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Unfortunately you can't take any photos that's above 3200 ISO with the 1Ds Mark III. It's native ISO only goes up to 1600. There is a software mode that'll take it up to 3200. The 3200 ISO of the 1Ds Mark III is very useable. I would say it's close to the 5D Mark II at 3200, but a little noiser.
I love my 1Ds Mark III!