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The International Press Telecommunications Council (IPTC) was established in 1965 to safeguard the telecommunications interests of the world press.  Since the 1970s, the organization has focused on developing and publishing industry standards for the interchange of news data. Since 1979, photographer know IPTC for creating the set of metadata attributes applied to images. The organization has remained a key player in the development of metadata.

For many years, newspapers and other news outlets received photos via an early facsimile machine. The photo, including caption and other information, were placed on a revolving drum and transmitted over telephone lines.

In 1988 Leaf, Inc. released the Leaf Desk, designed by Bob Caspe. The Leaf Desk was one of the earliest units designed for transmission of images from the field.  It consisted of a scanning stage that accommodated a three image strip of 35 mm film, a keyboard for writing captions, a modem and a small computer screen.  Since the Leaf Desk had no digital memory device, the whole scanning, captioning and transmission process was repeated each time the same image was sent to another destination.

Some of the earliest discussions about metadata as we know it today occurred just prior to the introduction of the Leaf Desk. During a National Press Photographers Association digital show in San Francisco, photo editor Stephen Hart of the Associated Press, Senior AP Photo Editor Grant Lamos and AP Photo Editor Pete Leabo discussed the problems of sending images and cutline information in a Chinatown bar.  They realized that whatever protocol they adopted would have to dovetail with current procedures.  A year or two later at Hurley's bar in Manhattan Hart met with AP Photo Library Director Chuck Zoeller and David Rocha, also of AP, to discuss the coming of the Leaf Desk.  Though there were some guidelines from the American Newspaper Publishers Association (now known as the Newspaper Association of America), these may have been two of the earliest discussions of photo metadata fields.

Not long after introduction of the Leaf Desk came the Spooler, an external hard drive that let photographers scan and save images before transmission. As such, photographers could scan several images, then send them as a group.

Manually writing metadata into each and every image file can be a tedious job, which was why  Mike Evans, formerly President Ronald Reagan's photographer, started Iron Mike Software to facilitate embedding metadate into Adobe's Photoshop 95.  Though the Iron Mike approach was useful, there were incompatibilities because Adobe and Iron Mike wrote the data differently. Leaf Desk would pick up metadata from either Adobe or Iron Mike software.  But, if one wrote the data using Iron Mike and then did something in Photoshop, the Adobe program would not recognize the Iron Mike annotations and, in turn, Leaf Desk would find no information in the metadata file.  Still, AP shooters  liked Iron Mike software because it could write simultaneously to a batch of images, which Photoshop could not. Apple Computer also got involved in the early days of metadata when it introduced a low-end digital camera bundled with imaging software that accepted Photoshop plug-ins, including Iron Mike.  About this time, AP created Photo Lynx, a photo browser for Apple's Macintosh computers with a docking station that offered Leaf transmission functions.

IPTC developed the Information Interchange Model (IIM) in 1990.  IMM provides specifications for metadata fields. Though it  was never intended specifically for use with photos, Adobe adopted the standard in 1995 when it chose 20 photo metadata fields from the IIM to be included in Photoshop. The IMM schema was updated in 1999. In 1997 Adobe Systems, Inc., standardized on the use of the Image Resource Block (IRB) method of storing metadata, which adds different kinds of image data –– including, but not limited to metadata –– to a digital picture.

Photo metadata took a conceptual leap forward in 1994 when Adobe outlined the specifications for embedding the information into a digital Image Resource Block (IRB), often  called IPTC headers.  Adobe chose 20 fields for use in Photoshop 95. Though this was a bit limited by today's standards, the ability to embed information into JPEG and TIFF images was the basis of the image management system that exists today.

In 2001 Adobe introduced the Extensible Metadata Platform (XMP), a successor to the Image Resource Blocks. XMP represents the same types of metadata as IPTC, but uses Extensible Markup Language (XML), which is coded instructions about displaying text, and  Resource Description Framework (RDF), a simplified general-purpose digital language for representing information. Says Adobe: "With an XMP-enabled application, information about a project can be captured during the content-creation process and embedded within the file and into a content-management system. Meaningful descriptions and titles, searchable keywords, and up-to-date author and copyright information can be captured in a format that is easily understood by you as well as by software applications, hardware devices, and even file formats."

In 2005 Adobe released its Creative Suite 2, which included the new IPTC Core. IPTC core was the result of an IPTC/Adobe collaboration.  It includes and defines most IIM fields previously adopted by Adobe. New fields were added including new subject, scene and intellectual genre codes.  Two additions to the geographic information let photographers record places smaller than a city and areas outside municipalities as well as codes for countries. The IPTC Core panels were backwards compatible and could be used in the CS version of Photoshop as well, however, this did require that the user manually install the panels.

A revision to the IPTC Core was released in 2008 along with a new IPTC Extension schema. The IPTC Extension 1.0 Schema complements and extends the set of IPTC Core metadata properties, to include additional fields that are shared with the PLUS schema, such as model and property release info, as well as more detailed location information and much more.

Currently, all digital cameras embed Exchangeable Image File Format (Exif) technical metadata about the creation of an image. Exif data includes information such as the camera's make, model and serial number; the date and time the image was made; shutter speed; ISO; and the lens used. Established in 1985 by the  Japanese Camera Industry Association, the predecessor to the Camera & Imaging Products Association, Exif is also used by some image scanners. RAW camera processing software can use Exif information to accurately render images. New technologies such as Exif Print incorporate photographic information into printing processes for improved results. Today, the Japan Electronics and Information Technology Industries Association manages the Exif standard.

Timeline of IPTC and related Metadata Standards:

1979: IPTC defines a set of metadata attributes.
1991: IPTC revises attributes, releases new version dubbed the “Information Interchange Model” or IIM.
1994-95: Adobe Photoshop adopts Image Resource Block (IRB) / IPTC Headers.
2001: Adobe launches the Extensible Metadata Platform or XMP.
2005: IPTC/Adobe collaboration releases IPTC Core in Creative Suite 2.
2007: IPTC and IFRA hold first International Photo Metadata Conference and release white paper.
2008: IPTC releases revised IPTC Core and new IPTC Extension schemas.

History of the Exif (Exchangeable Image File Format) Standard

October 1995: Version 1 established as a JEIDA standard. Defined the structure, consisting of an image data format and attribute information (tags), and basic tags.
November 1997: Version 1.1 kept the essential provisions of Version 1.0 and added provisions for optional attribute information and format operation.
June 1998: Version 2 added sRGB color space, compressed thumbnails and audio files.
December 1998: Version 2.1 Upgraded and expanded the storage format and attribute information. Added recommended compatibility details as a supplement to Version 2.0
February 2002: Version 2.2 added information to Version 2.1 to improve print finishing
September 2003: Version 2.21 added optional color space (Adobe RGB)
Source: Hiroshi Maeno, Canon Inc. June, 7, 2007, First International Photo Metadata Conference, Florence, Italy.

If you have other metadata-related terms to add, contact us.

INDEX
A-C
D-G
H-J
K-M
N-Q
R-T
U-Z

ANSI - Abbreviation for the American National Standards Institute (ANSI), a private non-profit organization founded in 1916 that oversees the development and accreditation of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.  These standards ensure that the characteristics and performance of products are consistent, that people use the same definitions and terms, and that products are tested the same way.

Administrative Metadata -  Information such as licensing, usage rights or restrictions, model releases, provenance, and contact information for the rights holder or licensor, rather than descriptive information about the photo.

Archive Master - See Master.

