Is there a way, possibly using exiftool, to quickly search an entire directory or disk of images for a certain exif/XMP/IPTC tag and maybe even give a summary of what the collection contains (percentage of empty tags, some example values, that sort of info)?
The reason I am asking is because I am working on moving very large collections of images between systems and I have to transform the metadata. So I want to be able to analyse stuff quickly to discuss it with the client. Lightroom, Aperture and co. are nice, but not installed on the systems we are working with and importing would be much too slow anyway.