Just as an update.
I was at the Monterey aquarium yesterday. I had both my sd1m and my xe1 w/ 27 pancake lenses. My intention was to use the xe1 in the aquarium and sd1m for the outdoor shots. Everything worked as planned until my Fuji 27mm died on me.
When I switched over to the sd1m w/ the 17-70f2.8 to4, even at 17f2.8, there were a lot of shots that would not lock af at all. The same type of shots that the Fuji xe1 would get af lock on. I even noticed a Nikon one shoot a burst of maybe 7 shots next to me one time while I was trying to get focus lock.
Of course there are places in the aquarium that are so dark, I noticed that guys w/ Nikon dslrs were not using them.. But instead chose to use their iPhone video instead.
So why did I not use manual focus? Extremely poor eyesight in terms astigmatisms that are not correctable even w/ hard contacts. I need mag view plus focus peaking to get correct focus..
Anyway, I looks like anything worst then iso 1600, f2.8, under 15th second, af lock is iffy. The Fuji had no problem there...
Anyway, the xe1 was my intended camera for the aquarium. It will be interesting to c what usable shots I get.
Gary