Killer of Sheep, Charles Burnett’s legendary low-budget 1977 feature shot on the streets and in the houses and apartments of Watts in Los Angeles, has that marvelous capacity among motion pictures: it sneaks up on you. Much of it is deliberately understated, just-folks filmmaking (it was shot over the course of a year, for less than $10,000), but the frames often hold deep significance, especially in combination with the film’s soulful song score.