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Wikimedia Commons // Public Domain

August Musger: The Priest and Physicist Who Invented Slow Motion

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Wikimedia Commons // Public Domain

Pretend you’re the director of a movie. You want to indicate to the audience that something important is happening. Maybe your hero is facing off against his or her mortal enemy for the first time, or is reuniting with a long lost love after many years. Naturally, there are a number of cinematography techniques at your disposal, but should you choose slow motion, you'd be in good company; it’s a favorite technique of filmmakers like Akira Kurosawa, Sam Peckinpah, John Woo, and Wes Anderson.

Of course, time isn’t literally slowing down for your characters—it just feels that way for the audience. There are a few different techniques that a director or cinematographer can use to accomplish slow motion, each of which probably strays very far from what August Musger, the original inventor of the effect, could have imagined.


August Musger was born in 1868 in Eisenerz, an old mining town in Styria, Austria. A gifted student throughout his childhood, he graduated from the Faculty of Theology and was ordained in 1890, after which he spent two years serving as a Kaplan, or a priest’s assistant. He began studying mathematics, physics, and drawing in Graz during this time, eventually becoming a teacher of these subjects in 1899. When he wasn’t teaching, he was likely taking in a film.

In the early 1900s, motion pictures were a relatively new art form. Not much time had passed since one of the world’s first movies, the Lumière brothers's L'arrivée d'un train en gare de La Ciotat (1896), allegedly sent audiences screaming out of the theater, but motion pictures were becoming a popular pastime. The first “nickelodeon” opened on June 19, 1905 in Pittsburgh, Pennsylvania, allowing scores of people access to the cinema for only five cents a pop. By 1907, some 2 million Americans had visited a movie theater.

Still, the technology was primitive. Projectors used intermittent motion, in which a mechanism held a frame of the film in place for a split second before the film advanced. The hand-cranked machines had shutters that blocked light and caused flashes of darkness between frames, which was necessary to trick the eye and brain into seeing motion. If all was operating smoothly, and the cranking was moving at a consistent rate of around 16 to 24 frames per second, the flashes would be imperceptible to the human eye—but they became apparent when the film was moving slowly. Because the projectors were cranked by hand, the frame rate was highly variable, causing movies to flicker and jerk. (That’s one theory for why we call movies “flicks.”)


Musger thought he could fix the flickering by creating continuous motion—or having the film move with the shutter open—within a projector. It was easier said than done. Just playing film without the shutter made the projected image blur, so he developed a method of “optical compensation” for the movement of the film. To do this, Musger divided a dark chamber into two areas: In one was a conical lens, a wheel of mirrors, and a rotatable prism; in the other were the rollers that, along with the wall, guided the film strip.

During projection, a light source placed outside the apparatus shone into an opening (n) designed to allow light to enter. The light illuminated a frame of film (e) that was exposed by a gap (d) in the wall along which it ran, projecting that image onto a mirror on the rotating mirror wheel (c). The image bounced off the mirrored wheel onto an angled mirror (located at u) that projected it through a lens (b) and onto the surface where the film was being viewed. Rather than using a shutter to block the light in between frames of film, as in intermittent motion, Musger’s apparatus fed the film continuously, using wheels that rotated at the same speed as the mirror wheel. The mirrors from the wheel caught the images from the film and threw them onto the angled mirrors, which projected them onto the viewing surface. Each mirror on the wheel reflected one image, which was replaced by the next image as the mirror rotated and the film progressed. The angled mirrors worked to flip the top and bottom portions of an image when one frame was replacing another, so that the picture always remained right-side up to the viewers.

Musger patented his device—which could also shoot film—in 1904 and demonstrated its projection capabilities for the first time in 1907 in Graz (where Musger lived) on a projector made by K. Löffler. After the demonstration, Leopold Pfaundler, a professor and a member of the Board of the Physical Institute, wrote that Musger’s device was “theoretically correct and has also proven to be useful in the samples taken at the physical Institute. Any extant imperfections, which exist with the first model, will be easily remedied by small modifications.”

Musger’s complicated projector did create a small improvement in the flickering, but it had an unintended side effect: By shooting at 32 frames per second—twice the normal speed—during recording and playing it back at a regular frame rate, he could create slow motion.

The inventor didn’t see this as a selling point for his apparatus, though, and didn’t seem aware that he had created something unusual; he mentioned his device’s slow motion capabilities only in passing in the patent, noting that “all movements are continuous and without impacts, that no moment of time is lost for the recording, and that the number of recordings possible in a second becomes a significant one, which may be particularly advantageous for scientific purposes.”


With a public demonstration and a favorable review under his belt, Musger went about improving his invention. In 1907, he submitted a patent on the improvements. At the same time, he founded Prof. Musger Kinetoscope GmbH in Berlin to build and sell his projector, expanding the business to Ulm in 1908.

Sadly, Musger wouldn’t get far in his endeavor. His projector was plagued by technical difficulties, and though he had conversations with Zeiss, Messter’s Projection, and Steinheil & Sohne, he couldn’t convince any of them to invest in his technology. Financially ruined, Musger couldn’t pay the fees to keep his patents and lost them in 1912.

Waiting in the wings was Hans Lehmann, a technician at Ernemann and a man to whom Musger had been writing about his apparatus for a year. Lehmann took Musger’s idea and improved upon it, creating a slow motion system that he presented to the public in 1914. 

The Zeitlupe (from the German words for time and magnifying glass), as he dubbed it, was then sold by his employer, the Ernemann company, specifically as a slow motion recorder and player. Like Musger, Lehmann thought slow motion was a means to observe the previously unobservable—more for scientists than for cinematography. In a 1916 article for the German periodical Die Umschau, Lehmann recommended the technology to sculptors, military trainers, and gymnasts, so that they could further their craft by studying, in slow motion, movements typically too fast for the naked eye.


Lehmann never publicly acknowledged that his device was based on Musger’s work, though he did admit it privately to the priest in a 1916 letter. “I would be delighted to be able to show you the progress [of technology] based on your invention,” Lehmann wrote, noting that his device “might be called ‘Zeitmikroscop’ (because it increases the temporal length of rapid movements that the eye can not follow at the natural speed).” Musger never profited financially from the device Ernemann sold.

Despite his failures, Musger wasn’t yet ready to give up on cinematographic inventions. In 1916, he filed another patent application in Austria and Germany for “Kinematograph mit optischem Ausgleich der Bildwanderung,” or “Cinematograph with optical compensation of the image migration.” The layout of the device differed significantly from his first cinematograph, and had two rotating mirror wheels. But Europe was in the midst of World War I, and the poor economic situation prevented Musger from building the new device. Eventually, the idea of continuous film would fall by the wayside as well, when camera operators realized that by “overcranking” or cranking the camera at a faster-than-normal speed, they could capture footage that was good enough for their purposes.

Musger passed away on October 30, 1929 in the Prince-Bishop’s minor seminary in Graz, without seeing the effect his invention would have on the film world. But if he were alive today, he’d probably be happy that slow motion is one of the most widely used cinematography techniques.

Additional reporting by Jocelyn Sears.

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iStock // Ekaterina Minaeva
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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