cater for new cameras. Assessment: Software could support raw formats without DNG, by using reverse engineering and/or dcraw; DNG makes it easier, and many software products can handle, via DNG, images from cameras that they have no specific knowledge of. An unresolved restriction is that any edit/development settings stored in the DNG file by a software product are unlikely to be recognized by a product from a different company. (This problem is not specific to DNG). In-camera use by camera manufacturers: to be suitable for many camera manufacturers to use as a native or optional raw image format in many cameras. Assessment: About 12 camera manufacturers have used DNG in-camera. About 38 camera models have used DNG. Raw image formats for more than 230 camera models can be converted to DNG. Multi-vendor interoperability: to be suitable for workflows where different hardware and software components share raw image files and/or transmit and receive them. Characteristics All of the above objectives are facilitated or enabled by most of these characteristics: Freely-available specification: this can be downloaded from the Adobe website without negotiation or needing justification. Format based on open specifications and/or standards: DNG is compatible with TIFF/EP, and various open formats and/or standards are used, including Exif metadata, XMP metadata, IPTC metadata, CIE XYZ coordinates and JPEG. Self-contained file format: a DNG file contains both the raw image data and metadata needed to render an image without needing additional knowledge of the characteristics of the camera. Version control scheme: it has a version scheme built into it that allows the DNG specification, DNG writers, and DNG readers to evolve at their own paces. Freely-available source-code-based software development kit (SDK): there is an SDK; it is source-code-based (as can be verified by examination); and it can be downloaded from the Adobe website without needing justification. Documented to have no known intellectual property encumbrances or license requirements: there is both a "Digital Negative (DNG) Specification Patent License" which says that anyone can exploit DNG, and a statement that there are no known intellectual property encumbrances or license requirements for DNG. Lossless and lossy compression (optional): DNG support optional lossless and (since version 1.4) also lossy compression. The lossy compression losses are practically imperceptible in real world images. 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