I have the 350d and assume it should be the same on the 400d
If you're in Tv or Maunal if you click past 30s then it should go to bulb which basically means open as long as you hold the shutter open for. Obviously this should be done with a remote shutter release to avoid shake.
If you use bulb, your gonna need a wireless remote, as when you press the shutter you'll move the camera and get a blurred shot. Get a wireless remote, click one to open the shutter, click again to close, the distance between those two clicks is as long as you can bear the cold for
I've just bought a wireless one, but in terms of my question, whatevaaa!
If you go in to bulb mode, do you press to open the shutter and then press to close it? I'm assuming that's the case and you don't sit there for say 30 minutes holding the shutter open?!