I don't understand you guys regarding this ISO and noise issue.
I downloaded the image and looked at it in PS. My estimation is, that the darkest part of the underside of that grayish-brownish roof is around the 5th EV of the dynamic range. (The railing is too small to judge anything on it.)
Now, even if the camera does not have ISO 1600, not 800, not even 400, this area would be between the 8th EV at ISO 200. Is *that* expected to be noisy with a Hasselblad back? Is the dynamic range of this back 9 EV at ISO 200? And then we have not even mentioned the ISO gain (assumed, that ISO 1600 is real, i.e. it is associated with a specific analog gain).
The high ISO capability has to be judged (if not measured) on the *shadows*, not on well-lit areas.
Although I find it highly suspect, that higher ISO will be introduced by *firmware*; that must be some miraculous firmware. I suspect this ISO 1600 is simply a shortcut for +1 EV in the raw processing, while the real advantage is, that the in-camera display gets brighter than it would be with the underexposed ISO 800.
Is the raw file of this shot available in DNG format?