>Thanks Eric, Steve etc, for the explanation, except that if I
>take an image with my D700 in DX crop (which I've only done
>for experimental purposes) at ISO 1600 and cropped to 50%, the
>noise appears to be far less than an image from my D7000
>cropped to 50%. Perhaps it's just me or my eye sight, but
>could pixel density in the sensors vary noise wise, dependant
>on some other factors such as sensor manufacturers, processors
>etc?

>Richard

This is to be expected Richard (although I don't know about far less). I think Bill's chart shows a .75 stop advantage to the D700 over the D7000 at ISO 1600.

Jim