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Classes of Metadata

Different types or classes of text information about digital files, called metadata, serve specific purposes.

Some classes of metadata can be - and are - embedded in digital image files. Some schemas, or data formats, actually identify their elements by these classes, although this may not be readily apparent. Each of the followig three “classes” of metadata become part of the image file when embedded in JPEG, TIFF, PSD, Raw or several other popular formats. They can also be stored in a sidecar file.

Technical Metadata
Most modern image-capture devices generate information about themselves and the pictures they record, such as that stored in Exif. These data describe an image’s technical characteristics, such as its size, color profile, ISO speed and other camera settings. Some professional cameras can be configured to add detailed ownership and descriptive information in a note or comment field stored within the Exif container.

Descriptive Metadata
A photographer or image collection manager can enter and embed various information about an image’s contents. This can include captions, headlines, titles, keywords, location of capture, etc. These metadata fields were included in the original IPTC-IIM schema. They have been expanded in the IPTC Core and IPTC Extension metadata schemas. Good descriptive metadata are key to unlocking an image collection to find stored images.

Administrative Metadata
Image files can also include licensing or rights usage terms, specific restrictions on using an image, model releases, provenance information, such as the identity of the creator, and contact information for the rights holder or licensor. These types of metadata have been comprehensively addressed and standardized within the PLUS sytem. The IPTC Core and IPTC Extension schemas also expand on the types and quantity of such information metadata can store.