I just read a comment on a forum saying that the Canon 70D, when set to Auto ISO only chooses ISO's in one stop increments. So for e.g. if ISO 800 is not enough, it will jump to ISO 1600, and will not select ISO 1000 or ISO 1250 in AUTO ISO. Similarly if ISO 3200 is not enough, it will jump to ISO 6400 and will not use ISO 4000/5000. (Assuming you have set max ISO to 6400).
I would think that by setting ISO increments to 1/3 stops (C. Fn I-2, page 365 of 70d user manual) ISO will increase in 1/3 stops, even in AUTO ISO. Can 70D owners kindly confirm this for me ? I don't have one, but am considering buying one and AUTO ISO is a part of my shooting style.
And yes - I know if I have a problem with higher ISO's I can use Manual ISO and all that - as I mentioned, it's a part of my shooting style and I want to keep it that way.