I love auto ISO on my 40D. Being able to set the aperture and letting the camera figure out what shutter and ISO is great. Canon's system is really smart and knows what lens I'm using, and automatically adjusts the "minimum" shutter speed. Additionally I'm not much of a pixel peeper, and ISO 800 on the 40D is fine with me. When I'm shooting with strobes or in daylight I'll drop down to ISO 200 (100 isn't an option with HTP turned on), but the 400-800 range is good in cases when light isn't great.
So I'm getting that FF hankering so many people seem to get. I like low light, I like shallow depth of field, and I like wide angles. I think the real slam dunk for FF is that the L build 17-40 is cheaper than the (optically great) non-L build 10-22.
So I'm looking at 5D Mk II reviews, and saw something about the auto ISO, it looks like it goes from 100 (nice, I like that better than 400) all the way up to 6400.(!) Is this right? I know that high ISOs are much cleaner in the 5D Mk II than they are on the 40D, but I thought we were talking 1.5 stops, not 3 stops.
So here are the questions:
1) Do I understand correctly that auto ISO is 100-6400? Is there any way to adjust that range (I don't think there is on the 40D)?
2) Is ISO 6400 on the 5D Mk II as clean as ISO 800 on the 40D? If I'm perfectly happy with my low-light shots at ISO 800 on the 40D should I not be afraid of ISO 6400 on the 5D Mk II?
3) Do many (or most) other people shoot in auto ISO? Assuming Canon changed the auto ISO so that it operates outside of the "safe zone" that my 40D does, does that mean that other people don't use auto ISO as much as I do?