Preview's raw colour management

If I open a NEF in Preview it will allow me to save out a TIFF tagged with the AdobeRGB profile. There are some colours in these conversions that I like but I can’t seem to match them in Capture One 9 (and I definitely don’t want to use Preview for the conversions). Anybody know how Preview handles colour in raw conversions? Or have links to documentation? -- Martin Orpen Idea Digital Imaging Ltd