an ode to the split diopter

the thing about split diopters is people either love 'em or hate 'em, and i'm on the side of loving them. the enemy seems to find them hokey and visually jarring (why don't they just use deep focus1 or a focus pull2 blablabla) and i won't disagree in certain cases, but that doesn't stop me from thinking that those very disadvantages can be used in a way that makes narrative sense, thinking they're technically very cool, or having fun spotting them while watching movies. what is a split diopter? a split diopter lens is a half piece of convex glass that you attach to the main lens of a camera. this makes one half of the lens nearsighted and the other half of the lens farsighted, similar to a pair of bifocal glasses. the split diopter lens is what focuses on the foreground. what separates split diopter shots from the average deep focus shot is that they show the area between the two subjects out of focus, creating a particularly harsh blur line right down the center. this blur line is…