If a picture is worth 1,000 words, a digital photo is worth 1,001. When you hit the shutter button on your camera it records the light its lens sees, but that’s not all. Each digital photo you take has a variety of data fields embedded inside of it, visible only to those who know exactly where to look.
EXIF is metadata — “data about data”. Each piece of metadata reveals something about your image (and possibly you). The specific kind of metadata recorded inside your digital photos is EXIF, which stands for Exchangeable Image File Format. EXIF data is recorded in a separate portion of your image file than the photographic data, and therefore cannot be seen or detected by looking at the image. Instead, examining EXIF data requires special software to extract and display those fields.
All sorts of data relating to the photograph is stored in EXIF fields. Some of this data includes:
- The camera model.
- Exposure time.
- The lens’ focal length.
- Aperture size.
- Sensor sensitivity.
- Whether or not the flash fired.
- Date & time the picture was taken.
- The type of lens used.
Cameras with GPS, as well as most smart phones record your geographical location at the time you took the photo. Many cameras can also be configured to record your name as the photo’s author.
Individual camera manufacturers such as Nikon and Canon record their own custom EXIF fields on your photos. There are many more fields recorded depending on which camera you use — the ones mentioned here are just the basics.
The landscape photo you see if figure 1 contains EXIF data. Click on it to view the contents in Flickr’s metadata view.
Your camera might not be the only source for EXIF data. Depending on what applications you use to import and process your digital photos, that software might make additions to your photo’s EXIF data fields. For example, importing a photo into iPhoto records the version of Mac OS X you’re using, and “Quicktime” as the software used during import.
Viewing EXIF data requires special software that knows exactly where to look. Here are a few options:
- ExifPro Image Viewer acts like Explorer, but displays all of the EXIF data contained in each photo it finds.
- Exif Reader can extract many of the top camera manufacturer’s formats.
- Windows Explorer: right click the photo, click Properties, then click Summary.
Mac OS X
- Finder: Click on a photo, hold the CMD key and press “I”. Inside the new window that appears, expand the “More Info” section and look for the EXIF data.
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When got my first DSLR and was learning photography, I spent a lot of time looking at the EXIF data of my favorite photographers’ Flickr photos. Being able to see what aperture, shutter speed, and ISO a person chose in difficult lighting situations was an invaluable part of the learning process.
Freaking out over the GPS data recorded in pictures by smart phones is a favorite scare tactic for the media, but I think this feature is great. Travel is the main focus of my own photography, so I like to plot my images in Google Earth. In addition to the geotagged images from my iPhone, I use Canon’s GP-E2 receiver to geotag my 5DIII DSLR’s photos.
EXIF data provides an interesting insight into the art of digital photography. It’s hidden at first sight, but contains a wealth of information about your camera, your settings, and the contents of your picture.