Exposure basics, lesson two point one (& ISO)

Rather than kick this off in a specific direction, at the outset, I'll just open this as a place for us to continue the discussion that started here:

and continued here:

Exposure basics, lesson two

Both of those discussions have reached 150 posts. Rather than kick this off with a specific theme, I'll leave it open and let those who are interested pick it up in the replies.

tex