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Digital Photography common questions and answers

Question: What is EXIF data and how can it be used?

Answer: Almost all new digital cameras save JPEG (jpg) files with EXIF (Exchangeable Image File) data. Camera settings and scene information are recorded by the camera into the image file. Examples of stored information are shutter speed, date and time, focal length, exposure compensation, metering pattern and if a flash was used.

Many digicam owners find EXIF data useful to study when comparing successful images to those which are not. The information is a great learning tool for those who want to understanding how various camera settings effect the exposure of digital images.

EXIF data can be read by applications which support JPEG such as web browsers, image editing programs and some printer software drivers. Your digicam probably came with an image viewer which lets you view EXIF information for each image. If your printer supports EXIF, the driver uses the information to automatically enhance images which may result in a better looking print outs.

Since EXIF information is exclusive to the JPEG, the data will not be in an image if saved in another format such as TIFF. If you edit an image in certain image editing programs, EXIF data can also be lost. Remember, always edit copies of originals.

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Question: What is IPTC?

Answer: The International Press Telecommunications Council, based in Windsor, United Kingdom, is a consortium of the world's major news agencies and news industry vendors. It develops and maintains technical standards for improved news exchange that are used by virtually every major news organization in the world.

Currently about 55 companies and organisations from the news industry are members of the IPTC, they are drawn from all continents except South America.

The IPTC was established in 1965 by a group of news organisations including the Alliance Européenne des Agences de Presse, ANPA (now NAA), FIEJ (now WAN) and the North American News Agencies (a joint committee of Associated Press, Canadian Press and United Press International) to safeguard the telecommunications interests of the world's press.

Since the late 1970s IPTC's activities have primarily focussed on developing and publishing industry standards for the interchange of news data.

In particular, the IPTC defined a set of metadata attributes that can be applied to images. These were defined originally in 1979, and revised significantly in 1991 to be the "Information Interchange Model" (IIM), but the concept really advanced in 1994 when Adobe defined a specification for actually embedding the metadata into digital image files - known as "IPTC headers". IPTC Headers can be embedded into JPEG/EXIF or TIFF formatted image files.

In 2001, Adobe introduced something called "Extensible Metadata Platform" (XMP), which is an XML schema for the same types of metadata as IPTC, but is based on XML/RDF, and is therefore inherently extensible. The effort spawned a collaboration with the IPTC itself, eventually producing the "IPTC Core Schema for XMP", which merges the two approaches to embedded metadata. The XMP specification describes techniques for how to embed the metadata in JPEG, TIFF, JPEG2000, GIF, PNG, HTML, PostScript, PDF, SVG, Adobe Illustrator, and DNG files. Recent versions of all the main Adobe software products, (Photoshop, Illustrator, Acrobat, Framemaker, etc.) support XMP, as do an increasing number of third-party tools.

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