Willem, On 10/06/13 07:09, Willem Ferguson wrote:
> Thank you very much for a long and thoughtful reply, and for the time it > took you to write such a complete response. > > I am really new to this topic of metadata management and therefore I > have had many misconceptions. I always thought that the XMP sidecars > just contained the EXIF metadata as a separate file since we do not wish > to modify the original RAW file and that, when exporting to JPG, the XMP > metadata is written into the JPG image as EXIF. Clearly I am wrong. The image itself can contain all kinds of metadata. The tags are split into groups and each group has a large number of tags. EXIF and XMP are just two of these groups of data. You may like to install exiftool and explore this using the -list and -listg options. For example, here are the groups that exiftool reports: Groups in family 0: AFCP AIFF APE APP0 APP12 APP13 APP14 APP15 APP4 APP5 APP6 APP8 ASF CanonVRD Composite DICOM DNG DV DjVu Ducky EXE EXIF ExifTool FLAC File Flash FlashPix Font FotoStation GIF GIMP GeoTiff H264 HTML ICC_Profile ID3 IPTC ITC JFIF JPEG Jpeg2000 LNK Leaf M2TS MIE MIFF MNG MPC MPEG MPF MXF MakerNotes Matroska Meta Ogg OpenEXR PDF PICT PNG PSP PanasonicRaw PhotoCD PhotoMechanic Photoshop PostScript PrintIM QuickTime RAF RIFF RSRC RTF Radiance Rawzor Real SVG SigmaRaw Stim Theora Vorbis XML XMP ZIP The groups also belong to a family. I've only ever seen family 0. > There are thus two separate sources of metadata: XMP and EXIF. For > instance the EXIF can contain information such as Location which the XMP > cannot. The XMP is restricted to the Simple Dublin Core (=DC) fields. I > have three questions (Internet links please, I do not expect you > yourself to spend a lot of time on this, let me do the legwork on the > Internet): XMP metadata should be written to an exported JPG file in the XMP group. There are a huge number of XMP tags available, but DT may restrict itself to use of a small subset of these. > 1) Does this mean that the DC XMP-based metadata is written as something > separate from the EXIF data block when creating a JPG copy of the master > RAW image? Does this mean that many software packages are aware of the > EXIF as well as the DC tagfields and can handle these? It's written as metadata in the XMP group. > 2) If this is correct, in general, how readable are the XMP (=DC tag > block) metadata by other software outside of dt? exiftool (and hence libexiv2) should be able to read any tag in any group. It depends on what the software decides to support. > 3) Then it should be relatively simple to use, within dt, more of the > Simple Dublin Core tags, since this comprises 15 tags in total, allowing > more dc fields for descriptors and tags. Use of more or all the simple > DC tags would already make a large difference in the usability of > metadata. Does this make sense at all? It all depends on what the DT developers decide to expose in the user interface and how it presents them. Regards, Tony. -- Tony Arnold, Tel: +44 (0) 161 275 6093 Head of IT Security, Fax: +44 (0) 705 344 3082 University of Manchester, Mob: +44 (0) 773 330 0039 Manchester M13 9PL. Email: [email protected] ------------------------------------------------------------------------------ How ServiceNow helps IT people transform IT departments: 1. A cloud service to automate IT design, transition and operations 2. Dashboards that offer high-level views of enterprise services 3. A single system of record for all IT processes http://p.sf.net/sfu/servicenow-d2d-j _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
