Metadata is a set of standardized information about
a photo, such as the author’s name, resolution, color space, copyright,
and keywords applied to it. For example, most digital cameras attach
some basic information about a file, such as height, width, file
format, and the time the image was taken. Lightroom also supports
the information standard developed by the International Press Telecommunications
Council (IPTC) to identify transmitted text and images. This standard
includes entries for descriptions, keywords, categories, credits,
and origins. You can use metadata to streamline your workflow and
organize your files.
File information is stored using the Extensible Metadata Platform
(XMP) standard. XMP is built on XML. In the case of camera raw files
that have a proprietary file format, XMP isn’t written into the
original files. To avoid file corruption, XMP metadata is stored
in a separate file called a sidecar file. For all other
file formats supported by Lightroom (JPEG, TIFF, PSD, and DNG),
XMP metadata is written into the files in the location specified
for that data. XMP facilitates the exchange of metadata between
Adobe applications and across publishing workflows. For example,
you can save metadata from one file as a template, and then import
the metadata into other files.
Metadata that is stored in other formats, such as EXIF, IPTC
(IIM), and TIFF, is synchronized and described with XMP so that
it can be more easily viewed and managed.