ASCII - Abbreviation for the American Standard Code for Information Interchange. ASCII, was one of the early (1960) character encoding methods based on the English alphabet. It was used in representing text in computers, communications equipment and other devices that work with text. Other modern character encodings, such as UTF-8, support many more characters, but have a historical basis in ASCII.

Bit - A contraction of binary digit, the smallest unit of information storage or digital information that can take on one of two values, such as false and true or 0 and 1.

Byte - A component in the machine data hierarchy usually larger than a bit and smaller than a word; now most often eight bits and the smallest addressable unit of storage. A Byte typically holds one character.

Capture - The process by which a digital image is acquired as a digital file, either by a digital camera or by digitally scanning with analog material (film / prints).

Cataloging - The process of adding images and both administrative and descriptive information about them, either automatically or manually, to an image database, or digital asset management system.

Checksum - A checksum is a fixed-size datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during its transmissions or storage.   The checksum is transmitted or stored along with the data; the receiving system recomputes the checksum based upon the received data and compares this value with the one sent with the data. If the two values are the same, the receiver has some confidence that the data was received correctly.

Comp - A shorthand reference to a "comprehensive" or visual rendering of a proposed advertisement or other printed piece. These would usually indicate the intended placement of each photograph, illustration and/or text. Images made available for these purpose are often referred by this term.

Compression - Process of coding digital data using fewer bits, in order to save storage space or transmission time.  There are many Compression algorithms and utilities. The most common file format for photos  transmission is JPEG (q.v.) which provides several degrees of compression, each of which loses some bits of data.

Container - In the digital imaging world, these are semantic objects used to group together or store related information to be easily referenced. For example, all of the Exif metadata is stored in one container within the header of an image file.

Container format - Container or wrapper formats, such as DNG, may group RAW image data and metadata together into a single object, making it a meta-format, because both the real data as well as the information about the data format are stored within the file itself.

Controlled Vocabulary - Controlled vocabularies ensure that the same terms are used for the same concepts and objects in a database, with similar and related terms clearly defined.  Used in the construction of thesauri and taxonomies, they effectively limit choice by offering pre-selected terms from which users must choose.

Corruption - See Data Corruption.

CSV - An abbreviation for "Comma Separated Value", a type of delimited text file format (q.v.) in which a comma separates the columns in which tabular data is stored. It dates back to early business computing methods, and is common to all computer platforms.

Crosswalk - See "metadata crosswalk."

Cutline - An older term used in the newspaper industry to indicate the caption to be used with a published photograph or illustration.

Data Corruption - The errors that occur to a data file or digital image as it is transferred or retrieved, which introduce unintended changes to the original data. With some errors it is possible to recover or partially recover the file. In some cases the pixel data may be preserved, but the information in the file header such as Exif or IPTC metadata may be lost.

Data File - See File.

Data Integrity - The assurance that data is accurate, correct and valid. With computer systems it is possible to verify data integrity by checking hash values, checksums, or other means.

Decompression - To reverse the effects of data compression.

Decryption - Any procedure used in cryptography to convert ciphertext (encrypted data) into plaintext. (From FOLDOC:http://foldoc.org/?query=Decryption).

Delimited file format - A plain text file format in which the various elements of a sequential file have their columns separated from one another using a specific recurring character, such as the comma or tab. Each row represents one record, and the delimited value keeps the data in ordered columns. Delimited files are useful in getting data from one program into another program. Tab delimited text files, and Comma Separated Value (CSV) files are both examples of delimited file formats.

Derivative File - Used for image files that are created from an original or archive master file by subsampling or oversampling. Thumbnail or preview images that allow users to see what an asset looks like before they open the larger file are all examples of derivative files. They may also refer to images that will be used for production purposes but where some aspect has been altered such as the resolution, format type, or color space. The term derivative files can almost be used interchangeably with surrogate files, though derivatives imply a wider range of uses.

Descriptive Metadata - Information which tells the viewer what or who is in the image, and where and when the image was taken. These include captions, headlines, titles, keywords, location, date created and more.

Diacritic - Precomposed letters containing special marks used in digital typography to indicate a special pronunciation, such as the accent, cedilla, grave, tilde, and umlaut (áçèîñõü). These letters many not be represented in the most basic character sets and thus may not be transcribed correctly when exchanging photo metadata between operating systems.

Diacritical mark - See diacritic.

Digital Asset Management - Digital Asset Management (DAM) refers to the methods of employing some form of database management of both images and their corresponding metadata to support accurate storage and retrieval of digital graphics and image files.

Digital Migration - See Migration.

Digital Object - A discrete unit of information in digital form such as a digital image file, or other document format such as PDF, Powerpoint, etc.

Digital Rights Management - The use of encryption or other technological means to regulate access to a licensable digital work, such as images, songs, movies, other software or sensitive documents.

Digital Negative (DNG) - Abbreviation for the Adobe Digital Negative Format. A wrapper technology or Container Format for holding RAW files along with other associated information such as metadata in XMP format. They can also be used to hold previews of images and a wide range of other data which can be stored with an image rather than in Sidecar Files (q.v.).

Digitization - Digitization is the process of converting analog film or physical prints (or other items) into digital equivalents. There are many methods that can be used. Film can be scanned with a dedicated film scanner or flatbed, prints or book pages can be scanned on a flatbed or photographed with a digital camera. The need to digitize will likely diminish with the move to direct digital capture.

Disc - Typically round optical storage device such as a CD or DVD.

Disk - A physical hard drive on which data is stored. Also referred to as a drive.

Downsampling - Resampling a digital image downwards by discarding pixel information, thus reducing the pixel density (resolution) and/or image dimensions.

Dublin Core Metadata Initiative (DCMI) - The Dublin Core Metadata Initiative (DCMI) is the name of the organization that first established this metadata standard. Because Dublin Core fields can, in theory, be applied to almost any type of asset, not simply photos it has become more popular within the  public sector as well as other archives and digital repositories. The original version was a standardised core set of 15 fields or criteria for broadly describing content. DCMI data can be placed in-line in the meta tags of web pages (or as a reference to an associated XML file) as well as for other content such as photos, documents, videos etc.

Encryption - Any procedure used in cryptography to convert plaintext into ciphertext (encrypted message) in order to prevent any but the intended recipient from reading that data. Schematically, there are two classes of encryption primitives: public-key cryptography and private-key cryptography; they are generally used complementarily. Public-key encryption algorithms include RSA; private-key algorithms include the obsolescent Data Encryption Standard, the Advanced Encryption Standard, as well as RC4.

Excel - A Microsoft spreadsheet format used to hold a variety of data in tables which can be sorted, calculated, or graphically displayed.

Exif - A metadata schema used to store technical metadata typically coming from a digital camera.This provides a host of information, such as the camera make and model, its serial number, the date and time of image capture, the shutter speed, lens used, the ISO speed setting, and often other technical details, such as white balance and distance to the subject. RAW file processing software can use Exif information to more accurately render images.

FPO - Abbreviation used to indicate low resolution images that are to be used "For Position Only" in comps.

File - A named and ordered sequence of Bytes that is known and understood by an operating system. A File can be zero or more Bytes, has permissions assigned (read/write/remove), and has file system statistics such as size and last modification date. A File also has a Format.

File Header - The non-image portion of a digital image file, preceding or following the actual pixel data, which contains information about the file such as those contained in various types of technical, descriptive and administrative metadata typically written using the EXIF, IPTC or XMP standards.

Format - A preexisting structure specifying the organization of a File, such as TIFF, JPEG, etc.

Header - See File Header.

Homonym - Words that are pronounced or spelled the same way but have different meanings.

