
Value |
| Manufacturer |
CASIO |
| Model |
QV-4000 |
| Orientation |
top - left |
| Software |
Ver1.01 |
| Date and Time |
2003:08:11 16:45:32 |
| YCbCr Positioning |
centered |
| Compression |
JPEG compression |
| x-Resolution |
72.00 |
| y-Resolution |
72.00 |
| Resolution Unit |
Inch |
| Exposure Time |
1/659 sec. |
| FNumber |
f/4.0 |
| ExposureProgram |
Normal program |
| Exif Version |
Exif Version 2.1 |
| Date and Time (original) |
2003:08:11 16:45:32 |
| Date and Time (digitized) |
2003:08:11 16:45:32 |
| ComponentsConfiguration |
Y Cb Cr - |
| Compressed Bits per Pixel |
4.01 |
| Exposure Bias |
0.0 |
| MaxApertureValue |
2.00 |
| Metering Mode |
Pattern |
| Flash |
Flash did not fire. |
| Focal Length |
20.1 mm |
| Maker Note |
432 bytes unknown data |
| FlashPixVersion |
FlashPix Version 1.0 |
| Color Space |
sRGB |
| PixelXDimension |
2240 |
| PixelYDimension |
1680 |
| File Source |
DSC |
| InteroperabilityIndex |
R98 |
| InteroperabilityVersion |
(null) |
How to Read EXIF
To view the EXIF information of JPG or TIFF file, you can use many different
software, from native Microsoft Windows viewer, standart picture viewer, until
any brand of software which have a lot of other tools to do with exif also some
software be able to manipulate the EXIF data information.
This is one of many free EXIF manipulator that I like :
http://www.sentex.net/~mwandel/jhead/
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