Lightroom uses a catalog to track the location
of files and remember information about them. A catalog is like
a database that contains a record of your photos. This record is
stored in the catalog and contains data such as preview information,
links that indicate where the photos are located on your computer, metadata
that describes the photos, and editing instructions applied in the Develop
module. When you rate photos, add metadata and keyword tags, organize
photos into collections, or remove photos from the catalog—even when
the original photo files are offline—the settings are stored in
the catalog.
All of this information enables Lightroom to give you flexibility
in managing, identifying, and organizing photos. If you’re photographing
on location, for example, you can import photos into Lightroom on
your laptop, and then move the original photos onto writable media
or storage devices, and continue organizing and managing your photos
without worrying about filling up the laptop hard drive. You can
then transfer the catalog to your desktop computer, preserving the
changes you make and keeping track of where the photos are stored.
The catalog that you import with photos from the on-location shoot would
be a separate catalog from any other catalog that may be stored
on the desktop computer.
Note: Although you can view photos in both Lightroom and Adobe Bridge,
the two applications behave differently. To view photos in Adobe
Bridge, your hard drive must contain the photos, or your computer
must be connected to a storage media that contains the photos. This
is because Adobe Bridge is a file browser that only displays readily
accessible photos. The Lightroom catalog is a database that keeps
track of the photos you import, so you can preview photos whether
your hard drive contains the actual photos or not. To edit photos
in Lightroom, however, the software does need to be able to access
the stored photos.
By default, Lightroom loads the most recent catalog. You can
open a different catalog by choosing File > Open Catalog,
or you can determine which catalog is opened in the General preferences.
For more information on Lightroom catalogs, see Catalog
FAQ | Lightroom.
