The following shots are with a small white light throwing "emergency light" on a height of one and a half forearms.
I used 3 candles on left side and 1 candle on the right.
Used 3 candles on right side.
Used 1 candle in the center, and 3 candles somewhat far on a stool.
Where to place how many candles to avoid noise?
The shots are from Nikon D3100, with ISO 200 at F1.8.
I don't think these pictures are particularly noisy, although there is some in the shadow areas. While digital noise isn't as attractive as film grain, I think that in many ways it adds to the aesthetic appeal of this kind of low-light photograph. It's part of the vocabulary of photography, and we expect to see some.
If you do want to make the image as noise free as possible, as Matt Grum often tells us, don't be afraid of high ISO. This will give you a better signal-to-noise ratio for the same image exposure value.
Also, one of the reasons digital noise is less attractive than film grain is that it tends to produce colored speckles. That's one of the reasons I suggest converting to black and white in my answer to Is it practical to shoot portraits by only candlelight?. However, I don't think chroma noise is a big problem in your photograph, so if you like the black and white, it might be largely for other reasons:
That loses some of the warmth of the color version, though.
As an aside, I think you've focused a bit too closely in this image; I'd rather see more of the candle in focus. If you increase the ISO, you may want to also consider stopping down a bit for greater depth of field, although that's clearly a stylistic choice. I'd also really like to see more detail in the flame and in the area right around the flame — but that's off topic for this question and right back to Is it practical to shoot portraits by only candlelight? (or maybe a separate new question on candle flames themselves).
