Hmm. Interesting. gThumb already knows the mime type of the file when it wants metadata. Could the known mime type be supplied to exiftool as a parameter to speed up processing (ideally exiftool would quickly quit if it didn't recognize the specified mime type)?

I could add an array of mime types that exiftool is known to support, but then I'd have to manually update the program each time new file support was added.

We'd have to agree on mime type names for RAW files - I'm not sure if they are all standardized (some are).

- Mike