Technical Summary
A DNG file always contains data for one main image, plus metadata, and optionally contains at least one JPEG preview. It normally has the extension "dng" or "DNG".
DNG conforms to TIFF/EP and is structured according to TIFF. DNG supports various formats of metadata, (including Exif metadata, XMP metadata, IPTC metadata), and specifies a set of mandated metadata.
DNG is both a raw image format and a format that supports "non-raw", or partly processed, images. The latter (non-raw) format is known as "Linear DNG". Linear DNG is still scene-referred and can still benefit from many of the operations typically performed by a raw converter, such as white balance, the application of a camera color profile, HDR compositing, etc. All images that can be supported as raw images can also be supported as Linear DNG. Images from the Foveon X3 sensor or similar, hence especially Sigma cameras, can only be supported as Linear DNG.
DNG can contain raw image data from sensors with various configurations of color filter array (CFA). These include: conventional Bayer filters, using 3 colors and rectangular pixels; 4 color CFAs, for example the RGBE filter used in the Sony DSC-F828; rectangular (non-square) pixels, for example as used in the Nikon D1X; and offset sensors (for example with octagonal pixels) such as Super CCD sensors of various types, as used in various Fujifilm cameras. (Or combinations of these if necessary). DNG specifies metadata describing these individual parameters; this is one significant extension to TIFF/EP.
When used in a CinemaDNG movie clip, each frame is encoded using the above DNG image format. The clip's image stream can then be stored in one of two formats: either as video essence using frame-based wrapping in an MXF file, or as a sequence of DNG files in a specified file directory.
Read more about this topic: Digital Negative
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