Aperture currently has several issues related to metadata import/export under investigation. This article describes the issues and distinguishes them from one intentional aspect of metadata export which may be perceived as an issue.
Note: Aperture 1.1 with Mac OS X 10.4.6 or later resolves this issue (about updating).
If you export a version as TIFF or PNG, you may see that most of the EXIF data is missing. However, it's present when exporting to JPEG or PSD (assuming that you have updated to Aperture 1.0.1 and Mac OS X 10.4.4, or later). Keywords and IPTC data should export as expected. Note that PNG simply does not support EXIF.
Note: Aperture 1.1 with Mac OS X 10.4.6 or later resolves this issue (about updating).
Since the Open With External Editor command is creating a PSD or TIFF version, it behaves as described above. This means that if you have updated to Aperture 1.0.1 and Mac OS X 10.4.4, or later, that you would have metadata for a PSD but not a TIFF.
If you use a third-party application such as Photo Mechanic to apply metadata to RAW images prior to Aperture import, the metadata is not currently recognized in the Aperture metadata inspector. However, it remains part of the file and is present if you export the master.
Additionally, if you add metadata using Aperture, export the images, and then reimport them, the Import window won't show what you added in the fields following Add Metadata From. These fields are designed for adding new metadata at time of import, not for displaying old metadata.
Under certain circumstances with certain cameras, Aperture may not be able to import files which have had metadata added by Photo Mechanic or similar applications. Sometimes the file may import but then result in an "unsupported format" message.
Unlike applications such as Photo Mechanic, Aperture does not write IPTC and keywords to the original RAW file. Instead, Aperture stores this information in its library and attaches it when exporting versions in JPEG, TIFF, PSD, or PNG format. If you export the RAW masters, none of your metadata changes will come along with them. Unlike the issues listed above, this feature is by design.
If your goal is to archive RAW files outside of Aperture with metadata attached, you'll need a workaround to this aspect of Aperture's metadata handling. Because Aperture is designed to read added metadata at time of import (despite the current issue described above), the best long term solution (after issues are resolved) will be to add your metadata in Photo Mechanic (or similar) prior to importing them to Aperture and then refrain for the most part from using Aperture's metadata tools. If you don't like that workaround, a secondary workaround is to export JPEG versions to be kept alongside the RAW masters. To save disk space, the JPEG copies could be a minimal size.
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