ICC Color Profile - These are embedded metadata labels, developed by the International Color Consortium to indicate the color space used to create and edit the file. It is best to always embed an ICC profile in a digital image so that the colors as intended by the file creator are correctly transmitted, received, and viewed by the file recipient.

IIM - The abbreviation for the Information Interchange Module, the schema outlining the first IPTC metadata standard that was used in formulating the original File Info for Photoshop.

Ingest - The process by which one or many captured digital image files are taken into a computer system for some form of digital asset management.

Interoperability - The ability to exchange and use information between various systems or schemas.

IPTC Core - A metadata schema developed by the International Press Telecommunications Council that updated the previous IPTC schema to work with the newer Adobe XMP metadata standard. This IPTC4XMP format stores information separate from the IIM form of IPTC metadata but shares many fields that are backwards compatible to a degree. Also referred to as the IPTC4XMP, or IPTC Core Schema for XMP, it comprised the fields included in the IPTC Contact, Image, Content and Status panels that appear under the File> File Info menu in Photoshop.

IPTC - A metadata schema based on the Information Interchange Module (IIM) and named for the group that developed it in 1991, the International Press Telecommunications Council. A portion of the IIM was incorporated into Photoshop in 1995 and is stored in an Image Resource Block (IRB). While considered a legacy format, it remains widely used and readable by most software that accesses metadata.

IRB - Abbreviation for the Image Resource Block, a method of encoding non-pixel text-based information into the header of a digital image file.

JFIF - The technical name for the file format better known as JPEG. Typically only used when it is crucial to communicate the difference between the JPEG file format and the JPEG image compression algorithm.

JPEG - Is an acronym for the original name of the committee, (Joint Photographic Experts Group), that designed the standard image compression algorithm. As an 8-bit per channel format used for compressing either full-colour or grey-scale digital images of "natural", real-world scenes, JPEG does not work as well on non-realistic images (cartoons, line drawings, maps).

JPEG 2000 - JPEG 2000 is a wavelet-based image compression standard developed by the Joint Photographic Experts Group and with the intention of superseding their original discrete cosine transform-based JPEG standard (created in 1992). The standardized filename extension is .jp2 or .jpx.As of 2008, there is little support for JPEG 2000 in web browsers, and hence it is not used much for image display on the Internet, though it has been adopted for use by a number of cultural heritage institutions.

KML - KML is an abbreviation for Keyhole Markup Language (KML) an XML-based language used to describe three-dimensional geospatial data for display in application programs. KML was originally developed by Keyhole, Inc, (acquired by Google in 2004) for use with what became Google Earth. The term "Keyhole" is a reference to the KH reconnaissance satellites, the eye-in-the-sky military reconnaissance system launched in 1976.

KMZ - These are simply zipped KML files which use a .kmz file extension. When a KMZ file is unzipped, a single "doc.kml" is found along with any overlay and icon images referenced in the KML.

kb - See Kilobyte.

Kilobyte - A measure of file size and storage capacity which refers to 1,000 or 1,024, 8-bit data units or characters, depending on context.

LAMP - Acronym for applications, such as a number of open source image databases,  that use Linux, Apache, MySQL, and PHP (LAMP)to operate on the Internet.

LOC - An abbreviation for the Library of Congress.

LZW - Abbreviation for Lempel-Ziv Welch compression, the algorithm designed by Terry Welch in 1984 for use in high-performance disk controller hardware and used by the Unix compress command to reduce the size of files for archiving or transmission. The LZW algorithm relies on the recurrence of byte sequences (strings) in its input, and is a popular compression type for use with TIFF files.

MB - See Megabyte.

Master - The finished, fully-developed version of a digital or analog image, used as the source for making various derivative files.

Megabyte - A measure of file size and storage capacity which refers to 1,048,576, 8-bit data units or characters; or 1024 kilobytes. 1024 megabytes equals one gigabyte.

Metadata - Data about Data, in terms of Digital Photo Management, text data that informs you about the subject matter in a way that is more useful than noting that it is a collection of colored pixels.

Metadata Crosswalk - Metadata crosswalks show people how to match up the data from one scheme into a different scheme. They are often used by libraries, archives, museums, and other cultural institutions to translate data to or from specific metadata schemes.   This type of "translating" from one format to another is often called "metadata mapping" or "field mapping," and is related to "data mapping," and "semantic mapping."  Metadata crosswalks also help databases using different metadata schemes to share information. They help metadata harvesters create union catalogs. They enable search engines to search multiple databases simultaneously with a single query.

Metadata mapping - See "Metadata Crosswalk."

Metalogging - The process of adding descriptive information (metadata) about an image and storing it in such a way that it can be used as an aid in retrieving that image from a database or collection after it is “cataloged.”

Migration - The process of moving digital information from one form of storage to another, which may or may not involve transforming the file format as well.

NAA - Abbreviation for the Newspaper Association of American, one of the groups responsible, along with the IPTC, for establishing early photo metadata standards.

Namespace - A namespace is an abstract container, also called context,  created to hold a logical grouping of unique identifiers or symbols (i.e., names), in order to differentiate them from items in different namespaces that have the same name, and prevent any ambiguity between them.  Storage devices use directories (or folders) as namespaces, for example. This allows two files with the same name to be stored on the device so long as they are stored in different directories.   Computer languages that support namespaces specify the rules that determine to which namespace an identifier (i.e., not its definition) belongs.  The Adobe XMP labeling technology that allows you to embed metadata into an image file, uses namespaces associated with a Uniform Resource Identifer (URI) (q.v.) that identifies the namespace, so that each of the field names within that namespace are unique. Namespaces such as those used by Adobe or PLUS can be found at ns.adobe.com, or ns.useplus.org.

Ontology - In the context of Digital Asset Management, an ontology shows the relationships, properties and functions between terms or concepts which can express a wider range of relationships between attributes or terms than can a simple hierarchy. This can be very useful when attempting to represent complex or multi-faceted relationships.

Original - First or master version of a digital or analog image. See also, Master.

PDF - Abbreviation for the Adobe Portable Document Format, the native file format for Adobe Systems' Acrobat. This file format represents documents in a way where they are independent of the original application software, hardware, and operating system used to create them.

Photo-CD - A format popularized by Kodak, for scanning analog film and storing it in an "image pac" format.

Plaintext - The normal representation of textual data before any action has been taken to conceal or format it. Within image metadata circles, this usually refers to text file formats in which there are no formatting codes such as bold, italic, underline, point size, or font designations.

PLUS - The Picture Licensing Universal System is an integrated set of standards for communicating rights metadata associated with commissioned and stock images. The PLUS standards are developed, approved and maintained by the PLUS Coalition, an international, non-profit umbrella association representing publishers, designers, advertising agencies, photographers, illustrators, stock image distributors, artist representatives, museums, libraries, and standards bodies, such as UPDIG, IPTC, IDEAlliance and others. More information at  http://www.useplus.org.

PNG - Abbreviation for Portable Network Graphics, a format for storing bitmapped images, employing lossless data compression and supporting transparency. PNG was created to replace the GIF format as its use does not require a patent license.

Preview image - Refers to the larger on-screen version of an image, the next size up from a thumbnail, and may be smaller than a comp or FPO. A preview image is typically accessed by clicking on the thumbnail in an image database.

Proxy Files - Proxy files are those derived from an original digital master and are typically used (in combination with metadata) to assist users in locating images in a database. Proxy files include previews and thumbnails files and may also be referred to as Derivative Files.

PSB - The .PSB (Photoshop Big) format is an updated version of .PSD specifically designed for dealing with files over 2 gigabytes in size.

