Here’s another effect using YafaRay’s render engine and the 3D modeling software Blender ver. 2.64a.
Using photon mapping at 64 samples, and a depth of field (bokeh effect), it rendered 8hr 54min. on my Mac mini. I guess, the depth of field takes time to render in YafaRay at a size of 1536 x 864 pixels, but in normal rendering it takes less time.