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Most moviegoers have encountered the split diopter before. Whether or not they point at their screens like Rick Dalton and compulsively blurt out “that’s a split diopter!” every time they see one is probably less likely. Be warned, this is the trade-off: once you learn about the split diopter, seeing one in the wild will feel like Christmas. But not everyone will understand your excitement. If that sounds like a good deal to you (and it should), buckle up.
Split diopter shots are achieved with a special lens: a piece of convex glass that effectively renders half of the lens nearsighted while the other half remains farsighted. This single film element creates the illusion of deep focus by keeping two subjects at different distances in frame simultaneously. The trick to sussing out whether a shot uses deep focus or a split diopter lens is to look in the space between the two subjects. If the depth of field is continuous, you’re looking at a shot with deep focus. If you see a fuzzy line between the two sharp subjects, you’ve got a split diopter and you can open the champagne.
But these things are better seen than described. Luckily, the video essay below from Fandor efficiently lays out the history and technical mechanics behind the split diopter.
You can watch “SFX Secrets: The Split Diopter Lens” here:
Who made this?
This video essay comes courtesy of Fandor. The San Francisco-based indie-film streaming service/blog/video essay heavy hitter closed shop in 2019 after, you know, laying off their staff and restructuring their assets to a third party. If you pop over to Fandor’s website you can see they still, uh, exist. But their social accounts and YouTube account haven’t been active for over a year. Luckily their video essays are still free to browse.
More Videos Like This
- Here’s PBS Digital Studios’ Shanks FX with a more-hands on demonstration of how a split diopter lens works
- Another from Fandor: “The Art of the Focus Pull“
- All fifteen of the split diopter shots in Blow Out
- Here’s Filmmaker IQ with the science behind deep focus and hyperfocus distance
- Woah, woah, woah, wait a minute…what’s hyperfocal distance?
- The Nerdwriter has a fun video on the real fake cinematography of Toy Story 4, an animated film that has a “split diopter” in it
- Got 45 minutes to burn? Here’s Brian De Palma’s Film Society Talk at the Lincoln Center