EXIF stands for Exchange Image File Format. This is a standard that is set by the Japan Electronic Industry Development Association. This standard is used for storing informational data into an image file. This standard is used in the major image formats used by digital camera manufacturers to allow for interoperability between imaging devices. The full specifications are available at http://www.exif.org.
Most digital cameras use Exif compressed file formats like JPEG. Following the JPEG specification allows for the image data to be read by any software that supports the JPEG format, like web browsers, image editing software and desktop presentation software. In addition to the image, the Exif compressed files also store metadata. This metadata is available to your software and it can be used as a photo log (of sorts) to describe camera settings used in the images that you've taken.
Below is the Exif metadata available from a Nikon Coolpix 995 image as viewed in Image Studio 5 from ArcSoft (free with many Nikon cameras). Please note, this data is not always available to all software products and may not be recorded by all cameras:
|Exif Version=0210||Shot Time=2002:07:04 16:02:43|
|Digitize Time=2002:07:04 16:02:43||Compress Rate=4.0 bits/pixel|
|Exposure Time=10Second||F Number=2.6|
|Minimum F Number=||Focal Length=8.20 mm|
|X Resolution=||Y Resolution=|
|ISO Speed Rate=ISO100||Flash=No Flash|
|Light Source=Auto||Exposure Program=Normal|
|Color space=sRGB||Image Width=2048|
|Image Length=1536||User Comment=|
|Related audio file=||Optoelectric conversion factor=|
|Maximum lens aperture=0.00||Subject distance=|
|Metering mode=Pattern||Flash energy=|
|Spatial frequency response=||Subject location=|
|Exposure index=||Sensing method=|
|File source=||Scene type=|
As you can see from the information above, not all pieces of information were written by the camera and it follows Exif format 2.1, not the most recent version 2.2. The information available here is important to you if you are going to want to increase your skills as a photographer because it will allow you to not use a notebook to write down every piece of information about every picture that you take. More importantly, it will allow you to get to the point where you can use something other than the 'Auto' functions on your camera.
For much more information about the information available, click here.
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