Image metadata is text information pertaining to an image file that is embedded into the file or contained in a separate file that is associated with it.
Image metadata includes details relevant to the image itself as well as information about its production. Some metadata is generated automatically by the the device capturing the image. Additional metadata may be added manually and edited through dedicated software or general image editing software such as GIMP or Adobe Photoshop. Metadata can also be added directly on some digital cameras.
Image metadata can be very useful for cataloging and contextualizing visual information. Many visual artists find the features useful in providing data about themselves and their images.
Image metadata can also help protect intellectual property. It is important to note, however, that copyright information is not adequate protection as it can easily be stripped away. Also, as with other types of content, metadata security can be cumbersome, requiring extra measures to secure image metadata and protect it from unauthorized access.
The three main categories of image metadata are:
Technical metadata is mostly automatically generated by the camera. It includes camera details and settings such as aperture, shutter speed, ISO number, focal depth, dots per inch (DPI). Other automatically generated metadata include the camera brand and model, the date and time when the image was created and the GPS location where it was created.
Descriptive metadata is mostly added manually through imaging software by the photographer or someone managing the image. It includes the name of the image creator, keywords related to the image, captions, titles and comments, among many other possibilities. Effective descriptive metadata is what makes images more easily searchable.
Administrative metadata is mostly added manually. It includes usage and licensing rights, restrictions on reuse, contact information for the owner of the image.
Several standardized formats of metadata exist, including: Information Interchange Model (IPTC), Extensible Metadata Platform (XMP), EXchangable Image File (Exif), Dublin Core Metadata Initiative (DCMI) and Picture Licensing Universal System (PLUS).