Camera with a lens with very shallow focus. You see this often with good cinema lenses, or some good still camera lenses on Canon 5D or C300 cameras. As for the slow motion...shooting a higher frame rate like 120fps or 200fps, and then slowing that down to 23.98 or 29.97 causes that. Add in Twixtor if you want to slow it down more (Plugin for After Effects).
Shane
Little Frog Post
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