If you watch movies where someone is carrying a candle or lantern and it goes out, do you ever notice that the candle goes out, but the light is a split second late to go out? That's because almost all of these scenes have supplemental lighting.
If you are holding the candle very close to the actor's face, you could probably see his face. To light a room, you're going to need other lights. I don't know if you've heard of china balls, but they have a light inside them and the whole ball emits soft, ambient light.
Another technique is to place colored gel sheets that mimick fire light and place a fan by them, so that the light has a flickering effect. This may be too loud to record the actual dialogue, but you could dub it, later.
Another way is to have the candle sitting on a white, gold or metalic base. Shine a tight spotlight down on the candle and the reflected light from the base will light your actors faces, from where the candle sits.
If you have a camera with nightvision, then the candle will be plenty. Depends on how you want it to look. I assume you're not shooting a GHOST HUNTERS episode.