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Slit-scan photography

From Wikipedia, the free encyclopedia

Example of slit-scan technique (self portrait while typing on computer keyboard).  Camera is rotated into portrait orientation, and slit scan that would originally run left-to-right now runs top-to bottom
Example of slit-scan technique (self portrait while typing on computer keyboard). Camera is rotated into portrait orientation, and slit scan that would originally run left-to-right now runs top-to bottom

The slit-scan photography technique is a photographic and cinematographic process where a moveable slide, into which a slit has been cut, is inserted between the camera and the subject to be photographed.

More generally, "slit-scan photography" refers to cameras that use a slit, which is particularly used in scanning cameras in panoramic photography. This has numerous applications. This article discusses the manual artistic technique. [1]

YouTube Encyclopedic

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  • The History and Science of the Slit Scan Effect used in Stanley Kubrick's 2001: A Space Odyssey
  • How To Create Bizarre Slit Scan Video using After Effects
  • 11.7: Slit-Scan Video - p5.js Tutorial

Transcription

[Class Assembling] Welcome to Filmmaker IQ.com, I'm John Hess and today we're going to look at the largely forgotten special effect technique of Slitscan and try to recreate the Stargate Sequence from 2001: A Space Odyssey using Legos. Imagine it's 1966... this director named Stanley Kubrick comes up to you and says, "I want you to create the Stargate sequence for my new film, 2001: A Space Odysseey where Dr. David Bowman travels through time and space before landing in a cosmic zoo and ultimately being reborn as a Star Child. Yeah Buck Rogers this ain't. No film at that point treated space travel so seriously. Oh Well this shouldn't be too hard... We'll just pop open After Effects, drop in a couple pieces of artwork, throw on the 3D camera and animate it flying through this stargate tunnel. Oh wait, it's the mid sixties and the computers at the time were the size of living rooms and had less computational power than a modern calculator. Kubrick was making a serious space film and he didn't even have a full picture of Earth as seen from space - this famous one, the blue marble - the first of it's kind, was snapped by Apollo 17 Astronauts in 1972 How was this stargate effect created by the real life 2001 visual effects supervisor Douglas Trumbull? Well to find the roots of this technique we need to go back to mid 1800s and the origins of slit scan. The Pioneers of photography in the 1800s were apt to try all sorts of experimental techniques including a technique called slit scan. Slit scan is the process of putting a sliding slit between the subject and the photographic plane. The photographic medium under the slit would be exposed as the slit travelled from one side of the frame to the other. One of the earliest uses was for panorama photography. Originally developed Joseph Puchberger in Austria of 1843. the Ellipsen Daguerreotype, was a swinging lens system to capture 150 degree views onto 19-24 inch long plates - keep in mind this is the era before flexible cellulose film. The following year in 1844, Friedrich von Martens, a german living in Paris, made the Megaskop camera a similar device using a swinging lens but controlled by gears and handles. But slitscan really started to gain popularity when flexible film came into use - especially as a relatively inexpensive way of creating panoramic shots. By the turn of the century, cameras were developed with that ran the film along a curved imaging plane. The Slit would then orbit around this curved image plane creating a panorama. Slitscan had other uses as well - one really really important use was at the Race track. Gambling on races had become very popular in the 1940s and avoid the air of corruption in tight finishes, race tracks needed a photograph of who came in first. Contrary to what movies or cartoons depict, these photo finishes weren't just some guy with a flash bulb at the finish line and a hair trigger. Instead they used a variation of the slitscan called Strip photography. Strip photography uses a stationary slit and the film is moved underneath.. This photo created a record not of spatial relationships but of temporal relationships - time. The slit doesn't move - only what's in front of it. So when you look across the photo, you are looking at the exact same spot only recorded at over a period of time - the slit scan concept and it's digital derivatives continues to see use today in race tracks around the world. Slit Scan in Film So how do we get from panoramas and race track betting to a technique that can be used for motion pictures? Well in 1964 a short film titled "To the Moon and Beyond" premiered at the World's Fair in New York City. In was shot in Cinerama 360 which was a 70mm single film process using fisheye lenses and projected onto a domed screen. In attendance was Stanley Kubrick who was getting ready to shoot his grand space opus. Kubrick hired the special effects company behind "To The Moon and Beyond" to create some preliminary test shots for the 2001. One of the special effects artist working at that company, a young Douglas Trumbell, cold called Stanley Kubrick and asked to work on the film. Kubrick accepted and Trumbell spent 2 and half years working on the special effects for 2001: A Space Odyssey. For the Stargate Sequence Trumbell was inspired by the work of Animator John Whitney who also worked on "To the Moon and Beyond". John Whitney was the animator that worked with Saul Bass on the spiral graphics for Alfred Hitchcock's 1958 film Vertigo - which happens to be the first film