Hi,
Lobone said

The only problem with auto ISO is that the camera doesn't really know what subject you are photographing. It can pick an extremely high ISO giving you a photo with allot of noise. While auto ISO is probably O.K. in a pinch it is a better idea to preset your ISO and control the photo with aperture and shutter speed adjustments

Well, actually, the point of "Auto ISO" (TAV) is so you don't need to commit yourself to an ISO and miss a lot of shots because your shutter speed wouldn't stop a snail. If you're not concerned about shutter speed and aperture, then, of course, you wouldn't use TAV.

I don't know about other cameras, but the Pentax lets you set the meter to read the same area as you've focused on. If you set the AF dial to "spot" and, in the menu, tell the camera to link AF with AE, you're all set. You can "lock AE" when you "lock AF" by pressing the shutter halfway down.

I've shot literally hundreds of exposures using "Auto ISO" and they've been correctly exposed because the meter read what I told it to. It would not pick a needlessly high ISO unless I focused on the wrong place.

I don't advocate TAV or "Auto ISO" or whatever as a good "default" setting.

Have fun,
Steve

Canon G9 has two "auto ISO" features. One (ISO Auto) adjusts ISO in a narrow range: 80-100-200. The other (ISO HI) adjusts it as high as 1600, I believe. I steer clear of the latter setting because of the extreme noise that appears on images shot at 400 or higher on this particular (non-DSLR) camera.