Digital Negative

Digital Negative (DNG) is a patented, open, non-free lossless raw image format written by Adobe used for digital photography. It was launched on September 27, 2004. The launch was accompanied by the first version of the DNG specification, plus various products, including a free-of-charge DNG converter utility. All Adobe photo manipulation software (such as Adobe Photoshop and Adobe Lightroom) released since the launch supports DNG.

DNG is based on the TIFF/EP standard format, and mandates significant use of metadata. Use of the file format is royalty-free; Adobe has published a license allowing anyone to exploit DNG, and has also stated that there are no known intellectual property encumbrances or license requirements for DNG. Adobe stated that if there were a consensus that DNG should be controlled by a standards body, they were open to the idea. Adobe has submitted DNG to ISO for incorporation into their revision of TIFF/EP.

Rationale for DNG

Given the existence of other raw image formats, Adobe's creation of DNG as a competing format implies that DNG is unusual and satisfies objectives that other raw image formats do not. These objectives and the associated characteristics of DNG, as well as assessments of whether these objectives are met, are described below. Increasingly, professional archivists and conservationists, working for respectable organizations, variously suggest or recommend DNG for archival purposes.

Digital negative (transparency)

The digital negative is a new technology which allows photographers to use digital files to create negatives on transparency film. These negatives can be used to contact print, or in some cases if the negative is made large enough (about 4x5") they can be enlarged. It is different from the Digital negative (DNG) file format, although this format may be used to create the digital images.

Creation of digital negatives

Before creating a digital negative it is important to know the process to which it will be applied. Since contemporary inks and printers cannot cover a gamut as wide as traditional silver negatives and it is imperative that each process have its own tonal curve to apply to a photograph so that the photographer can take full advantage of its gamut. Also, different processes react to colors in different ways; sometimes photographers print out a monochromatic negative in a specific color to get a specific contrast range. For example, some use purple inks and low contrast curves for the small gamut of cyanotype printing, while the platinum/palladium process necessitates a high contrast curve that works best with green ink. Before the color cast is added, however, it is important to remember to invert the image to ensure that the negative prints a positive if contact printing (some also flip their image horizontally since the final print will be a mirror image of the negative), or sometimes it may be left as a positive (in the case of a positive image on a dry or wet plate).