The camera Luke is using is a Yashica Electro 35. This is a rangefinder camera. When we see Luke lying in bed at the end of the movie looking through the lens and focusing at the ceiling above him the image is first blurry then sharp. The mechanism of a rangefinder camera is different from that of a SLR camera. You don't focus by making a blurry image clear but by bringing two overlapping pictures together.
One minor error: in the film's end credits (on DVD), Roben Sullivant is mistakenly listed as "Luke's Mother," when she actually plays--as correctly indicated on IMDb--"Jonah's Mother." In fact, Luke explains early in the film that his mother is dead.