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Seeing things in slow motion


50ms tube: How the brain perceives motion
Walter Murch Film-maker
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He limited himself to this particular analysis, and it's a very interesting article if you read it, it appeared in 1976 in Scientific American. But it made me think that perhaps this was also responsible for 'the phi effect' or 'the persistence of vision', the illusion in that we show you a frame, a still frame, and then we replace it with another, the first one, when you, the instant you see it, it is stored in this cache of some kind, this RAM memory, in great detail, waiting for anything that might happen within the next fifty milliseconds that it would be good to compare this information with, and sure enough if something comes along to compare it with, the brain synthesises something out of the information that's in this tube, this fifty millisecond long tube. There are two things in that tube and it's good to compare them and extract some meaning from that. Well, it turns out that these two things are slightly different, because in the second one, there is motion displacement, and as a result the mind constructs something that doesn't exist in either of these things, but is the mysterious sum of them, on another conceptual level, which is motion.

In very much the same way that we construct three dimensions out of the differences between the left eye and the right eye. As I look at you with my left eye I see some image and the window behind you is some displacement. If I look with my other eye, the window behind you is slightly differently displaced. So the two images, which are perfectly flat, are compared by the mind, and some other meaning is extracted from them, which is the world in three dimensions.

In some strange way, it's similar to the synthesis of red, the colour red, from the different signals from the three cones in our retina. And, there are, you can take this idea and run with it, as I have over the years, the, our hearing, human hearing kicks in at twenty cycles per second, which is a very low note, but we still perceive it as a note, as music. Below that, we no longer hear music; we hear the individual pulses out of which the sound is made. But started at about twenty, we hear, I'm not able to do it, but a note several octaves below that. Up until we run out of hearing at twenty thousand cycles per second. Well, the question is: why does hearing kick in at twenty cycles per second? Well, I'm suggesting because twenty cycles per second is fifty milliseconds. So the distance between the peaks of the waves is fifty milliseconds. If it's lower than twenty cycles, then the peak of one wave is already out of this [cache] tunnel or tube before the next one comes in, so we can't synthesise the two things and extract meaning out of them, and instead we hear each individual wave of sound. In the same way that if film is slowed down below the threshold of motion, we see individual frames, we start to see flicker, which is the equivalent of hearing the thumps of the frame.

Born in 1943 in New York City, Murch graduated from the University of Southern California's School of Cinema-Television. His career stretches back to 1969 and includes work on Apocalypse Now, The Godfather I, II, and III, American Graffiti, The Conversation, and The English Patient. He has been referred to as 'the most respected film editor and sound designer in modern cinema.' In a career that spans over 40 years, Murch is perhaps best known for his collaborations with Francis Ford Coppola, beginning in 1969 with The Rain People. After working with George Lucas on THX 1138 (1971), which he co-wrote, and American Graffiti (1973), Murch returned to Coppola in 1974 for The Conversation, resulting in his first Academy Award nomination. Murch's pioneering achievements were acknowledged by Coppola in his follow-up film, the 1979 Palme d'Or winner Apocalypse Now, for which Murch was granted, in what is seen as a film-history first, the screen credit 'Sound Designer.' Murch has been nominated for nine Academy Awards and has won three, for best sound on Apocalypse Now (for which he and his collaborators devised the now-standard 5.1 sound format), and achieving an unprecedented double when he won both Best Film Editing and Best Sound for his work on The English Patient. Murch’s contributions to film reconstruction include 2001's Apocalypse Now: Redux and the 1998 re-edit of Orson Welles's Touch of Evil. He is also the director and co-writer of Return to Oz (1985). In 1995, Murch published a book on film editing, In the Blink of an Eye: A Perspective on Film Editing, in which he urges editors to prioritise emotion.

Listeners: Christopher Sykes

Christopher Sykes is an independent documentary producer who has made a number of films about science and scientists for BBC TV, Channel Four, and PBS.

Tags: brain, motion, hearing, synthesis, vision

Duration: 4 minutes, 36 seconds

Date story recorded: April 2016

Date story went live: 29 March 2017