On 06/10/2013 08:09 AM, Willem Ferguson wrote: Hi!
> 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. Not completely. They may end up at a point your tools don't expect them though. XMP is (relatively) new. > There are thus two separate sources of metadata: XMP and > EXIF. And IPTC at least... > 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. Not quite. Actually, XMP is just an XML structure that could contain any metadata. It could also implement a larger scheme. Just at the moment darktables input is restricted to the dublin core simple. > 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? Jepp. As XMP block. Basically, you embedd an XML stub into the image. XMP here is just like the xmp sidecar file. If you search for pointers, most likely you'll stumble upon Adobes specs. (BTW: XMP also exists for PDF etc.) > Does this mean that many software packages are aware of > the EXIF as well as the DC tagfields and can handle these? AFAIK the XMP block beyond exif is not (yet) known to many software packages. To my limited experiences many tools seem to prefer the (older) IPTC tags and ignore xmp. If they read something beyond exif at all. > 2) If this is correct, in general, how readable are the > XMP (=DC tag block) metadata by other software outside of > dt? exiftool will handle all you need there. The xmp itself is just XML so you can basically read it with everything that can process XML. The exposed Dublin Core on the other hand is a very wide spread standard for (simple) data interchange. All this is not bad, the main problem is that the Dublin Core is just what the name suggests: a /core/ data set. It's pretty simple and thus limited. (cf. www.dublincore.org) > 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. In principle, yes. A further step would be to use Dublin Core Qualified. However, I feel in the area of photography one should definitely consider IPTC as well, especially as it contains many photography related and specific metadata fields. (cf. http://www.iptc.org/cms/site/index.html?channel=CH0099) I feel many of them are more suiteable than the general Dublin Core fields. They can be expressed and exposed in the same xmp structure as the Dublin Core. But JPG/Tiff contain special structures for them. > 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 does. And I can't resist to (freely) cite at least two lines from a talk this morning: "Metadata are at least as important if not more than the data itself. Without them you can't find nor understand your data." And "Archival is more than putting files on a reliable storage." Open Access to Publications and Data in the Research Field ‚Structure of Matter‘ of the Helmholtz Association. (Slides are not up on the web yet.) -- Kind regards, / War is Peace. | Freedom is Slavery. Alexander Wagner | Ignorance is Strength. | | Theory : G. Orwell, "1984" / In practice: USA, since 2001 ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Darktable-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/darktable-users
