D4S since that's appropriate only from hitting photos for pro photographers who make their dwelling. Determined by how dim the backdrop is (deeper generally = better) it's likely you have to dial in some exposure compensation to get your bokeh to actually place. Next, try getting an interest how to blur background with a kit lens of some kind facing the camera at the minimum concentration length (or there about) using the bokeh shows in the background. It'll have a little experimenting with material and lighting (both forefront and background) however in virtually no time you should be filming bokeh just like a master!
For the novice, the aperture will be the starting within the lens that controls the total amount of light that makes it through shutter and the contact to the video/warning. Quick lenses below f/2.8 like my 20-year old manual-focus Pentax-A 50mm f/1.7 SMC are ideal for capturing bokeh (and is the contact I take advantage of for many of my bokeh pictures on Fickr). I've found that the quicker the emphasis range for the forefront issue, the higher the background bokeh I will get.
After I took this shot I had been at the minimum focus distance for my 50mm 1.7 lens (about 18-20″). The bright (gold colored below) spark lights were on another Christmas tree about 8-10′ behind the bulb and branch I dedicated to. Another smaller bokeh that is colored highlights were from additional lights on exactly the same tree that I focused on. Now that I've rambled about all catching bokeh's complex details on ad nauseam, let's where you truly move take action can get on towards the part!