Autofocusing in the dark

500d does, it's under "Custom Functions".

I use a 430EX II and a 550EX on a 60D. I can focus on my cats in the house in the middle of the night with the built-in focus assist. It can be so dark that all I can see is the outline of a cat in the shadows and I can get a perfect shot, with flash of course. Get a flash with focus assist.

Hardrock40 wrote in post #14770944
550d has bbf? not to sure about that.

It doesn't have the dedicated button but you can reassign one.

The AF assist beam on the 430 EX II is great. Perfect focus even in pitch black, or against low contrast targets like a blank wall.

If this is something you are doing a lot of and the distance is great you can look at a laser sight for $40.00 to $50.00. Killjoy demonstrated this at a POTN meetup about a year ago.

I do lots of cave photography and have used a variety of techniques to assure that the image is in focus. you can use a flash with focus assist and you should change to a single focus point. The other thing that you can do is make use of the hperfocal distance.

Hardrock40 wrote in post #14770944
550d has bbf? not to sure about that.

Sure it does.... custom functions can reassign the exposure lock button.