my 5d doesn't have it but the mark ii does

is it even useful?

I can't really think of any use for it.. Unless you are in a situation where the light is changing in extreme amounts extremely quickly..

This. Even then, with practice, you ought to be able to recalibrate your settings in less than 3 seconds.

and what do you do in a club where the light can change in 0,3 sec? Can auto ISO be useful there if I want to have constant shutterspeed and constant apperture?

yes. i would love auto ISO on my camera, i would use it over AV mode(that i use pretty much all the time)

See, now I have no use for the Auto ISO on my camera, I always use the AV when I don't have the luxury of time to use manual.. I just make sure I set my ISO so that my shutter speed never drops below what I need. I enjoy consistency.

Nothing exciting will happen within the 0,3 seconds because human movement isn't that fast. Not only that, but your reaction time would not match the time frame. It's useless to create such a scenario. And no, auto ISO would not be useful, since the camera's internal light meter isn't very accurate in places like nightclubs. It goes crazy with all the lights.

This post was edited by onepagememory on Apr 2 2011 09:05am

just asked this because I was curious how party photographers can make some really nice pictures under such conditions

They expose really well, often use several flash units, and if it's an award-winning photo, it's likely planned.

when I need to crank my iso up, and I still want control over aparture, I use manual mode combined with auto iso. This is great with zoom lenses imo!
I adapt the shutter speed depending on focal length, and I use the aparture I feel that I need, then I let the auto-iso do the rest. This gives me the lowest iso suitable for my current settings!

I use a d7000, I find auto-iso very useful.

This post was edited by Fil on Apr 3 2011 09:10am