Judging from the video, the resolution / dot size is about 1 µm (one micrometre). For comparison, the thickness of the tape in a 120-minute compact cassette is 9 µm, the diameter of a typical bacterium is 1–10 µm, and the diameter of the nucleus of a typical eukaryotic cell is 7 µm (http://en.wikipedia.org/wiki/1_micrometre).