A Metadata Manifesto
"A proposal by the Stock Artists Alliance for the adoption of guiding principles, standards and technology to promote image metadata use".
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A Metadata Manifesto
XMP (eXtensible Metadata Platform)
DNG has benefits in its own right as a common raw format. For interchange purposes, it is unique among raw file formats. It holds camera details within the file, so raw-handling products that have no built-in details for a camera model can still render a DNG because they can read the details from the DMG.
But DNG can also hold a considerable amount of metadata in XMP form. It is probably this combination that will have the greatest impact. Note the word "extensible" - while XMP supports familiar IPTC-like keywords or ACR settings, it isn't limited to them. (For example, it can support EXIF-like data too).
This is not the place for a sales-pitch for XMP. Some suitable links are provided elsewhere on this site. But here is some information I have been storing in my DNG files as XMP metadata for years, because in future this will give clues about their potential value. In other words, this is an important part of "archiving" - making these photographs "future proof". And this metadata can be copied into downstream Photoshop files and JPEGs.
- My name, copyright information, website address.
- Keywords describing the photo-shoot. Keywords describing the contents of individual photographs.
- Editing and settings information of ACR (Adobe Camera Raw): rotation, alignment, cropping, white balance, exposure, shadows, brightness, contrast, saturation, (sharpness - typically none), luminance smoothing, colour noise reduction, chromatic abberation correction, (vignetting correction - typically none), Curve, and several camera calibration settings.
Adobe have proposed that XMP should become an ISO standard. The core would be under the control of TC130, while specific parts would be under the control of other parts of ISO.
Books that provide both a vision and a current practical realisation of the use of XMP within DNG files include:
Products supporting XMP with DNG
These products support XMP within DNG files. I have personal experience of few of these products. John Beardsworth provided much of the information on this page in a number of communications, but any errors are mine.
|Photoshop CS + ACR 2.4||In||This reads DNGs with XMP metadata within them.|
|Bridge + ACR 3.x or Photoshop CS2 + ACR 3.x||In Out||DNG is the native raw format for ACR, holding settings in XMP form as well as the raw data. Other XMP metadata can be added too, and all can be displayed by Bridge.|
|Bridge + ACR 4.x or Photoshop CS3 + ACR 4.x||In Out||DNG is the native raw format for ACR, holding settings in XMP form as well as the raw data. Other XMP metadata can be added too, and all can be displayed by Bridge.|
|Photoshop Elements + ACR 3.x or ACR 4.x||In Out||DNG is the native raw format for ACR, holding settings in XMP form as well as the raw data. (Details tbs).|
|DNG Converter||In Out||This is one of the main ways of creating DNG files, and puts XMP metadata into them when it does so. It can merge the metadata in XMP sidecar files into a resultant DNG file.|
|DNG SDK||In Out||"The DNG SDK [Software Development Kit] provides support for reading and writing DNG files as well as support for converting DNG data into a format easily displayed or processed by imaging applications. This SDK can serve as a starting point for adding DNG support to existing applications that use and manipulate images or as an aid to adding DNG support within cameras". (It includes a binary distribution of the Adobe XMP SDK).|
|Lightroom||In Out||"Adobe® Lightroom™ is the efficient new way for professional photographers to import, select, develop, and showcase large volumes of digital images".|
|ACDSee Pro Photo Manager||In Out||Launched January 2006: "Powerful searching and organizing tools help you manage hundreds upon thousands of photographs effortlessly.... Integrate your workflow seamlessly with clients and colleagues by leveraging DNG (Digital Negative Specification) RAW format support".|
|BreezeBrowser Pro||In Out||This is included here as an XMP-editor, not as a raw converter. "Also displays Adobe DNG format raw files.... (v1.5): Editing of XMP IPTC data in ... DNG ... file formats".|
|This is an image browser. Photo Mechanic Version 4.4: "Photo Mechanic can embed IPTC and/or XMP data in TIFF-based RAW formats, including ... and Adobe DNG".|
|Doug Alcorn - Image Ingest Script for DNG||Out||"Now that Adobe's DNG Converter can be used from the command line, I've written a new script to ingest photos from compact flash, convert to DNG, and rename based on EXIF.... adding XMP metadata from a Template file".|
|Exiftool (Or Exiftool)||
|"ExifTool provides an extensible set of perl modules to read and write meta information in image files. It reads ... DNG (Digital Negative) images.... It writes ... DNG files.... Reads ... XMP ... Writes ... XMP ...".|
|Extensis Portfolio||In||Extensis Portfolio version 7 users can map catalogue fields to extensible XMP tags and import the data, though not GPS. Portfolio 8 can also read GPS metadata. It has no ability to write metadata to DNG files.|
|FastPictureViewer||In Out||"FastPictureViewer is a small and fast color-managed image viewer designed for professional photographers .... supports ... Quick Adobe XMP rating function ... Professional Edition available with TIFF, DNG ..."|
|idImager||In Out||"idImager V3 will allow you to read and write all XMP that currently exists in your DNG files.... This also includes raw converter information that ACR writes as XMP in a DNG. With idImager you can add additional metadata to the file and write that back to the DNG.... By default idImager V3 is configured with editor panels that show all metadata that is defined in the IPTC4XMP schema, but you are free to customize that to your own preference. idImager can be configured to ingest into DNG format, and also to add a user's "standard" XMP metadata to a set of DNG files".|
|In||"Imagero Reader is in Java written library for reading of image files.... DNG: Full resolution image can't be yet read, but thumbnail, preview and metadata can be read. Also: "EXIF, IPTC and XMP metadata editing".|
Microsoft Expression Media
|In Out||"iView 3.02 reads DNG files' XMP data from from Adobe, IPTC-Core, iView and other namespaces whose tags have been hard coded into the application. It writes metadata into DNG files in XMP format, including Adobe, IPTC-Core and iView-specific metadata such as its Catalog Sets, but cannot write other extensible custom metadata."
Microsoft completed the acquisition of iView Group Limited on June 22, 2006. MediaPro will become a new program, Microsoft Expression Media in spring 2007 . (iView. The DAM Book).
|PhotoME||In||"PhotoME is a powerful tool to show and edit meta data of image files.... PhotoME showns ... and the following camera RAW file types: ... Digital Negative (DNG). It can display the XMP in a DNG.|
|Photools - IMatch||In||"IMatch makes it easy to view, edit and organize your digital image collection.... Digital Camera RAW Formats ... Adobe DNG ... IMatch fully supports loading and displaying XMP information from .XMP sidecar files and embedded XMP data in ... DNG ...."|
|PicaJet - PicaJet FX||In Out||"Instantly organize thousands of photos automatically". PicaJet features: "Camera RAW files support including Adobe DNG.... Write the image annotations into the DNG files (XMP section)".|
|PicaJet - RoboImport||In Out||"RoboImport downloads your digital images straight from a digital memory card or a digital camera, renames them, and automatically perform's a number of image editing operations during transferring to your PC.... RoboImport batch processes your DNG conversions using Adobe's free DNG Converter.... New in 1.1 build 48: Added mapping IPTC to DNG XMP data".|
Extracting XMP from DNG files
There may be a need to extract the XMP metadata from a DNG file, and convert it into a text file, for example making it into an XMP sidecar file. I don't know of any tools specifically designed to do this, but there are methods of doing so:
- Microsoft Word can open a DNG file as though it is an ASCII text file. (Not as an image file). Having done so, the XMP metadata is close to the front of the file, and is fairly obvious. It will start with a string like:
<?xpacket begin="ï»¿" id="W5M0MpCehiHzreSzNTczkc9d"?>and end with a corresponding string like:
<?xpacket end="w"?>. The whole set of XMP can be copied into a text file, and will serve as an XMP sidecar.
- Adobe products can be "persuaded" to write XMP sidecar files even for DNG files. The DNG file must be made read-only. Then if an Adobe product needs to save XMP metadata, it will create and write an XMP sidecar file instead. (It is necessary, where relevant, to have the preference set to use XMP sidecars instead of the central database). So: make a whole set of DNG files in a folder "read only". Select them all in Bridge and open them all in ACR. Make a reversible change, then reverse it. For example, change sharpening from 0 to 100 then back. Or change WB from "as shot" to "tungsten" then back. ("Rotate" doesn't appear to be sufficient). Then click "Done". ACR should then generate a full set of XMP sidecar files in the same folder.