I just used my Sony at kids' B'day party in a very darkly lit huge place (one of these places where they put on glowing sticks and jump on huge inflatables). I brought the kit lens, an external flash, and SEL50F1.8. Well, I forgot that SEL50F1.8 does not play well with moving subjects in low light... it produced some stunning photos out in the open, and decent shots on kids who stood still, but completely failed on running kids - the AF simply couldn't pick focus at all, by the time it acquired focus the subject moved. Zone focusing wouldn't work well either because it's very hard do prefocus in such a dark place. Kit lens didn't shine either, there was just not enough light. Flash helped a bit, but it doesn't do much difference if the camera can't focus in first place. Sony beats my old Canon DSLR in low light as far as the sensor performance is concerned, but the focusing is not as good, at least on moving subjects in really low light. Part of it is on-camera focusing, and big part is lens. At a similar party last year, I got quite a few more keepers with T3i, as both the camera and the lens could keep up with running kids in near complete dark. Of course I can't do much about in-camera AF. But I am wondering if perhaps I should've brought Sigma 30/2.8 along. Or should I tried to use a MF lens and prefocus ? Or, is there a e-mount lens that's known to have fast accurate focusing in low light ?