i recently posted on the x100 forum what i learned in the LL-LR tutorial, that the xmp files should always stay with the raw files and that they contain all the info LR needs to work with them in terms of adjustments, metadata and so on.
now somebody has pointed out that this is not necessary, that all this info is also stored in the lrcat file and the xmp´s are only needed for other programms such as PS.
1. can i now delete all the xmp´s, if i´m only working in LR?
2. do i have to keep them for PS or can they be recreated?
3. can other programs, like aperture, capture one or NX use those xmp´s ?
thanks for clarifying
The Lightrooom database (aka. LR catalog) contain all
information about your images that is needed in Lightroom. The xmp sidecar files are only written if you enable them to be written in the catalog settings. xmp files only exist for RAW files and only for the edits on the RAW file itself. Any virtual copies will not get xmp files written. The purpose of the xmp file is to be able to use Bridge in Photoshop or open dirently a file from Photoshop so that ACR can read the xmp file to know about the edits you have done in Lightroom. If you loose your LR catalog (should never happen) and you reimport a folder into Lightroom that contain xmp files, LR will import the settings from the xmp files into the LR database.
The settings in the XMP files can only be used by LR or ACR. They cannot be used by any other RAW converter. Although the xmp files are created in XML format the content for each XML tag is proprietary. Some of the tags are easily understood by others are not. See the attached part of an xmp file opened in a text editor.