Originally posted by Ira How does it help you?
Well, for one thing, I don't have to push-process like I often did with my K10D's ISO1600 limit. That saves me considerable PP time.
Also, images are much noisier shooting ISO 1600 on the K10D at -1 EV or -2 EV and push processing up +1 or +2 in PP to compensate. If I need ISO 3200, or 6400, or higher, I just use that.
It also often helps me get the shot. When I set the ISO myself, sometimes it's enough, sometimes it's not. If it's not, i have to take the time to chage it, and can sometimes miss a shot.
With Auto ISO, I can set Tv mode at 1/400, and if the exposure is such that the widest f/stop isn't enough to expose the scene properly at ISO 800, the camera pushes up the ISO to whatever is needed, without me having to stop, bump up the ISO, and try to get the sot (which by that time may have already passed my by).
Last, and I haven't been able to test this in a controlled setting, but it is an observation I've made: When using the 55-300 lens in Av mode, the camera appears to take the FL into consideration, and increases the shutter speed and ISO if needed. For example, if I'm set to f/5.6 at a FL of 70mm, the camera will meter and set the shutter speed accordingly. But if the shutter speed drops below, say, 1/40, the camera bumps up the ISO to keep the shutter speed at 1/6 or faster.
Likewise, if I'm with the same lens at FL 300mm, the camera bumps up the ISO as necessary to keep the shutter speed at 1/125 or higher.
Again, I haven't tested this last thing extensively in a controlled setting; it's more of an observation. I seem to notice that, when the scene gets brighter, I seem to get a combination of BOTH and increase in shutter speed, and a drop in ISO. The two factors seems to work in conjunction in Av mode.
In summary: Because the high ISO ion the K-x is so good, I often shoot in Auto ISO, with a top ISO setting if 8000, 10,000, or even 12,800.
I definitely do notice the NR kicking in at these higher ISOs, especially 12,800. But, if it's the difference between a blurry sot because the shutter speed was too slow, or a shot with some NR softness, I'll take the latter.
Greg