You can use candles for lighting accents, but it will be difficult to adequately light the subject using only candles. If you'd like to see how hard it is to do it correctly, look at Stanley Kubrick's film "Barry Lyndon." Note how many candles were required to light the sets and close-ups - you'll rapidly lose count as there are hundreds if not thousands.

Kubrick did not use any supplementary lighting on this film for the interior scenes - only candles. He did use a specially modified film camera so he could use a very fast aerial photography lens, and shot wide open with it.

I would suggest the following. Use hot lights (tungsten or tungsten halogen) if possible. You can make snoots for the lights using heavy duty broiler foil and just fitting it to the front of the lights. What you are trying to do is get the lights as directional as possible to use for accents.

Light the overall scene as evenly as possible to an overall low level using bounce light from reflectors. Establish a 2:1 ratio so you have a "shadow side" and a "highlight" side - but again at a low level lighting level like about Zone IV on the highlight side and Zone III on the shadow side.

Put your candles into the scene and see what they do and now start adding additional lighting using the lights with snoots on them. You can attenuate the light by using "angel hair" (non-oriented fiber glass cloth). You should be able to find the cloth at most home improvement mega-stores along side the Bondo polyester resin.

The cloth is non-flammable, won't burn-up and you can add it in layers as needed to attenuate the light as it exits the snoot. You will probably need at least one light down low shining up so that it looks like the candle is providing the illumination. Add other lights as required until you get the look you want.

If you are shooting in color, shoot tungsten balanced film. You will have the problem of color balancing the candles (about 1800K) with the tungsten lights. The tungsten will actually be "cooler" (bluer) at 2500K to 3200K depending upon the type of light. You could gel the lights down to match. Or, you could let the lights just be whatever they are and let the candles be slightly redder.

If you are shooting black and white, then of course, you won't have the color balance problem.

The suggestion to shoot day-for-night is interesting, but takes a bit of experimenting to get correct. In color, the standard day-for-night exposure is to simulate a soft, underexposed bluish effect. This is usually done by underexposing 1-1/2 to 2 stops depending upon the film type. The bluish cast is sometimes added during printing of the release print or by filtering slightly. The problem is that the blue will often turn skin sort of a copper/purple so you have to be really careful with filtering. A somewhat different approach can be taken by trying to simulate "warm moonlight" with the addition of a light yellow (CC10) filter on the camera using 3200K lights and matching 3200K film. Or a "straw" filter (color) on the lights and no filter on the camera.

Black and white is much easier using a Wratten 23A and a Wratten 56 combination (Harrison YL-7). The 23 + 56 is usually used with a filter factor of 6 rather than the 20 required for total filter compensation (5 for the 23A and 4 for the 56: 5 x 4 = 20). This automatically achieves the 1-1/2 stop under exposure.

However, not all films have the same filter factor with all filters - everything given is the starting point only, you have to experiment to find out exactly how the filters will work.

That's the short of it....