A baffling answer in today’s New York Times crossword, 32-Down, “Silent film effect”: IRISIN. Even after getting it, I was lost: was irisin a chemical used to treat film stock? No, the answer is iris-in. An explanation:
Iris: A technique used to show an image in only one small round area of the screen. An Iris-Out begins as a pinpoint and then moves outward to reveal the full scene, while an Iris-In moves inward from all sides to leave only a small image on the screen. An iris can be either a transitional device (using the image held as a point of transition) or a way of focusing attention on a specific part of a scene without reducing the scene in size.
Here is an iris-out, from Buster Keaton’s Neighbors (1920), found here. Please imagine that it is an iris-in.