Alexander, 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. 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): 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? 2) If this is correct, in general, how readable are the XMP (=DC tag block) metadata by other software outside of dt? 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? Kind regards, willem On 09/06/2013 21:31, Alexander Wagner wrote: > > On 06/08/2013 07:42 AM, Willem Ferguson wrote: > > Hi! > > [...] >> metadata into the JPG images. However, I have several issues. >> >> 1) The metadata on the right hand of the light table are >> not all shown in the image information block on the left >> hand of the light table. For instance the Title tag on the >> right is not shown on the left. Is there any way to show >> all the metadata fields in the image information block? >> My installation (V1.2.1) only shows Title, Creator and >> Copyright in the image information. Is there, within dt, a >> way to configure which tags are shown on the left? > > I think your problem here is that "left" refers to > Exif-metadata, and what you want to see there are actually > xmp-metadata. That's to my knowledge why they display on the > right hand side. > >> 2) When using standard Linux utilities, many metadata >> fields are not shown or have different names. > > Sure. dt only writes the dublin core block of xmp. > >> In Nautilus file properties, the only metadata shown are >> Description, Keywords, Creator and Copyright. > > Again, the dublin core block of the xmp. Note it's even > dublin core simple. That doesn't give you much fields and > the granularity is "limited" to be polite to the dublin core > ;) > >> Note that the 'Rights' field in dt becomes 'Copyright'. > > That's ok, IMHO as it is just dc:rights and this tag gets a > "proper" name for display. But it's just a name. Internally > its just alway the same. > >> A trivial detail, but >> I thought the Exif fields had standardised names?? > > It's xmp what you see, not exif. It seems you mix those two. > >> In Image Viewer, the dt 'Creator' field becomes 'Author' > > Again interpretation of dc:creator from the dublin core (dc) > entity. Usually (though not quite correct) dc:creator is > interpreted as "author" as the dc field designations are > more or less invented for more bibliographic entities. > And usually if some bibliographic entity calls a creator it > is the author. Now, quite some tools do tihs as well and > don't think about why the h... the dublin core people called > it creator and not author ;) The used dc set (dc simple) > does not have "subdesignation" so you have no real roles. > > IMHO the main issue is, that dc (especially dc simple) is > nice, but to small for anyhting decent. Its useful to display > a real metadata scheme in a standardized, simplified way > only. But to rely on it for metadata storage is difficult. > Just way to few data. (Imagine entities like dc:identifier, > that have to hold anything like isbn, issn, doi and all > other identifer-like things e.g. even a local db counter.) > >> and there is a Location field that clearly is different >> from Longitude and Latitude in dt. > > Nope. dt does not support IPTC (unfortuantely) so you don't > have the IPTC-entities location, sublocation, country, > country code etc. And they are not part of the dublin core > simple so no entries in the dc: data eiter. This is really > difficult. The cleanest way to add them would probably be a > keyword chain like IPCT|locacion|country|Somewhere, but I > have to admit, trying this for entry in dt is a bit, hm, > well, PITA. :( > > gps coordinates on the other hand live in exif. > >> 3) If I wish to share images with a person (often using a different OS) >> there is not an easy and reliable way to predict which matadata that >> person will see. > > I think this is not true. Actually, the xmp block used by dt > is quite standardized. Main issue is that many programs > don't interpret xmp. They just expect it as this is a bit > new. They only expect IPTC which exists for a while as the > standard. And these blocks are just not there. So, they look > for something that does not exist and don't know about what > exists and you get nothing. > >> Is there any way to make sense of this? > > metadata are definitely one of the weakest spot of dt. This > is unfortunate, as the rest of dt is really great. > > As you're creating an jpg anyway you can resort to add the > metadata with another tool. I find mapivi very convenient > for this and it allows IPTC, XMP and exif, so you have > control of all fields relevant in the way it should be. What > I mainly do (might work for you as well): > > - Ingest from the camera to a direcory darkroom/ > - Work on the raws there in darktable > - Ignore all metadata fields of darktable > - Export the results to JPG in the same darkroom/ dir. > Filname of jpg == filename of raw > - Ingest darkroom/ to my mapivi structure and add metadata > there > > Mapivi will collate raw, jpg and xmp and handle them as one. > Metadata will be written to the jpg only, however. But as > mapivi is in perl and has a very simple plugin interface a > call against exiftool libs would allow to add metadata from > IPTC to your xmp files from dt. They stay usable for dt as > dt will just ignore those unknown namespaces (mainly > photoshop and iptc.) > > Probably this helps a bit. > ------------------------------------------------------------------------------ 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
