I find one of the major disadvantages with the DSLRs to be focusing in dark situations. With 35mm cams, there was the prism focusing aid. With dslrs, the autofocus doesnt work in the dark, and its extremely hard to see if your subject is sharply focused or not. What do you do to assure your image is sharp when you are working in the dark?
welll, if you have numbers on your lens, you can focus by guessing how far you are from the subject and dialing that number in.
I almost exclusively had to do that with old manual focus SLRs because of my vision.
A fast lens helps with AF in low-light though, since the AF system works with the widest aerture.. I've had no problems with getting a focus lock in low light with my 50mm 1.8.
Are you talking aobut shots with people or shots outside at night, if its the latter I bring a good flashlight and point at what I want focused then lock the focus or put it on manual right after I focus.
I try a few things (I don't have a DSLR, but it's the same problem with point-and-shoots):
1) Light up the subject with a flashlight, overhead lights, etc. until you get AF lock, then switch to manual focus and kill the lights.
2) Try focus bracketing if you've got it. Works just like exposure bracketing - focuses a little in front and a little behind.
3) If narrow DOF isn't important, use a smaller aperture (larger F number) so the precise focus isn't so critical. Of course, that leads to longer exposures, which typically means more noise. So this is a tradeoff.
There you go... but not for the reason you think. At least some of the Canon flashes have AF assist lamps built in (infrared) that help low-light AF regardless of whether the flash is set to fire.
Of course, another option, perhaps not as palatable, is to buy a 5D ;-)the darn thing focuses in almost any light imaginable.
