Multiple problems with compositing

I’m trying to do a scene where a candle is on fire and the fire and smoke are done with 2.5’s smoke simulation. I also have the camera zoomed in far and am using defocus to make depth of field. Here’s the first test render:

(click images to enlarge)

As you can see, there are multiple problems here:

  1. The smoke system’s volumetric material doesn’t defocus properly
  2. The smoke system’s domain shows borders
  3. The depth of field is way too blurry, even though fstop is set to 127.999

Next, I created render layers to separate the foreground from the background, to fix the volumetric defocus:

As you can see, the results are much better, and I like that the smoke is more visible, but problems 2 and 3 still occur.

Next, I completely deselected the background layers from the scene, and simply rendered the foreground:

As you can see, now problem 2 is fixed, as the borders of the smoke domain do not render. I can render the background animation, and then the foreground animation, and composite them later, and that should fix the smoke domain’s borders, but I am left with one final problem, the blurriness of the defocus node.

Like I said, the fstop is set as high as it can go without being disabled: 127.999, and yet the blurriness is crazy. Obviously the zbuffer is working properly as the foreground object is still in focus, but the background is just ridiculously blurry. Also, decreasing fstop does make it even blurrier. I suppose I could work around this by decreasing the maximum blur, but I’m wondering why it’s doing this when I’ve seen people’s renders that have fstops quite low and still aren’t anywhere near as blurry as mine. Are there settings I may be overlooking? Here are my defocus settings:

Thanks for your help!

btw don’t worry about the quality of the objects or materials, I’m still going to tweak them later.

Preview? Try it off?

Where is your BG in relation to your point of focus (the candle)? If it’s very far in the BG of the scene, and your camera is very close to the candle, that may be contributing to the amount of defocus.

Scene scale may also (again) be an issue – if your scene is “micro-sized,” then that may exaggerate the defocus effect.

Both of these considerations also apply with traditional optical camera DOF, so that’s why I’m suggesting their applicability here.

Domain appearing really sucks tho’ thats a shame.

That’s probably it. The camera is actually far away and zoomed in a lot. That and my “micro-sized” scene are probably factors.

Oh well, actually, after looking at it a few more times, I think the extreme depth of field effect might help what I’m doing anyway. I wanted the fire and smoke to be the primary focus, and the background might have been too detailed, even with a smaller blur, drawing too much attention away from the smoke. This way, it still separates the candle from the scene without actually taking it out of the scene completely.

Long focal length lenses are notorious for shallow depth of field – not sure if this is a factor in the Defocus node, though, since Blender’s “Lens” setting isn’t a true focal length.

I think that I’d break down the effect as far as I could: candle, flame, smoke, background. I’d be expecting to do quite a bit of “nodes” work especially on the smoke, blurring it, reducing its opacity right around the flame and increasing it with a linear gradient, possibly a color change, and so on.