PSD - The .psd (Photoshop Document) format is a popular proprietary file format from Adobe Systems, Inc. It has support for most all of the imaging options available in Photoshop, such as layer masks, transparency, text, and alpha channels. In addition, spot colors, clipping paths and even duotone settings can be saved if you are preparing images for printing.

RAW - A RAW image file is a variety of image file that contains unprocessed (or minimally processed) data from the image sensor of a digital camera or image scanner, without processing them into a more common image format such as JPEG or TIFF. Raw files require additional processing by a raw converter in a wide-gamut colorspace before conversion to format where they are ready to be used with a bitmap image editor or printed. Because the characteristics of each RAW format change depending on which vendor or manufacturer, this makes dealing with them using Digital Image Management tools quite complex. Because original RAW files are quite fragile and may be corrupted with the use of third party software, many applications, such as Adobe Photoshop, Lightroom and Bridge, use sidecar files to store the changes made to them. As a result, Adobe developed the DNG (Digital Negative) format to the RAW file and attendant metadata in a single Container Format.

Record - A set of data (typically field of information) relating to am individual item in an image database.

Render - To present a Digital Object to a user by converting the high-level object-based description into a graphical representation in order to display the image.

Resample - Resampling an image changes its resolution through interpolation, making calculations using already known values.

RGB - An abbreviation for the colors Red, Green, and Blue used to display color on many projected light devices such as computer monitors, televisions and video projectors.  ICC color standards are used to define the display accurately.

Rights - Assertions of one or more rights or permissions pertaining to a Digital Image and/or what a specific Agent or Distributor can do with an Image.

Rights Management - The processes associated with active control and management of the licensing history of a work.

Rights Metadata - A subset of Administrative Metadata which identifies the creator, copyright holder, or licensor, and defines which rights are being granted or reserved.

Schema - A formal structural description or model of the various fields that are contained in a database or database-like structures, such as XML files. Both the Exif and IPTC Core are examples of schemas.

Sidecar files - Sidecar files are a method of storing data (often metadata) related to a file in an external file, rather than embedding it into the source file. Each source file can have one or more sidecar files, whereas a "metadata database" the one database contains metadata for several source files.  In most cases  sidecar files have the same base name as the source file, but with a different extension. The problem with this system is that most operating systems and file managers have no knowledge of these relationships, and might allow the user to rename or move one of the files thereby breaking the relationship.   For file formats that have no internal support for XMP data, the data is stored in separate .xmp files with the same base file name. Many photo cataloging applications have support for this file format.

slug; slug-line - Newspaper editing lingo for a short name given to an article that is in production. When metalogging you can put the name of the event into the Headline field within the IPTC metadata of an image.

SQL - An abbreviation for Structured Query Language, a standard interactive and programming  language used for defining and manipulating tables of data in a relational database management system.

Steganography - A term of Greek origin, meaning "covered" or "hidden writing." which refers to methods of concealing a message or word within a digital image so that a viewer does not  realize it is there.  Signum Systems and Digimarc have created techniques for embedding a hidden watermark or copyright data in digital images as a method of protecting creators' or owners' rights to its intellectual property.

Storage - The act or process of storing information in some form of non-volatile computer memory such as magnetic tape or disk, or optical disk (CD-R, DVD-R).

Store - The act of writing a data or image file to some non-volatile storage device such as a hard drive, tape, CD-R or DVD-R.

Suffix - One or more letters added at the end of a filename prior to the extension, which gives clues as to the specific type of image file. For example, a file with the suffix 'r' indicates that it is the RGB version of the image.

Surrogate File - see Proxy files.

Synonym - A word, phrase, or term that has a meaning the same as, or very near to, that of another word, phrase or term.

Tab Delimited - A type of delimited text file which uses the tab character to separate each of the columns used for storing tabular data. This form of storing data is popular with many databases making it a popular way to exchange data between programs.

Tag - The act of attaching a label, such as a keyword, to a digital photo or other image resource.

Taxonomy(ies) - A type of classification which implies a hierarchical system (i.e. it has parent/child relationships between terms).

Technical Metadata - For most modern image-capture devices this is information which describes an image’s characteristics, such as its size, color profile, ISO speed and other camera settings.

TGM-I - Abbreviation for the Thesaurus of Graphic Materials- I (cross reference for indexing visual materials).

TGM-II - Abbreviation for the Thesaurus of Graphic Materials- II (Genre and Physical Characteristic Terms).

Thesaurus -  A classified list of terms, such as key-words, and including synonyms (and sometimes antonyms) for the words of a given language.or used in a particular field, typically used for indexing and information retrieval.

Thumbnail image - A miniature version of an image that is smaller than a preview, and typically used in an image database, or on a web page to represent or provide a link to other content, such as a larger version of the image.

TIFF (or tif) - Tagged Image File Format images are stored using a proprietary method currently owned by Adobe.

UCS - An abbreviation for Universal Character Set, also a component of the abbreviation UTF, which stands for USC Transformation Format.

Unicode - A series of character encoding standards intended to support the characters used by a large number of the world’s languages designed for use internationally in computers. Unlike the 8-bit ASCII encoding scheme which can only represent 256 characters, Unicode characters are 16-bit, which allows for 65,536 combinations, enabling it to encode the letters of all written languages as well as thousands of characters in languages such as Japanese and Chinese.

Upsampling - Another way to refer to resampling a digital image upwards which requires creating pixel information based on the adjacent values.

URI, URL, URN - Uniform Resource Identifier (URI) consists of a string of characters used to identify or name a resource on the Internet, which enables interaction with representations of the resource over a network, typically the World Wide Web.  Computer scientists may classify a URI as a locator (URL), or a name (URN), or both.  A Uniform Resource Name (URN) functions like a person's name, while a Uniform Resource Locator (URL) resembles that person's street address. The ISBN system for uniquely identifying books provides a typical example of the use of typical URNs.

USM - Abbreviation for UnSharp Masking, a means of creating additional definition in the edge transition areas of an image in order to retain detail.

UTF - An abbreviation for USC Transformation Format; which describe one of a set of standard character encodings such as UTF-8 and UTF-16 which are created in accordance with ISO 10646, although the Unicode standard includes additional material.

UTF-16 - An abbreviation for the UCS transformation format 16 text encoding. This is a Unicode character set, encoded with a 16-bit transformation method as defined in RFC 2279.

UTF-8 - An abbreviation for UCS transformation format 8  text encoding; a Unicode character set, encoded with an 8-bit transformation method. This format avoids the problems of fixed-length Unicode encodings because an ASCII file encoded in UTF is exactly same as the original ASCII file; and any non-ASCII characters have the most significant bit set, so that normal tools for text searching etc. work as expected.

Validation - The process of checking or evaluating a Digital Image to ensure that it complies with the requirements of a standard or benchmark. For example, the structure of a Digital File can be validated against a file format specification to test for data corruption.

Verification - See Validation.

Volume - A logical or virtual entity that consists of portions of one or more hard drive disks. A volume may be formatted and may have a file system, a drive letter, or both. A volume is expressed by a type and a layout (simple, spanned, striped, RAID 1, etc.).

Watermark - A term adapted from the printing industry, which involves superimposing a recognizable image, pattern, or words so that the parts of the image it covers appear lighter or darker that the rest of the image. Watermarks are often used to assert ownership or copyright management information.

Workflow - A  logical sequence of steps taken or tasks performed that define the paths taken to complete a task with a specified outcome, subject to certain approvals or tests. It may be illustrated with a flowchart to define specific actions, results, decisions, or desired outcomes.  In photography, refers to the sequence of actions from capture to output that produce a final image.

