Originally posted by Nanthiel What about people moving? Even small movements and it's impossible to shoot it with f/2.8 flashless, isn't it? And as I mentioned, it's nice to have more than the eyes of one person in focus... so f/2.8 isn't an option, much less f/1.4.
I think you are greatly overestimating the effect of both issues. At ISO 1600 and f/2.8 you can get shutter speeds of 1/30" or more in "most" indoor environments. And actually, that's being pretty conservative - often, you don't need ISO 1600 to get 1/30", or you can get shutter speeds of 1/60" or better if you do go to ISO 1600. Sure, those kinds of shutter speeds won't stop someone who is actually running or engaged in other very fast motion - flash is needed for that - but nor is 1/30" so slow that it requires people to be perfectly still. It just requires a little patience and good timing and your part. Similarly, while DOF is indeed on the shallow side at f/2.8, it isn't so shallow that you can't get a whole face or two decently in focus.
In fact, I think that f/2.8 is a pretty much ideal compromise between DOF and shutter speed, and I use it a lot even when shooting with my A50/1.7. Although to be sure, the main reason I ever use the 50/1.7 is when the light is so low that I'm concerned f/2.8 won't be "fast" enough. But that's actually extremely rare. The only times when f/2.8 isn't fast enough are situations where the light is so poor, you are likely to get a very flat and uninteresting photo anyhow. Still, it's nice to have the *option* of going faster than f/2.8, which is why a lot of people like the FA35/2. But the size and focus speed of the DA40 is pretty impressive, and I for one think it's the single most useful length for candids on APS-C.
I have three primes I can use in these settings - M28/2.8, DA40/2.8 and A50/1.7. The 40 gets *by far* the most use of these for candids, and the three together cost less than the FA35/2, which would be the other choice I'd be considering if I were you (as opposed to DA35/2.8).
Here are some shots that demonstrate both why I like the FOV that 40mm gives but also that f/2.8 can provide both fast enough shutter speeds and great enough DOF - a practically ideal compromise: