I've recently purchased Lightroom 4 and on the whole I'm very happy with it, but I have run into a problem. I have a few scripts which grab information from the XML-based XMP metadata block that's embedded in the DNG and JPG files that I use. I've found that images processed with Lightroom 4 no longer export the exif: and tiff: data.
To illustrate, a photo I exported with a previous version of Lightroom has the following data in the XMP block
tiff:Model="Canon EOS 40D"
There is, of course, a lot more information in the XMP block, but in a file exported using Lightroom 4 there is nothing in the XMP block with the exif: or tiff: namespaces so none of this information is available to any script which queries the XMP metadata. I'm pretty sure that the metadata is still there, embedded in the original EXIF data, as I can view it using the metadata panel in the Library module, but that's not accessible to my scripts as it's not in the XMP block. I've made doubly sure that the metadata has been saved and also double-checked all my settings and even tried to export the files multiple times with every different setting that I can think of (even though my current settings worked fine in previous versions) but the files never get the exif: or tiff: data.
I have called Adobe, but the best help they could give me so far was to post here and hope someone can help!
I just compared two JPEGs exported with LR 3.6 and LR 4.1RC. The tags you mentioned are exported neither by 4.1 nor by 3.6. These tags are only present in the normal Exif metadata, but not in XMP. Which version of LR 3.x did you use before? Perhaps Adobe changed something already in the later versions of LR 3.x. If this is the case, you have to use a script or tool that is able to read the Exif metadata directly.
In the XMP metadata in the file exported by LR 3.6, I see only crs (camera raw), aux (e.g. serial no.) and some other XMP namespaces, but no exif or tiff.
P.S. I viewed the metadata of the exported files with exiftool. File format was JPEG (with "quality" setting, not with "limit file size", because apparently there are still some XMP differences between these two modes).
I suspect this may be due to Adobe adhering to the latest recommendations of the Metadata Working Group. If I recall correctly, certain information that natively exists in the image file is no longer replicated in the XMP block. You may need to adjust your scripts accordingly, as the MWG approach is likely to be the standard for the foreseeable future. I believe the change occured around the LR 3.5 timeframe.
To follow up some more...
The latest MWG spec may be found here. A discussion of the issue is on page 22; specifically:
"However, this document changes this earlier XMP guidance and recommends that Exif and Tiff device properties only be mapped to XMP in the case the file format does not support Exif natively."
The MWG spec dates to Nov 2010, and as I noted earlier, Adobe adopted this guidance sometime last year for LR and, I believe, Photoshop as well.
That sounds like the answer then. I have been using Lightroom 3.2 until I upgraded to 4 so that would also fit with your observations. I must say that's a really frustrating change as it makes the information a lot harder to retrieve. I'd certainly appreciate it if Adobe gave us the option to include the data for backwards compatibility, but I guess that's unlikely.
Thanks a lot for your help,
I hear you. I too got caught by the MWG standard, and had to go through many thousands of my scanned images and remap the digitized dates that I had set. In the big picture, however, the goals of the MWG are very good, and I applaud the effort to create a more unified standard.