XMP - An abbreviation for Extensible Metadata Platform a specific type of extensible markup language used to store metadata in digital photos. XMP was introduced by Adobe in 2001. Adobe, IPTC and IDEAlliance collaborated to introduce in 2004 the IPTC Core Schema for XMP, which transfers metadata values from IPTC headers to the more modern and flexible XMP.

We've arranged this reference library according to the following Index, leading with a short list
of "recommended reading." If you have other metadata-related resources to recommend, contact us
and we'd be glad to add them to this resource.

INDEX
Recommended Reading
Introductory Basics
Metadata Viewing and Manipulation Utilities
Standards, Specifications and Schemas
Guidelines and Best Practices in Metadata Applications for Images and Image Collections
Image Metadata Discussion Forums
Metadata Conference Presentations & Reports
Periodical Articles
Blogs
Reference and Lookup Tools
Additional Copyright Resources

Recommended Reading

Start with this selected group of articles that provide a good introduction, then dig deeper below for more insight.

User Guide to the IPTC Core
Descriptions of how to correctly put the current IPTC fields to use to embed metadata in digital files.

A Short History of the IPTC (International Press Telecommunication Council) Standards
by David Riecks
An excellent beginners' outline that also answers most frequently asked questions.

Basic Metadata: A Photographer's Best Friend
by Ethan G. Salwen, ASMP Bulletin, Fall 2007

Basic Metadata: Don't Process Without It
Adding Contact and Copyright Metadata to Your RAW Processing Workflow
by Ethan G. Salwen, AfterCapture magazine, Oct/Nov 2007
Addressing practicing photographers, Salwen advocates adding metadata to RAW images as a first step in    processing, using templates for key metadata.

UPDIG: Universal Photographic Digital Imaging Guidelines, version 4.0
September 2008
The UPDIG guidelines aim to establish photographic standards and practices for photographers, designers, printers, and image distributors. They cover Digital Asset Management, Color Profiling, Metadata, and Photography Workflow.  Separate Guidelines for Photographers and Image Receivers are available on this site.

Introductory Basics

These sources provide an introduction to the problem of image data and metadata interchange, and early steps toward the solution.

A Short History of the IPTC (International Press Telecommunication Council) Standards
David Riecks, [n.d.]
An excellent beginners' outline that also answers most frequently asked questions.

SAA's Metadata Manifesto, issued July 2006
This site provides both a web version and a downloadable PDF outlining a proposal from the Stock Artists Alliance for the adoption of guiding principles, standards and technology to promote image metadata use among image-using industries around the world.

IPTC Photo Metadata White Paper 2007, Document Revision 11
Outlines metadata properties vital to image interchange, and workflows in current use by various types of image creators and users.

Basic Metadata: A Photographer's Best Friend
by Ethan G. Salwen
ASMP Bulletin, fall 2007

Software supporting IPTC photo metadata standards IIM and "IPTC Core"
A vendor submitted list maintained by the International Press Telecommunication Council (IPTC) of various software applications with information on which of the IPTC metadata standards are supported.

IPTC Tests Software Tools to Embed and Read Rights Data
Free and Inexpensive Software tested by the IPTC Photo Metadata Working Group for the ability to write specific embedded photo metadata.

How to Extract Image Metadata Using Python
A tutorial on how to extract various forms of metadata embedded in a PNG file using the programming language, Python. 

Metadata Viewing and Manipulation Utilities

Utilities for Viewing

Jeffrey Friedl's Online Metadata Viewer
A web based utility for reading Exif, XMP, IPTC, ICC, etc., data in most file types (including JPEG, TIFF, PSD, RAW, NEF, CR2, MP3, WMV, etc.) whether remote or local.  Includes a button that can be dragged and dropped into one's local browser button bar (Compatible with recent versions of the Firefox and Safari browsers).  The most flexible image metadata web-based viewer now available.

FxIF (Firefox exIF) is a browser Add-on for Firefox which allows you to read Exif, IPTC-IIM (the older IPTC binary format), and XMP metadata. After installing, you simply right click on an image and choose this option, and the metadata will be shown in a separate window.

Metapicz is an online metadata and exif viewer for digital photos. You can drag and drop an image that is on a desktop computer, or point to an image on the web by URL to see the embedded XMP and Exif metadata. It does not seem to properly recognize any field containing an array (of which the IPTC Core and IPTC Extension contain a few). It also does not seem to recognize the older IPTC-IIM form of photo metadata.

ExifTool GUI for Windows v4
[released April 4, 2010]
View Exif, IPTC, XMP, Maker Notes and more. This utility takes Phil Harvey's command line ExifTool utility and gives it a Graphical User Interface. Instructions for use can be downloaded as a ZIP file at http://u88.n24.queensu.ca/~bogdan/etgui_manual.zip

Exif Viewer 1.45
A Firefox addon, by Alan Raskin.  Displays the Exif and IPTC data in local and remote JPEG (only) images.

XMP metadata extractor (Jpeg only)

A web based utility for extracting the XMP from a JPEG file whether remote or local.

The FotoForensics site has tutorials and links to software and other resources, explaining how to find and extract metadata in photos.

Utilities for Manipulating Metadata

ExifTool
ExifTool is a platform-independent Perl library plus a command-line application for reading, writing and editing meta information in image, audio and video files. ExifTool supports many different types of metadata including EXIF, IPTC, XMP, and many others. ExifTool is also available as a stand-alone Windows executable and a Macintosh OS X package.

The IPTC Cultural Heritage Panel for Adobe Bridge
This link to a ZIP file includes two plugin panels for Adobe Bridge CC (up to 2016 versions) and CS5/CS6 with a focus on fields in the IPTC Photo Metadata Standard 2016 relevant for images of artwork and other cultural heritage objects like buildings. These panels support:

• Reading and writing the complete set of Artwork or Object fields of the IPTC standard
• Key image administration fields
• Automatically generating image caption and keywords from existing Artwork or Object data
• The second panel allows for import and export of data into IPTC fields embedded into an image

Meta Shot Put
Meta Shot Put is a free image importer app for powerpoint that automates the placing of a batch of images (versions for Mac and Windows exist). If you have more than about 5 or 10 images it will save you a lot of time and hassle.

Standards, Specifications and Schemas

Photo Image File Format Specifications

JPEG
JPEG File Interchange Format, version 1.02
Issued September 1, 1992

TIFF
TIFF Revision 6.0
Final, June 1992
Adobe developers' file standards for TIFF file type.

PSD
File Standards for Photoshop PSD file type.
Updated May 2008
Parts copyrighted by Thomas Knoll

Photo Metadata Standards & Specification Schemas

Dublin Core
Dublin Core Metadata Element Set, Version 1.1
A ready reference to all Dublin Core elements;  includes references to controlled vocabularies available for individual elements.

DCMI Metadata Terms
Dublin Core Metadata Initiative
Recommendation of the DCMI Usage Board, issued January 2008.

IPTC Core
"IPTC Core" Schema for XMP, version 1.0
Specification Document, revision 8
IPTC 2005.
XMP value types and schema properties are given here, as well as a list of deprecated legacy IIM metadata elements mapped to current XMP values.

XMP
XMP (Extensible Metadata Platform)

XMP: Adding Intelligence to Media
XMP Specification
Adobe, 2005
Data and storage models, schemas, and embedding in image files.

