Metadata as defined by the National Information Standard Organization is the structured information which describes, explains, and locates an information resource. In this sense, metadata is the data describing other data and is a key component that ensure the survival and posterity of an information resource. To achieve the survival of crucial information, metadata is divided into two schemes; EXIF and IPTC each designed for specific tasks.
One of the mostly used schemes of metadata is Exchangeable Image File Format (EXIF). EXIF is the digital still-camera (DSC) image format metadata standard that defines metadata using controlled vocabulary and offers detailed information (Tesic 86). Due to increased demand for refined digital camera information and the limitation of DSC to only measure a limited amount of capture information, EXIF is designed to add new tags that record information used by DSC, printers and GPS. Therefore, the scheme supports many DSCs to give many but refined capture information that facilitates easy retrieval and image management by enabling DCs to record capture condition.
The other scheme is the International Press Telecommunication Council (IPTC) which describes and administers photographs to provide a relevant right to information. In describing photographs, IPTC allows for easy access of visual content in human language terms or machine readable codes (Tesic 90). The schema is in three standards which include IPTC core, IPTC extension, and Information Interchange model (IIM).
Originally IPTC was implemented through IPTC to IIM standard that was used to organize, systematize and unify visual information storage and transportation. However, with technological advances two more IPTC schemes; IPTC core and IPTC Extension that focus on news and stock of photos are now available (Ashbrook 21). The three schemas are used together with other software such as Adobe to implement technical metadata which applies Adobe’s XMP technology to format IIM format. Also, users implements IPTC by using IPTC Core and IPTC Extension to comprehensive sets of fields to define metadata properties and to add exert and accurate data about people, place, and products in an image. Other data such as dates, names, and identifiers concerning the capture of the photo and a flexible means of expressing right information are as well implanted by IPTC metadata type.
On the other hand, EXIF is implemented in three standards which include image file direction (IFD), Start of System (SOS), and End of Image (EOI). These standards allows the user to perform administrative metadata processing to give information such as how the image was created, digital camera specifications, location, and lighting conditions. Therefore, EXIF detail the method of recoding the data and their interoperability among imaging devices, commercial software for image processing and cataloging, as well as specialized image-processing software running on computer. The implementation of uncompressed file in TIFF revision 6.0 format and compressed files in JPEG-ISO/IEC 10918-1 format, allow commercial image-processing software to read, view, and process images with embedded EXIF metadata (Ashbrook 20). For example application segments APP1 and APP2 records a compressed EXIF digital image as JPEG file. During the capture of image, every JPEG file starts with start of image (SOI) maker (0*FFD8) being a binary value and ends with end of image (EOI) maker (*FFD9) as the binary value.
- Ashbrook, Stan. “Metadata in Digital Photography; What Is It and How Do I Use It?” Photogarphic Society of America (2009): 19-20.
- Ashbrook, Stan. “Metadata in Digital Photography; What Is It and How Do I Use It?” Photographic Society of America (2009): 20-21.
- Tesic, Jelena. “Metadata practices for consumer photos.” IEEE MultiMedia12.3 (2005): 86-92.