How do 1/3 ISO stops work in terms of noise?

12mnkys wrote in post #7730196
You can turn off the 1/3 Stops for ISO. It is in the Custom Function Menus. I can't recall which one, as I dont have my Camera in fron of me.

maybe I'm not looking hard enough, but the only thing I see that's close is "CF6- Exposure level increments 0:1/3 stop 1:1/2 stop" but that isn't doing anything to the ISO. There is also ISO expansion, but that only disables ISO3200 not the other ones.

DStanic wrote in post #7730260
maybe I'm not looking hard enough, but the only thing I see that's close is "CF6- Exposure level increments 0:1/3 stop 1:1/2 stop" but that isn't doing anything to the ISO. There is also ISO expansion, but that only disables ISO3200 not the other ones.

I just looked in the manual for the 30d and don't see it either. On the 50d, the ISO can be set to 1 stop increments.

DStanic wrote in post #7730260
maybe I'm not looking hard enough, but the only thing I see that's close is "CF6- Exposure level increments 0:1/3 stop 1:1/2 stop" but that isn't doing anything to the ISO. There is also ISO expansion, but that only disables ISO3200 not the other ones.

hmmm...i thought for sure I saw it...Let me look when I get home.

stellgar wrote in post #7729484
Maybe not always...read this and then compare 160 with 100 when shooting with xxd models. I have better results with ISO 160

http://forums.canonpho​togroup.com/showthread​.php?p=5225

That's an interesting chart - it lends to the possible notion that the "native" sensitivity of the sensor could be ISO 160 rather than 100 or 200.

I'd like to see a similar chart for the 5D2, 1D3, and 1Ds3.

40D it is Custom Fn 1 menu and go to #2. It gives you a choice 1/3 of 1 full stop for ISO.