IPTC Photo Metadata Standards
General Overview
IPTC Photo Metadata Standard 2016 (PDF)
IPTC Photo Metadata Standard 2014 (PDF)
IPTC Photo Metadata Standard 2010 (PDF)
IPTC Photo Metadata Standard 2008 (PDF)
IPTC Core, Specification Version 1.1
IPTC Extension, Specification 1.0
IPTC-NAA Information Interchange Model (IIM), version 4, Rev 1, July 1999
Standard for representing and exchanging news information (both text and image).

Exif
JEITA  Exchangeable image file format for digital still cameras: Exif Version 2.2
JEITA CP-3451, established April 2002.
Published by Japan Electronics and Information Technology Industries Association (JEITA)
English translation of the standard, though the Japanese original is authoritative.

JEITA 49-1998
JEITA 49-1998 is the earlier version of the Exif standard.

PLUS Coalition License Data
PLUS (Picture Licensing Universal System)
Free registration required to access the standards information, which includes:

BETA version of the PLUS License Generator, a web based tool that generates a PLUS Universal License Summary file in XMP, suitable for embedding in digital image files. The License Generator is available in the "UsePLUS" menu of the PLUS website for free.

BETA version of a License Embedder and Reader (different versions for Mac and PC), that allows users to embed or read a Universal License Statement one file at a time. Future versions will support batch processing, saved license templates, saved user contact info.

For Digital Image Collections

XML
NISO Metadata for Images in XML Schema
Technical metadata for digital still images standard
The Library of Congress' Network Development and MARC Standards Office, in partnership with the NISO Technical Metadata for Digital Still Images Standards Committee and other interested experts, is developing an XML schema for a set of technical data elements required to manage digital image collections.

ANSI/NISO Z39.87 - Data Dictionary - Technical Metadata for Digital Still Images
Defines a set of metadata elements for raster digital images to enable users to develop, exchange, and interpret digital image files. The dictionary has been designed to facilitate interoperability between systems, services, and software as well as to support the long-term management of and continuing access to digital image collections.

VRA Core 4.0
Visual Resource Association, Data Standards Committee, March 2007.
This is a data standard for the cultural heritage community, providing a categorical organization for the description of works of visual culture as well as the images that document them. It consists of a metadata element set as well as an initial blueprint for how those elements can be hierarchically structured.

World Wide Web Standards and Specifications

W3C Resource Description Framework (RDF)
RDF Vocabulary Description Language 1.0: RDF Schema
W3C Recommendation 10 February 2004
The Resource Description Framework (RDF) is a general-purpose language for representing information in the Web. This specification describes how to use RDF to describe RDF vocabularies. This specification defines a vocabulary for this purpose and defines other built-in RDF vocabulary initially specified in the RDF Model and Syntax Specification.

Encoding Dublin Core metadata in HTML
Informational Memorandum, not a standard.  Offers several examples of encoding.
IETF, December 1999.  © The Internet Society.

Image Annotation on the Semantic Web
W3C Incubator Group Report 14 August 2007
Offers use cases and solutions that illustrate vocabularies used in Dublin Core and VRA Core data elements.

Date and Time (W3C)
This document defines a profile of ISO 8601, the International Standard for the representation of dates and times. ISO 8601 describes a large number of date/time formats. To reduce the scope for error and the complexity of software, it is useful to restrict the supported formats to a small number. This profile defines a few date/time formats, likely to satisfy most requirements.

Guidelines and Best Practices in Metadata Applications
for Images and Image Collections

User's Guide to the IPTC Core and IPTC Extension (for Photoshop CS5)
(descriptions of how to correctly put the current IPTC Core and IPTC Extension fields to use in Photoshop CS5)

User's Guide to the IPTC-PLUS Toolkit
(descriptions of how to correctly put the current IPTC Core, IPTC Extension & PLUS fields to use in the Javascript plug-in for Adobe Bridge for CS3 or later. Guide is included in full download)

User's Guide to the IPTC Core
(descriptions of how to correctly put the current IPTC Core fields to use in Photoshop CS3/CS4))

Caption and Keywording Guidelines
(Guidelines on how to write captions and keywords that will help you and others find your images)

Preserving Technical Photo Metadata
(a 10 page PDF written by INFRA staff on behalf of the IPTC Photo Metadata Working Group which
details digital photography workflows and pain points on where metadata may be inadvertently lost)

Guidelines for Handling Image Metadata, version 1.0.1
February 2009
Metadata Working Group (site offline after September 2018 - view MWG cache on Internet Archive)
The Metadata Working Group (MWG) — a consortium of Adobe, Apple, Canon, Microsoft, Sony, and Nokia — was formed in 2006 to publish technical specifications focused on the preservation and seamless interoperability of digital image metadata. Version 1.01 (issued February 2009) is available as a downloadable pdf at this site which establishes guidelines for handling metadata in images for all branches of the image-making and image-using industries.  A set of tools and test files are also available which can be used by developers who provide applications or services which handle photo metadata.

MetaSurvey of Stock Distributors
The first phase centered on a comprehensive survey of metadata practices among major stock image distributors. The study looked at a representative group which included Getty Images, Corbis, Jupiterimages, Masterfile and Alamy.  SAA conducted extensive random sampling of digital image files available on their websites to document the presence of metadata in both "thumbnails" and larger "preview" images. The team then tracked sample images to see what happens to embedded metadata as files are forwarded on from distributors to multiple sub-distributors.

Preliminary findings confirmed what SAA has long suspected: Too many images in the licensing market lack key identifying and content information.

After presenting our preliminary findings at major industry conferences including the 2008 Microsoft Pro Photo Summit and 2008 International Photo Metadata Conference, and sharing them with stock distributors and fellow association leadership, the SAA Photo Metadata Project team gained a better understanding of the challenges that need to be met to implement best practices across the licensing industry.

A white paper report of MetaSurvey findings is currently in development.

MetaSurvey of Photographers
With the launch of the Project web site, the second phase of our MetaSurvey begins with an online questionnaire directed to pro photographers of all types. We hope to gain broad participation in the survey which will give us a better idea of the level of metadata use in the pro photo comunity, including types of metadata embedded, software tools used, and insights into digital imaging workflows.

Photographers, Take the MetaSurvey!

Later in 2009, a report of our findings will be posted to this site.

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.

Why store metadata in image files?
Information stored in an image file is always with the image, no matter where it travels. In this sense, the information is the image. Think of today’s digital image files as packaged bundles of information, written (for the most part) in standard formats.

What types of metadata can we include in image files?
Digital image files can include descriptive, technical and administrative information about the image.

What metadata standards can we include in image files?
JPEG, TIFF, PSD, Raw and several other file formats can can contain IPTC-IIM, IPTC Core, IPTC Extension, PLUS, Exif and Dublin Core metadata.

What are the standards?
The formats and fields for storing metadata have evolved over the past couple decades, beginning with a standard - or “schema” - based on a multimedia Information Interchange Model created by the International Press and Telecommunications Council and adopted by Adobe in 1995 for its Photoshop products.

The original ("legacy") IPTC-IIM schema includes widely compatible fields identifying an image’s creator or rights holder, capture time, capture location, caption, headline, title, copyright notices and other basic information. IPTC Core and IPTC Extension build on the legacy of IPTC-IIM by adding more types of descriptive and administrative information, along with a more robust data format, XMP, and fields to accommodate the needs of the stock photography and cultural heritage communities.

Dublin Core is a schema for libraries in a wide variety of industries. It includes 15 basic components, five of which map to IPTC fields.

The PLUS system is a metadata standard that identifies and defines image-use licenses, along with a format and tools for generating a string of characters that can identify a copyright holder, user, scope and terms of a licensed image use.

