As the conversion to digital projection continues to transform cinema exhibition, much of the enduring imagery of movies — reels, film, a booth, a projectionist — is fast becoming obsolete.

That’s one of the reasons that Boston filmmaker Peter Flynn is making a documentary about cinema projection, traveling the country to big-city and small neighborhood theaters, visiting booths and the projectionists inside them. His film, “The Dying of the Light,” endeavors to, as he puts it, “capture the craft of film projection at its moment of eclipse.”