It's a documentary about a detailed look into a theory about how Dutch Rennaisance painter Vermeer created his masterpieces.
According to the theory, he combined mechanical means like lenses, mirrors and a dark room to invent a method anyone (without special training) can use to paint realistic images like Vermeer's paintings.
While there is no historical evidence of how Vermeer worked, Tim Jenison (an inventor and entrepreneur known for his work in creating software for television production) attempts to re-create the method, and re-produce one of his paintings. He builds an exact replica of the room Vermeer worked in, and uses tools available to Vermeer to paint that scene. He is not an artist, and has never painted anything in his life.
I found it fascinating.