Digital negatives

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Digital Negative (DNG)
DNG tm.svg
File extension : .dng
Developed by: Adobe Inc.
Initial release: September 27, 2004
Current version: 1.5.0.0 (as of May 2019)
Type: Raw data format
Container for: Metadata can be embedded in XMP , Exif or IPTC formats.
Extended by: TIFF 6.0
Website : Digital Negative (DNG) on adobe.com

The digital negative format ( DNG , German digital negative ) is a patented , open , lossless raw data format that was developed for digital photography .

It was published in September 2004 and, according to the manufacturer Adobe Inc., was developed with the aim of replacing the various proprietary formats used by digital camera manufacturers and establishing themselves as the standard. The release was accompanied by the first version of the DNG specification and various products including a free DNG converter utility. Since DNG was released, all Adobe photo manipulation products (such as Adobe Photoshop and Adobe Lightroom ) support the DNG format.

use

Adobe has disclosed the specifications of the format and provides further information on implementation. In addition to the in-house image processing programs Adobe Photoshop (from version CS ), Adobe Photoshop Elements (from version 3.0) and Adobe Photoshop Lightroom , programs from other providers also support the format, for example:

There are also converters for converting manufacturer-specific raw data into DNG files, in addition to the Adobe DNG converter from the manufacturer, for example the DigiKam program .

With the Leica-Digital-Modul-R delivered in 2005 , the format was used for the first time directly for the storage of image data. The Hasselblad H2D -39 was the first digital SLR camera that can save either in its own or in DNG raw data format; other manufacturers followed:

Technical implementation

The format is based on an extension of the Tagged Image File Format . In addition to the image data, any metadata can be embedded. This enables - even extensive - extensions that can be integrated at any time without loss of compatibility and thereby manage without separate so-called sidecar files (or comparable redundant data storage) and enables high portability of the files between different computer platforms. DNG enables transparencies and 32 bit color depth .

Advantages and disadvantages

In addition to the advantages already known from the underlying raw data format, the following should be mentioned:

  • In contrast to most existing raw data formats, the file structure, which is openly documented, facilitates the development of software by third parties, both for writing and reading.
  • Loss-free compression is possible, but not mandatory and - unlike the underlying TIFF - takes place according to specified conditions, which should further improve portability.
  • DNG does not require raw data to be available in mosaic form (according to a Bayer color scheme). It therefore also supports Sigma cameras with Foveon sensors, for example .
  • Metadata can be accommodated directly in the image file - without the dependency on additional files ( e.g. xmp ) or image databases in which information about processing, recording, development or catalog information would otherwise have to be stored, since the manufacturer's own formats are often only restricted or even limited after recording no longer provide write access to the file.

In practice, at least so far, there are also disadvantages:

  • So far, apart from the above-mentioned exceptions, cameras with native DNG support have been rare, so that the individual image processing process has to be supplemented by the intermediate step of conversion.
  • Even cameras with DNG support often do not fully implement the format (for example, no lossless compression, limited or incomplete creation of metadata).

DNG as an archive format

So far, DNG has not established itself as a format for long-term archiving. The "Practice Rules 'Digitization'" published by the German Research Foundation describe the DNG format as well as the proprietary RAW formats of various manufacturers as "unsuitable as an archive format". It is seen as problematic that the format is open, but protected by a patent, which could hinder the implementation of file viewers in the future.

In contrast, the Library of Congress lists the DNG format on their "Recommended Formats Statement" page. As early as 2010, institutions in the USA were described that relied on DNG as their "master format".

Version history

The specification has been revised several times. Previous versions and their innovations :

  • 1.0 (September 2004): Initial version
  • 1.1 (February 2005): Preservation of masked pixels
  • 1.2 (April 2008): Camera profiles, see also "DNG Profile Editor"
  • 1.3 (June 2009): Opcodes (e.g. lens corrections)
  • 1.4 (October 2012): "Default User Crop", transparency , floating point numbers ( HDR ), lossy compression , proxies
  • 1.5 (May 2019): Depth Maps, Enhanced Image Data

Web links

References and comments

  1. ↑ Digital Negative (DNG) Specification Version 1.4.0.0. (PDF) In: adobe.com. Adobe Inc. , June 2012, p. 12 , accessed on July 31, 2017 (English): "DNG is an extension of the TIFF 6.0 format, and is compatible with the TIFF-EP standard. It is possible (but not required) for a DNG file to simultaneously comply with both the Digital Negative specification and the TIFF-EP standard. "
  2. ↑ Products that support DNG in some way ( English ) Barrypearson.co.uk. Retrieved May 20, 2010.
  3. ↑ Phantom 2 Vision will capture Adobe DNG RAW and provide Ground Station capabilities ( English ) DJI. December 4, 2013. Retrieved September 19, 2016.
  4. ↑ Heise : Adobe expands DNG specification
  5. ↑ DFG rules of practice "Digitization". (PDF) In: dfg.de. Deutsche Forschungsgemeinschaft , December 2016, p. 21 , accessed on December 11, 2019 : “Even the various proprietary RAW formats are not suitable for saving the image recording as a master, especially since they can often only be displayed with the associated RAW software . The cross-platform, camera-independent Adobe RAW format DNG has also not caught on and is therefore unsuitable as an archive format. "
  6. ↑ Recommended Formats Statement - II. Still Image Works - ii. Photographs - Digital. In: loc.gov. Library of Congress, accessed December 11, 2019 .
  7. ↑ Michael J. Bennett and Barry F. Wheeler: Raw as Archival Still Image Format: A Consideration. (pdf) In: Published Works 23. Univ. of Connecticut Library, 2010, p. 8 , accessed on December 11, 2019 (English): "DNG is currently adopted as an archival master format at The National Gallery of Art, Washington, DC and at The Art Institute of Chicago [70] . The National Gallery in particular acknowledges the specification's high end image data storage, growing adoption, and single file workflow practicality (archival masters> production derivatives) [71]. "
  8. ↑ Tom Hogarty: DNG 1.4 Specification Notes. In: Lightroom Journal (blogs.adobe.com). Adobe Inc., October 5, 2012, accessed August 1, 2017 .
  9. ↑ On the subject of "DNG Profile Editor" see z. B. Mike Schelhorn: The DNG Profile Editor. In: Macwelt online. November 19, 2009, accessed August 1, 2017 .