Originally posted by egordon99 Not to stir the pot, but my Canon 40D fitted with either my Canon 85mm f/1.8 or Sigma 30mm f/1.4 had no problems locking focus (using the extra sensitive center AF point) in a dimly lit room. As to how dim it was (going by memory here), I was at f/1.4-1.8, ISO3200 and getting ~1/30s.
So I wouldn't say it's a problem with "DSLR's in general"
I would be willing to say that your example is bright compared to some people doing 5-10 second exposures.
I also do low light work, but generally do manual focus when I do, because it gives better control.
For those who ask about split image, NO they will probably not work because they will go dark at those light levels.
Also as an after thought, autofocus works on contrast. If there is a lot of black in your image, then AF won'r work, and I don't care who's AF we are talking about because there is no contrast between 2 black objects.