Exif metadata include technical information about an image and its capture method, such as exposure settings, capture time, GPS location information and camera models.

How do we store metadata?
Image files include metadata, packaged separately from the pixel data that make up the visual image. Our bento box illustration might help you visualize this.

The initial method for storing metadata in image files originated with Adobe's TIFF format and was adopted by others. Since it stores the metadata – IPTC-IIM, and/or Exif – as "blocks" of data, it's referred to as Image Resource Block IRB format data. Sets of IRBs can be "nested," allowing multiple schemas in the same file. But this method of storing numbered "tags" faces tight size limits within the file header.
XMP is a newer, more flexible storage method – introduced by Adobe in 2001 and partly based on the XML language – for storing and accessing image metadata. It can store metadata within an image file or in an accompanying sidecar file, and it permits creation of custom metadata fields. In addition, XMP supports Unicode, allowing metadata to include language-specific characters (such as umlauts and accent marks) and even character-based alphabets such as Japanese, Chinese and Cyrillic. Unlike IRB, XMP fields have no character limits.

XMP can store IPTC Core, along with IPTC Extension, Dublin Core and PLUS metadata.
Exif, generated by capture devices, is both a storage format and a schema.

Do we need to worry about older storage methods?
Although the newer XMP format is replacing IRB for metadata storage, your metadata tools should support both, because:

• Older tools that don't support XMP (few did before 2005) will likely only read and write IRB data. Files created with older tools may only contain IRB-format data. However, many newer tools will read that information and translate it into XMP format.
• Some newer tools only store XMP-format metadata.
• A file edited by several different tools may have data in both formats, possibly with slightly different versions of the same data in each.

This can happen several ways, but one cause is the legacy IPTC-IIM schema limits the number of characters per field. An IPTC Core field might be truncated when saved in a corresponding IPTC-IIM field. When moving back and forth between tools that only understand the legacy format and those that recognize both the newer and older formats, synchronizing the information becomes extremely important.

Some software automatically recognizes both formats (the IRB format used to store IPTC-IIM and the XMP format that stores IPTC Core and other schemas) and synchronizes the information. But your workflow - the order in which you use different software - can make a big difference. In general, once you have used a newer tool that writes in both XMP and IRB, avoid using an older tool that only writes IRB format.

Why does the information I entered in "Author" show up as "Creator" in another program?
Several fields are "shared" between different schemas and field name labels. What one software program calls "Object Name," another may call "Document Title" or "Title." Part of this problem stems from changes in Field Names as schemas have evolved. In some cases, software programs are responding to users' requests to use legacy field names. In others, software developers have chosen to use a different name. Some software even gives users a choice of which Field Names to use.
The bottom line is the metadata can be "mapped" to corresponding fields regardless of what they're called. See the  IPTC Core Mapped Fields PDF on the linked page for more information on how fields are mapped between various imaging software.

How can I include metadata in image files?
Working with a wide variety of software, you can embed descriptive and identifying metadata in standard file formats, such as TIFF, JPEG and PSD. You can also embed such data in Raw image files, but there can be pitfalls. Proprietary Raw formats are neither standardized nor publicly documented. For now, it’s best to attach metadata in a sidecar, such as an Adobe .xmp, file, unless you convert your images to DNG format. See our Tutorials for more information on working with specific software programs.

Which metadata fields are most important?

While it's important to fill in as many photo metadata fields as possible with accurate and complete information, a few basic fields are considered critical. They include information related to Copyright and Contacting the creator and/or rights holder. Creators should enter this information as soon as possible in their workflow, in-camera if possible. Users who receive images without these critical fields should add them - if they're aware of the correct information - to any images they intend to retain for even a few days. And they should ensure such information is never stripped from image files.

Additionally, as soon as possible in their workflows, creators and users should ensure rich metadata are present in all image files, including such fields as:

• Caption/Description
• Keywords
• Unique identifiers (such as working file numbers)

To learn more about the importance of metadata to workflows and commerce, please see The Metadata Manifesto.

Do pictures from my smartphone pose a privacy risk?

While it's possible that your smartphone may embed information about your location (via GPS tags in the Exif metadata), this is something you can control. Some phones ask whether you want to share location data, or allow you to turn location services off. In addition, many of the services that may be used to share images have a tendency to strip (remove) all of the Exif data -- of which the GPS data are a part. The Snopes page about this issue gives some additional details that are worth a read if you are concerned.

An analogy may help:
Think of a digital image file as a box.
In that box - as in a Japanese bento box - are sections or compartments.

As trays in a bento box hold several types of food, virtual compartments in image files can hold several types of data – from the pixels that make up the image to the text that identifies and describes the image.

Not all image file formats have these compartments. But JPEG, TIFF, PSD, Raw and several other file formats can include any or all the following standard types of metadata:

IPTC-IIM
Often called "legacy" IPTC, this schema was developed in the early 1990s, primarily to aid news organizations in captioning early digital images. Its primary advantage is that most image editing and management programs can read and write its widely compatible fields.

IPTC Core & Extension
This newer schema builds on the legacy of IIM by adding more types of descriptive and administrative information, including new fields to accommodate the needs of the stock photography and cultural heritage communities, packaged in a more robust data format, "XMP."

PLUS
The Picture Licensing Universal System for identifying and defining image-use licenses, describes a schema and tools for generating a string of characters that can identify a copyright holder, user, scope and terms of a licensed image use.

XMP
This is the newer data format used by IPTC Core and Extension for storing and accessing image metadata. It enables metadata storage within an image file or in an accompanying sidecar file, and it permits creation of custom metadata fields.

Exif
These metadata, often created by cameras and other capture devices, include technical information about an image and its capture method, such as exposure settings, capture time, GPS location information and camera model.

Dublin Core
Many image libraries and a wide variety of industries store information with image files using this schema. Several of its fields are interoperable with IPTC formats.

Recommended Reading

Introductory Basics

Metadata Utilities

Standards, Specifications and Schemas

Guidelines and Best Practices in Metadata Applications for Images and Image Collections

Image Metadata Discussion Forums

Metadata Conference Presentations & Reports

Periodical Articles

Blogs

Reference and Lookup Tools

Recommended Reading

User Guide to the IPTC Core
Descriptions of how to correctly put the current IPTC fields to use to embed metadata in digital files.

A Short History of the IPTC (International Press Telecommunication Council) Standards
David Riecks, [n.d.]
An excellent beginners' outline that also answers most frequently asked questions.

Basic Metadata: A Photographer's Best Friend
by Ethan G. Salwen
ASMP Bulletin, fall 2007

Basic Metadata: Don't Process Without It
Adding Contact and Copyright Metadata to Your RAW Processing Workflow
by Ethan G. Salwen
AfterCapture magazine, Oct/Nov 2007
Addressing practicing photographers, Salwen advocates adding metadata to RAW images as a first step in processing, using templates for key metadata.

UPDIG: Universal Photographic Digital Imaging Guidelines, version 4.0
September 2008
The UPDIG guidelines aim to establish photographic standards and practices for photographers, designers, printers, and image distributors. They cover Digital Asset Management, Color Profiling, Metadata, and Photography Workflow.  Separate Guidelines for Photographers and Image Receivers are available on this site.

Introductory Basics

These sources provide an introduction to the problem of image data and metadata interchange, and early steps toward the solution.

A Short History of the IPTC (International Press Telecommunication Council) Standards
David Riecks, [n.d.]
An excellent beginners' outline that also answers most frequently asked questions.

SAA's Metadata Manifesto, issued July 2006
This site provides both a web version and a downloadable PDF outlining a proposal from the Stock Artists Alliance for the adoption of guiding principles, standards and technology to promote image metadata use among image-using industries around the world.

