5d2, Aug 19 nightly build (2015Aug19)
When I attempt to select Dual-ISO 100/1600, 100/3200 or 100/6400, I see the warning message:
"Consider using a less aggressive setting (e.g. 100/800)
The 5d2 seems to accept 100/1600, and shows 2.8 EV DR gained.
However, if I select 100/3200 or 100/6400, it seems to ignore those settings. The EV gain doesn't change. When I return to the higher menu, it continues to show 100/1600 rather than 100/3200 or 100/6400. When I "Q" back to the Dual-ISO pop-up, it does show 3200 or 6400 as the upper ISO.
Am I doing something wrong? Is this "as expected"?
IIRC, I used to be able to select 100/3200 and 100/6400 on the 5d2. I think the 6d implementation allows 100/3200 and 100/6400.
ISO 3200 and 6400 are not CMOS (analog) ISOs on 5D2. Therefore they have no affect on dual ISO (which is a manipulation of CMOS gain registers). The CMOS analog gain registers do not even change going from 1600 to 3200 or 6400 (it's only downstream electronics that are changed or digital manipulation to get those higher ISOs)
The 6D is different and has higher analog ISOs available.