There is an ISO question buried deep in another thread and so I thought I'd bring it up out here.
Please correct me if I'm wrong, but I thought there were some ISO settings that were just better than others in regards to digital noise and compression?
I WISH I had bookmarked the thread, but I thought I read somewhere that 1600 was actually better than 1100 due to the way the software/hardware reacted to the setting???
The only reason I remember this is because I was surprised you could get a better picture by upping the ISO.

ARE there any "rules of thumb" to follow when choosing an appropriate ISO? Because if what I'm remembering is right, "lower is not always better."

Matt: Search Jon Fairhurst's threads, I think he did a post on that about a month past, when the issue came up. I think there was a discussion about some people representing that 1200 ISO was better than lets say 800, because of other technical issues. Haven't followed it, but I recall it.

I posted something here as well, including links to 3rd party photos, but I don't recall the thread name...

Was it this one?

http://www.dvinfo.net/conf/canon-eos-5d-mk-ii-hd/237031-neutral-density-filters-5d.html

Specifically this post: http://www.dvinfo.net/conf/1156349-post11.html

That's it! And this particular post has the link to the 3rd party photos...

http://www.dvinfo.net/conf/1156349-post11.html

Those tests were done by taking photos with the lens cap on & are of pretty much theoretical interest only. In practical use the difference in grain between say 100 & 2400 is all but imperceptible.