IPTC Photo Metadata White Paper 2007, Document Revision 11 [added by jldt 3/10]
Outlines metadata properties vital to image interchange, and workflows in current use by various types of image creators and users.

Basic Metadata: A Photographer's Best Friend
by Ethan G. Salwen
ASMP Bulletin, fall 2007

Metadata Utilities

Jeffrey Friedl's Online Metadata Viewer
A web based utility for reading Exif, XMP, IPTC, ICC, etc., data in most file types (including JPEG, TIFF, PSD, RAW, NEF, CR2, MP3, WMV, etc.) whether remote or local.  Includes a button that can be dragged and dropped into one's local browser button bar (Compatible with recent versions of the Firefox and Safari browsers).  The most flexible image metadata web-based viewer now available.

ExifTool
ExifTool is a platform-independent Perl library plus a command-line application for reading, writing and editing meta information in image, audio and video files. ExifTool supports many different types of metadata including EXIF, IPTC, XMP, and many others. ExifTool is also available as a stand-alone Windows executable and a Macintosh OS X package.

ExifTool GUI for Windows v3.10
[released April 4, 2008]
View Exif, IPTC, XMP, Maker Notes and more. This utility takes Phil Harvey's command line ExifTool utility and gives it a Graphical User Interface.

Photo Info (Exif only) for Mac
[Version 2.0.1 released Sept, 2006]
A simple Exif metadata viewer for the Macintosh operating system.

Microsoft Pro Photo Tools 2
Utility that permits viewing and editing image metadata from within Windows Explorer.  Emphasizes adding GPS data, though currently only writes metadata using the XMP format.

Exif Viewer 1.45
A Firefox addon, by Alan Raskin.  Displays the Exif and IPTC data in local and remote JPEG (only) images.

XMP metadata extractor (Jpeg only)
A web based utility for extracting the XMP from a JPEG file whether remote or local.

Standards, Specifications and Schemas

Photo Image File Format Specifications

JPEG
JPEG File Interchange Format, version 1.02
Issued September 1, 1992

TIFF
TIFF Revision 6.0
Final, June 1992
Adobe developers' file standards for TIFF file type.

PSD
File Standards for Photoshop PSD file type.
Updated May 2008
Parts copyrighted by Thomas Knoll

Photo Metadata Standards & Specification Schemas

Dublin Core
Dublin Core Metadata Element Set, Version 1.1
A ready reference to all Dublin Core elements;  includes references to controlled vocabularies available for individual elements.

DCMI Metadata Terms
Dublin Core Metadata Initiative
Recommendation of the DCMI Usage Board, issued January 2008.

IPTC Core
"IPTC Core" Schema for XMP, version 1.0
Specification Document, revision 8
IPTC 2005.
XMP value types and schema properties are given here, as well as a list of deprecated legacy IIM metadata elements mapped to current XMP values.

XMP
XMP (Extensible Metadata Platform)

XMP: Adding Intelligence to Media
XMP Specification
Adobe, 2005
Data and storage models, schemas, and embedding in image files.

IPTC IIM (Legacy)
IPTC Standard Photo Metadata 2008
IPTC Core, Specification Version 1.1
IPTC Extension, Specification 1.0
Document Revision 2
IPTC, 2008.  Supersedes Document Revision 1.
The only change mentioned is moving a table from one section to another.

IPTC-NAA Information Interchange Model (IIM), version 4, Rev 1, July 1999
Standard for representing and exchanging news information (both text and image).

Exif
JEITA  Exchangeable image file format for digital still cameras: Exif Version 2.2
JEITA CP-3451, established April 2002.
Published by Japan Electronics and Information Technology Industries Association (JEITA)
English translation of the standard, though the Japanese original is authoritative.

JEITA 49-1998
JEITA 49-1998 is the earlier version of the Exif standard.

Intellectual Property
PLUS Coalition License Data
PLUS (Picture Licensing Universal System)
Free registration required to access the standards information, which includes:

BETA version of the PLUS License Generator, a web based tool that generates a PLUS Universal License Summary file in XMP, suitable for embedding in digital image files. The License Generator is available in the "UsePLUS" menu of the PLUS website for free.
BETA version of a License Embedder and Reader (different versions for Mac and PC), that allows users to embed or read a Universal License Statement one file at a time. Future versions will support batch processing, saved license templates, saved user contact info.

For Digital Image Collections

XML

NISO Metadata for Images in XML Schema
Technical metadata for digital still images standard
The Library of Congress' Network Development and MARC Standards Office, in partnership with the NISO Technical Metadata for Digital Still Images Standards Committee and other interested experts, is developing an XML schema for a set of technical data elements required to manage digital image collections.

ANSI/NISO Z39.87 - Data Dictionary - Technical Metadata for Digital Still Images
Defines a set of metadata elements for raster digital images to enable users to develop, exchange, and interpret digital image files. The dictionary has been designed to facilitate interoperability between systems, services, and software as well as to support the long-term management of and continuing access to digital image collections.

VRA Core 4.0
Visual Resource Association, Data Standards Committee.
March 2007.
This is a data standard for the cultural heritage community, providing a categorical organization for the description of works of visual culture as well as the images that document them. It consists of a metadata element set as well as an initial blueprint for how those elements can be hierarchically structured.

World Wide Web Standards and Specifications

W3C Resource Description Framework (RDF)
RDF Vocabulary Description Language 1.0: RDF Schema
W3C Recommendation 10 February 2004
The Resource Description Framework (RDF) is a general-purpose language for representing information in the Web. This specification describes how to use RDF to describe RDF vocabularies. This specification defines a vocabulary for this purpose and defines other built-in RDF vocabulary initially specified in the RDF Model and Syntax Specification.

Encoding Dublin Core metadata in HTML
Informational Memorandum, not a standard.  Offers several examples of encoding.
IETF, December 1999.  © The Internet Society.

Image Annotation on the Semantic Web
W3C Incubator Group Report 14 August 2007
Offers use cases and solutions that illustrate vocabularies used in Dublin Core and VRA Core data elements.

Date and Time (W3C)
This document defines a profile of ISO 8601, the International Standard for the representation of dates and times. ISO 8601 describes a large number of date/time formats. To reduce the scope for error and the complexity of software, it is useful to restrict the supported formats to a small number. This profile defines a few date/time formats, likely to satisfy most requirements.

Guidelines and Best Practices in Metadata Applications for Images and Image Collections

User's Guide to the IPTC Core
(descriptions of how to correctly put the current IPTC fields to use)

Guidelines for Handling Image Metadata, version 1.0.1
February 2009
Metadata Working Group
A consortium of Microsoft, Canon, Sony, Nokia, and Adobe, launched July 2006, to establish metadata standards for images.  Version 1.01 of its Guidance, issued February 2009, is available as a downloadable pdf at this site.  It is intended to establish common standards among all branches of the image-making and image-using industries.

Learn how to add photo metadata, like descriptive and rights information, to your digital image files using popular professional software with some help from our tutorials. You can read them online, download as a PDF, or view many as a screencast / video tutorial.

Tutorials for Adobe Photoshop File Info, Adobe Bridge, Camera Bits Photo Mechanic and Microsoft Expression Media are available now.

If you are curious as to whether your chosen software application supports the IPTC Core, or the older "legacy" form (Information Interchange Model or IIM) of IPTC, check out the list maintained by the IPTC of Software supporting IPTC photo metadata standards IIM and "IPTC Core."

Coming soon.. Adobe Lightroom.