Every single JPG photo file your digital camera saves contains a lot of information about how the photo was taken. This data is known as Exif data, shorthand for Exchangeable image file format.
Exif data includes image size, plus actual shooting aperture, speed and ISO setting. In addition, it contains the focal length of the lens used, color space data, measuring and shooting mode as well as the make and model of the camera, right down to the serial number!
If your camera has an onboard GPS, your Exif data also “knows” exactly where on the planet each individual photo was taken, enabling you to use software such as iPhoto, Picasa or Lightroom to geotag your images.
Exif data is also very useful anytime you want to archive your photos in chronological order. Of course this only works if you make sure and set your camera to the correct date and time right out of the box. You should also remember to set your camera to the proper time zone when you travel, otherwise you might wonder how you got that beautiful shot of a sunset at 2 in the afternoon!
Specialized sites such as (www.stolencamerafinder.com/) allow you to attempt tracing a stolen camera based on the Exif data from online photos. Chances are if someone uses a stolen camera and publishes photos online, the Exif data just might allow you to trace the camera to whoever is using it.
Understand why you missed
Beginners can learn a lot from Exif data. It works like the “black box” on an airliner. It makes it easy for an instructor or a more experienced photographer to point out what may have gone wrong in trying to capture a given shot.
As you progress, it also makes it easier to compare photos taken at various speeds, apertures and ISO settings, and to understand how each of these factors affect your final image. You can be sure the data in each file is absolutely right.
On most computers, you can use the CTRL + I or cmd + I keystroke to display the data, or, from your Finder or Windows desktop, use the View/Settings/Details menu. Most post-processing software will display the data in a range of customizable display options.
The more you know about what happened in the camera, the more chances you have of knowing exactly what to do the next time you’re inspired to capture what you see.