Metadata is not a setting or mode that you'll find on your camera, but your camera is generating lots of metadata every time you take a picture. To use a simple definition, metadata is information about information. More specifically, metadata is structured information about a collection of data—such as an image file—that makes accessing and using that file more efficient and productive.
Advances in the digital management of information have underscored the importance of metadata among different professional disciplines, but the concept has been around for a long time. Distance scales, notations, and legends on maps, for example, qualify as metadata since they are essentially information about the map, which in itself is just information about a specific geographic area (Figure 4.24). Dictionaries also feature metadata in the form of a dictionary guide that tells you how to interpret the different information you'll find listed in the word definitions.
Figure 4.24 This explanatory note on a nautical chart is metadata that provides further information about the symbols and markings found on the chart.
For digital photographers, the metadata associated with image files represents important information about their photos that can be a very useful tool to aid in the management and organization of an image collection. Metadata allows you to sort and filter photos by a variety of criteria and, if you're taking advantage of the ability to add descriptive keywords to your files (which we strongly recommend), it can help you easily and quickly find specific images. The more information associated with an image file, especially in the form of keywords, the more potential value that file has—not just possible monetary value (though that is certainly an important aspect of putting metadata to work for you), but also the simple value that comes from being able to locate an image you're looking for. Though it may not be as exciting as a new lens, metadata is just as important as any other piece of gear in a photographer's camera bag.
For most digital cameras, metadata consists of a record of the settings that were in effect when an image was photographed. This information typically includes data such as the date and time the image was created, pixel resolution, shutter speed, aperture, focal length, ISO, white balance, metering pattern, and whether the flash was used. The information is saved using a standard format called Exchangeable Image File (EXIF).
At the most basic level, EXIF data can be a useful tool to help you improve your photographic technique. Because it keeps track of basic exposure information, you can study it to learn what the settings were on photos that worked and on images that had problems. For example, if you notice that several images from a session are slightly out of focus and others have sharp, clear details, a quick check of the EXIF data for the soft images might reveal that the camera used a slower shutter speed for them than it did with the sharp photos (see the sidebar "Accessing Camera EXIF Data"). This knowledge can help you make different exposure decisions the next time you're shooting in similar conditions.
Records of exposure information may be useful, but that's only the beginning of many possible uses for metadata. As mentioned previously you can also add descriptive keywords to facilitate faster searching and retrieval from an image database. Other uses for metadata include adding your contact and copyright information to all your images (many programs allow you to do this as the files are downloaded to your computer); adding captions, location details, and GPS coordinates, as well as specific client and job information; and tracking image usage for photographers who license their photos. For further discussion on adding keywords in Lightroom, see Chapter 8.