Dearest All, hee hee. 1/ Angle of view on a lens specification, is that exactly what I think it means? And what does the diagonal angle of view mean? e.g. off the specs of the 20-70 /f2.8L Diagonal Angle of View : 74˚ - 29˚ (43.2mm) Haha, what on earth is the range? I find it easier to visualise how "wide" a lens is in terms of it's angle, but I'm not sure what I'm looking at. 2/ Is there some sort of conversion (an equation maybe?) that relates ISO increases and how much um, better it will work in less light? Or does the question not make sense? e.g. f/2.8 -> f/4 = half the light. Is there something like that wrt ISO? And is there a reason ISO goes up in doubles? Or am I mistaken haha. Thankees!