Questions about XMP creation

[Archive]

[Originally posted by salviati on 2009-09-15 00:42:23-07]

Phil - Thanks so much for your earlier help in writing filename data to the Keywords field.  After playing around with it today however, I think I may have to reconsider my methodology.  My SD cards include mostly RAW+JPEG, but with some stand-alone JPEG files as well.  I realized that adding the metadata to the files themselves was taking far too long, and interrupted other aspects of my workflow (which is a different matter).  Now I'm thinking about simply writing XMP files for each photo prior to importing into Lightroom.  I do have some fundamental questions about XMP that I haven't been able to figure out by searching this forum or any others, and I hope with your vast knowledge of the subject, you might be able to help.

1) Will .xmp files created from RAW files be compatible with JPEGs of the same name?  For example, if I have two files IMG_001.CR2 and IMG_001.JPG and create a file called IMG_001.XMP from the RAW file, will it still work with the JPG or is it incompatible?

2) Do XMP files have to contain the full EXIF and IPTC data of a file, or can it simply supplement the data already existing on the image.  For example, if I wanted to add just 1 keyword to an image by creating an XMP, can the XMP file just contain the added keyword or must it contain all the image's information?

3) This question is really about Lightroom, so feel free to ignore it if you wish: When Lightroom imports a JPG file, does it even recognize an XMP sidecar file?

4) Is it possible to create an exiftool script that creates an XMP file for all RAW files, and checks each JPG file to see if an XMP file already exists, and create one if it doesn't?

[Archive]

[Originally posted by exiftool on 2009-09-15 11:11:37-07]

Speed can certainly be an issue if you are editing the files on
the SD card.  It should be 10x faster or more if you do this from
the hard disk.

1) Things like image size may change between the CR2 and JPG
files, so this metadata won't be accurate if you use a common
XMP file.  However, this shouldn't affect lightroom because
the properties of the image itself must take precedence.

2) The XMP file can just supplement information in the image.

3) I would guess that lightroom looks for a XMP sidecar for any
image type.

4) Yes, with the -o option.  See the examples in the exiftool
sidecar
files documentation.

- Phil