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in the movies Freeze motion is an effect which appears to have taken the motion picture world by storm. Here we take you behind the scenes to show how it is done and surprise, surprise – it is not done by computer generated effects. By BARRIE SMITH – how it’s done www.siliconchip.com.au January 2004  7 I f you’ve seen The Matrix films you’ll know the effect: the action freezes and the camera tracks around the subject, usually with Keanu Reeves, skirts akimbo and eerily aloft, while dishing it out to the evil forces. Or it may be a bullet, stopped dead, camera moving around it. If only levitation and suspension of the element of time were so easy! When viewed on the big screen, the effect is rivetting. And these days when big budget films appear to be absolutely chockers with computergenerated imagery, it’s refreshing to find this frozen-moment effect was perfected some 20 years ago by English visual artist Tim MacMillan and essentially uses well-proven photographic processes. However, the principle of capturing an event in rapid, successive frames goes farther back to the days of Eadweard Muybridge, who shot his famous horse walking/trotting/ cantering/galloping sequence (and many others) with an array of still cameras. Camera array Which brings us to the term which best describes the principle item of hardware, the ‘camera array’. Put simply, the array is a firing line of still cameras, fixed to a sturdy metal bar or truss and curved in an arc around the subject. When the subject reaches a critical point in the frame, the cameras are fired either in unison or in very close succession (typically 10 milliseconds apart). If fired simultaneously, the effect is christened ‘frozen moment’ or ‘temps mort’ (‘dead time’); if in rapid succession, the name ‘flow motion’ is employed. When the succession of frames is retrieved from the still cameras and collated together into a recognisable motion picture sequence, we get a ‘movie’. The action is frozen (the shutter speed is often as fast as 1/1000 second or more) and sharp. But when the movie is run, the camera appears to be tracking around the subject. An effective use of the effect is to edit it into a normal, 24 frame/second sequence shot; a motion picture camera is placed at either end of the still camera array and lined up to match the framing of the first or last of the multiple cameras. So the frozen moment may follow a normal speed action, precede it or even be used in the middle of the 24 frame/second sequence. Melbourne’s Mark Ruff confesses to being “obsessed with this image technique” and has spent five years or more perfecting his own system. He is the first to clarify any confusion that he is connected in any way with the team that created the marvellous effects in The Matrix films; these were achieved with a film-based system, brought to Australia by Manex. Film was also the basis of Marks’ first array, which first fired its rapid shots in 1997. The inspiration came from seeing the BBC Natural History Unit series The Human Body, which employed Tim McMillan’s Time Slice Camera: “I thought this guy is a hero for developing such a system. The Time Slice Camera holds one length of film within its casing and has a longitudinal array of lenses and shutters. Mark admits “this camera array has certain limitations”, so MacMillan invited Mark to Scotland to shoot a job: “Rather than Tim spend a lot of time and money on an array, he got me [and the gear] over to do the job and he essentially directed the time slice component.” Flare Obstacle In common with some US systems, Mark Ruff’s first approach employed 60 Pentax film SLR cameras and Sigma lenses. It worked. But there were many problems, mostly related to the build of the cameras and lens quality — flare was an obstacle — and even the shutter misfired on occasions when wear crept in. Moreover, the system was unwieldy in the post process. Not only did a cassette of 35mm film have to be loaded The principles involved in “freeze frame” photography go right back to the days of the celebrated Eadweard Muybridge (shown above right) and his amazing (for the time) “Horse in Motion” series of photographs. These were taken in 1877 as a result of an earlier wager as to whether all four of a trotting horse’s legs were ever off the ground at the same time. (He proved they were!) His work in stop-action series photography led to his invention of the “zoopraxiscope,” a primitive motion-picture machine which recreated movement by displaying individual photographs in rapid succession. 8  Silicon Chip www.siliconchip.com.au In this shot a 35mm Arriflex 435 motion picture camera is placed at the start of the still camera array and lined up to match the framing of the first of the multiple cameras and ‘hand over’ the action (moving left to right on the screen) to it. into each camera pre-shoot, the exposed films then needed processing and scanning to become a digital image file. The frames then had to be recorded onto 35mm motion picture negative and a print made. This took two days, before you could even screen the sequence! Making tests was often as costly as the final shoot. Digital to go! As many amateur snap shooters have found, going digital will not necessarily save you money. Mark Ruff figures his move to digital cost him ten times that of a film approach but he describes the difference as “chalk and cheese”. His current digital system is based on 30 Canon EOS 10D digital SLR cameras, complete with 30 Canon f3.54.5/24-85mm zoom lenses. If you walk into a camera shop, a single camera and lens will cost over $4000. A digital rig, complete with 30 cameras, lenses and firing infrastructure can be set up ready to shoot within an hour. Doing a test is virtually free — aside from time. If a problem does arise, a re-shoot can be done immediately. And as for post processing, the time from shoot to sequence preview-ready can be as short as 30 minutes. The client can then give an OK on the spot. At this point the digital to film transfer has yet to be made but these days film editing is computerised so the digital sequence can be cut into the main edit and the final recording to www.siliconchip.com.au film done when all the other material is conformed. At the moment, Mark’s ‘firing line’ can only shoot frozen moment sequences. He feels that this type of action “can be handled in more ways than a non-linear, flow motion event. A non-linear “temps mort” effect can be ping-ponged and/or zoomed into repeatedly to increase screen duration. With flow-motion the action can only go in one direction. More cameras are simply needed for flow-motion. A brace of 36 