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Tuesday, February 26, 2013

DNG File Format & DNG Converter

In this excerpt from his book, digital master photographer and Photoshop Alpha-tester Jeff Schewe demystifies the DNG format for today and for the future

Digital Image Preservation

The long-term preservation and conservation of traditional analog photographic media has a tradition backed by research and known best practices. But digital photography (or any sort of digital object, such as video, audio, or text) is incredibly fragile and subject to corruption or erasure. It must be stored in redundant media and in redundant locations to be assured that it will still be available in the future. But even if you back up, archive, and store your digital images properly, will that guarantee that digital photography will be available in 5, 50, or 500 years? No.

The preservation of digital photography and digital content has become a major challenge for society. Since digital forms of media are rapidly becoming the principal and often only forms used to create, distribute, and store all manner of content, digital content now embodies much of the nation's intellectual, social, and cultural history. Digital content, particularly photography, is at serious risk of becoming unavailable to our future. If society loses its current intellectual, social, and cultural history, it's a major loss for future generations. Imagine if we no longer had access to the Civil War photographs by Mathew Brady; the portraits of people such as Winston Churchill, Babe Ruth, or Albert Einstein; or the photographic records of the Wright Brothers' first flight.

In December 2000, Congress appropriated $100 million for a national digital preservation strategy effort, to be led by the Library of Congress. The Library of Congress led the formation of a collaborative project called the National Digital Information Infrastructure and Preservation Program (NDIIPP; www.digitalpreservation.gov). The project furthers the library's mission "to make its resources available and useful to Congress and the American people and to sustain and preserve a universal collection of knowledge and creativity for future generations."

One of the most critical factors regarding the long-term preservation of digital content is the format in which the digital "objects" are stored. In order to have "sustainability," you need the ability to maintain a digital object in a technological environment in which users and archiving institutions operate. The sustainability factor is significant no matter what strategy may be adopted as the basis for future preservation actions: migration to new formats, emulation of current software on future computers, or a hybrid approach.

NDIIPP has identified seven sustainability factors that apply across digital formats for all categories of information (www.digitalpreservation.gov/formats/sustain/sustain.shtml):

• Disclosure: The degree to which complete specifications and tools for validating technical integrity exist and are accessible to those creating and sustaining digital content. Preservation of content in a given digital format over the long term isn't feasible without an understanding of how the information is represented (encoded) as bits and bytes in digital files.

• Adoption: The degree to which the format is already used by the primary creators, disseminators, or users of information resources. This includes use as a master format, for delivery to end users, and as a means of interchange between systems. If a format is widely adopted, it's less likely to become obsolete rapidly, and tools for migration and emulation are more likely to emerge from the industry without specific investment by archival institutions.

• Transparency: The degree to which the digital representation is open to direct analysis with basic tools. Digital formats in which the underlying information is represented simply and directly will be easier to migrate to new formats and more susceptible to digital archaeology. Transparency is enhanced if textual content, including metadata embedded in files, is encoded in standard character encodings and stored in natural reading order. Many digital formats used for disseminating content employ encryption or compression. Encryption is incompatible with transparency; compression inhibits transparency.


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