It's exciting when a presenter sets out to cast new light on an old film. Of course, there's nothing wrong with an introduction that explains a movie's production history or shares some pertinent facts about the filmmakers. But a novel thesis can force you to adjust your perspective before the projector rolls. It's a bit like putting on a pair of 3-D glasses—small details jump out at you unexpectedly and the relationship between foreground and background (or between content and subtext) seems to have been magically altered.
To cite a recent example, at last month's book-release party for Rob Christopher's movie guide Queue Tips, local writer David Kodeski presented an entertaining talk about "hand acting" in 50s and 60s Hollywood melodramas. He pointed to scenes where actresses appear to express unsimulated passion for their male costars in how they grab their chests, backs, and thighs. (Had he broadened his scope to consider American movies of the 1970s, he might have touched on the first love scene from Shaft.) Kodeski argued that these moments carried an inadvertent gay subtext, with authentic desire for male flesh hiding behind the screen of inauthentic drama. I'm now looking forward to watching the Susan Hayward version of Back Street, a movie I never would have wanted to see otherwise.
But that's what good introductions do: they make you want to see more.