cameras is now available while 42 cameras is about the maximum the current infrastructure can handle, based mainly on the truss, which is nine metres long. With a computer algorithm called Time vs Speed The frozen moment effect simulates a motion picture camera moving at great speed. However, in the real world, it is impossible to move a film camera at these speeds. The calculations are based on a rig which is on a 9 metre long truss. Shutter speed (time is frozen) at 1/1000 second. The ‘window of time’ is one millisecond. All cameras fire in this brief moment, so it is like travelling nine metres in one millisecond; 9km/ second or 32,400 kilometres/hour. ‘sharp interpolation’, partly developed by Tim MacMillan, it is possible to create inter-frames; a 36 camera system could then produce a 72-frame sequence or even more and deliver an on-screen 3-second sequence. Normally, the cameras are spaced 20cm apart, lens centre to lens centre; this is governed by the space necessary at the camera’s side to insert and remove the CompactFlash memory card. Initially, it took Mark about a week to get the system up and running, plus a further month to reach its current form. He admits the “previous four years of R&D helped of course — as I knew exactly what to do.” What also must have helped was a degree in physics, a Bachelor of Applied Science (Photography) from RMIT and nearly a decade of real experience as a technical director for Melbourne’s Channel Ten. Mark has also owned a business/studio servicing commercial/advertising photography for almost ten years and been an ad agency staff photographer for three years. He remembers RMIT taught him “how to ‘think’ about taking a photo rather than just teaching you ‘how’ to take a photo. From camera to the Mac After a sequence is shot, all the CompactFlash cards are removed from the camera and images downloaded into a Macintosh G4 laptop: “An AppleScript sorts all the images into appropriate takes (taking about 30 seconds) and positional stabilisation achieved within minutes. Results can then be burnt to DVD as data and/or QuickTime files. It is therefore possible to shoot, do the necessary post and deliver to client all in the one day.” There are registration problems connected with so many shots taken by so many different cameras. One disadvantage of a digital camera is that the CMOS image sensor does not consistently align with the camera’s viewfinder screen: According to Mark, “It does not matter how accurate you are in an optical alignment, the pixels will never be in exactly that same spot you look at. It’s around 20-40 pixels between each camera.” But this aside, he added, it is gratifying that all images are registered so, “once a stabilisation path has been executed for that camera set up, it applies for all takes. These framing, January 2004  9 Bike Sequence: In this series of shots taken with the techniqe described in this feature, you can see how much the background changes with respect to the bike rider who appears to be moving in slow motion. The sequence runs down the columns. 10  Silicon Chip www.siliconchip.com.au scaling, and rotational errors can be minimised (eliminated) with some clever software.” Jobs done So far, Mark’s array has been used to capture frozen moment sequences in TV commercials for Toohey’s, Eveready batteries, the Nine Network plus work for an Arnott’s corporate video and various short films. Mark is also a regular visitor to India’s Bollywood, shooting TV commercials (one with cricketer Sachin Tendulkar in Mumbai) and an Indianproduced, Tasmanian-located feature, entitled ‘Boys’, which he describes as “a fantasy dream sequence … three set ups a day in different locations for seven days.” He has also “collaborated with Dayton Taylor from Time Tracks who operates another version of a multiple lens camera. We worked on a BMW shoot in Hollywood together.” What’s Next? Design is just about complete to do the following: • Control all camera settings (ISO setting, colour temperature, shutter speed, lens aperture etc) from the one CPU. This is expected to be much quicker than a number of people manually adjusting cameras. • Preview down-loading of the images could be achieved almost instantly upon exposure, by hooking into a PAL (or NTSC) video signal output from the camera. This means The EOS 10D While most digital SLR cameras have an image sensor that is half the area of the normal 35mm still film frame, by good fortune this is almost exactly the size of the motion picture frame. So data from a digital SLR has more than enough resolution for a movie, whether it be 4:3 or 16:9 or even 2.35 (CinemaScope) aspect ratio. The EOS 10D has 3072 x 2048 pixels available in its 22.7 x 15.1mm CMOS sensor. The camera also has a PAL/NTSC video output, so tapping into this for a video preview is possible. two things: on a shoot a client could see high-res results instantly. Near real time broadcast playback could also be made for various events, particularly sporting, as part of a super slow motion replay. This can be done within five seconds. Mark has already conducted a test of a video replay using a motor car race as a trial. At the moment he is bullish about the rig and its capabilities. He is confident “there are no limitations at the moment — other than the lack of an open cheque book to implement all the options possible. Even underwater is possible and an outer space project should seem easy without that gravity thing.” Contact: Mark Ruff Photography. Office 03 9887 9364. Mobile 0412 990 125. Office at F.S.A. as well – contact Russell Cunningham 02 9360 5800 Web site: www.ruffy.com Email: ruffy<at>ruffy.com Another SILICON CH Publicati IP on THE PROJECTS: High-Energy Universal Ignition System; High-Energy Multispark CDI System; Programmable Ignition Timing Module; Digital Speed Alarm & Speedometer; Digital Tachometer With LED Display; Digital Voltmeter (12V or 24V); Blocked Filter Alarm; Simple Mixture Display For Fuel-Injected Cars; Motorbike Alarm; Headlight Reminder; Engine Immobiliser Mk.2; Engine Rev Limiter; 4-Channel UHF Remote Control; LED Lighting For Cars; The Booze Mail order prices: Aust: $14.95 (incl. GST & P&P) Buster Breath Tester; Little Dynamite Subwoofer; Neon NZ/Asia Pacific: $18.00 via airmail Tube Modulator. Rest of World: $21.50 via airmail Order direct from the publishers (don’t forget your address info and credit card details): PHONE: FAX: EMAIL: (02) 9979 5644 (02) 9979 6503 Details to 9pm-5pm 24 hours a day office<at>siliconchip.com.au Mon-Friday www.siliconchip.com.au WEB: Via siliconchip.com.au (click on order form) MAIL: Silicon Chip Publications PO Box 139 Collaroy NSW 2097 January 2004  11