Maybe someone knows the answer to this? It appears that ISO 160, 320,640 etc are the native ISO of the 60D and are considered quieter than other modes. Thing is though, what about ISO 100? Most places seem to recommend using ISO160. Is there a loss of DR if using ISO100 (ie is the camera using negative gain as it were)?

Hi. I asked a similar question earlier this year and here's thread link:

http://www.dvinfo.net/forum/canon-eos-5d-mk-ii-hd/484059-clean-isos-focal-length-applications.html