I get confused by high ISO's. generally they just make my pictures a lot more messy I might go a little way up but I nearly always keep it as low as possible?
Am i right in thinking that high ISO's are best used only when you can't get a low enough F/stop aperture? I can see how in a dark setting like a stage could use it inc onjunction with a nice aperture so as to get a shorter shutter speed but still. I hear about people cranking ISo's up a lot and the noise terrifies me.
Is it just that different cameras are much better with high ISO's and mine is a bit lacking?
It's dependent on what camera you have and what it's internals are. Anything less than a full frame for digital will given you worse high ISO performance than a comparable full frame DSLR.
My D300 takes perfectly fine pictures at ISO 1000, anything after than and I start to get annoyed at the noise that appears but it's still very usable up until ISO 2000, but with prints, the noise becomes less of an issue since printers add their own anomalies and smoothing. Don't be afraid to bump up the ISO a bit, even if there's a bit of noise, most of the time you won't be showing the pics at 100% and reductions will mask a lot of the noise, if there is any.
People that use high ISO even with good light usually do it for super high shutter speeds paired with f stops of f8 or greater. I know a few people who do that and I've started upping my ISO a bit in the sun to get shutter speeds of 1/2000th and above for birds in mid flight. It works great. Don't be afraid to bump up the ISO, even if you do get a bit of noise, most of the time you're not showing people the picture at 100%. A reduction will take care a lot of the finer noise and post processing can take a limited bit of the rest out.