to use a computer for animation (the computer happened to be a world war 2 artillery targeting computer). During the 1960s Whitney had been experimenting with leaving a film camera shutter open for long durations while moving artwork on motorized tables. Trumbell took Whitney's experiments and combined it with slitscan concept. His approach was to to put the slit outside of the camera. The camera was placed on a movable platform, aimed at a 4 foot slit - behind the slit were a wall of gels patterns on a moving table. When the shutter was released and the camera would dolly in toward the slit while the gels behind the slit were moved from left to right. After each 60 second exposure, the graphics on the gels would be advanced just slightly creating the animation of flying through a stargate made of light - a fitting process which bends the relationship between time and space for a scene where Doctor David Bowman is doing the same thing. This method of creating slitscan effects would continue seeing use in special effects for the next 30 years including the Dr. Who intro. Star Trek the Next Generation would also use slit scan techniques for when the Enterprise made it jump to warp speed. But once digital effects came into prominence, the painstaking slow slitscan technique fell by the wayside. Recreating the Stargate with LEGOS After looking Douglas Trumbell's schematic for his Slitscan device, I decided that making a modern day scaled down model wasn't totally out of reach - Although I may have underestimated how difficult it would be. Like most mad scientist-slash-filmmakers, I had a mechanized slider lying around. I built this a couple years ago by adding a timing belt and pulleys to a slider with the intent of being able to automate the movement. On one end of the slider, I connected the end pulley to unipole stepper motor which was controlled by a USB controller. Stepper motors are good for this application because they allow precise reproduction of movement. On the other end of the slider I attached my LEGO carriage gizmo with a large clamp. Built out of LEGO Technic gears and bricks which I had since I was a kid, this gizmo draws power from slider's timing belt, sends it through some bevel gears and a chain where it turns a worm gear. This worm gear slowly rotates a large gear on which the artwork carriage sits. The artwork itself is transparencies with various patterns printed on by an inkjet printer. In between the gizmo and the camera I placed a piece of cardboard a large slit. Using gaffer's tape I was able to get the size of the slit down to about an eighth of an inch. Creating the raw film for my stargate is really a matter of creating a timelapse with a long exposure. The stepper motor is controlled by my laptop where I can tell the motor which step to run to. I designated ZERO as my extreme close up - I gave myself a little more room so I had some space to ramp up for speed - usually setting up at step 700 - the numbers are backwards just because of how the system was set up.. From 700 I would engage the motor to head to negative 7000. Watching the motor countdown on the computer I remotely released the shutter roughly when stepper motor hit Zero. The camera would then shoot for a 20 second exposure - shooting at F22 and ISO160. The motor travels at 300 steps per second so the shutter snaps shut right around step negative 6000. The camera would continue to travel to negative 7000 - a little extra room for deceleration. - now that's one exposure done. Then it's back to 700 to set up the next exposure. Once the camera is set to go again, I advance my artwork carriage first by releasing the power chain on the gizmo and then spinning the worm gear one half turn before reattaching the powerchain. Then it's the whole process over again for the next exposure. On and on it went. At maximum efficiency I could do about 50 frames per hour - 20 seconds for the exposure, 20 seconds to reset, 10 seconds to advance the carriage and a little left over for miscellaneous activity. Although the way I describe the process seems straight forward, actually coming up with the setup was anything but. What works in theory always finds a thousand complications in application. First off, LEGOs aren't exactly the most durable building materials - the first 3 of the 5 redesigns for the gizmo were the result of dropping the it and trying to collect the pieces after they shattered across the floor. On top of that LEGO gears have some give in them which isn't great especially when working on a small level that this model is. But Legos are easy to assemble and experiment with and they were what I had available. Trying to dial in the speed of the carriage was another difficult thing to accomplish. I tried manually moving the transparency and moving the carriage itself but It wasn't until the final design which used a worm gear which I could rotate to fine tune the position did I get results that I found satisfactory. For 2001, Trumbell's slitscan machine pulled focus throughout the move and did slight pan left or right to fill the frame with the light streak - both of which I was unable to reproduce. His movement was 15 feet whereas my model only ran about 3 feet and his slit for his artwork was 4 feet high - mine was not more than 6 inches. But unlike Trumbell's machine which was fully automated, I had to babysit mine - making small adjustments for each exposure. Again and again and again... But to my advantage I have HAL, or rather After Effects. Using After Effects, I could duplicate and stretched out my image sequence, and apply nifty color effects to create my very own slitscan stargate. There's nothing quite as humbling as spending a 12 hour day creating 16 seconds of footage. As much as I have a deep appreciation of how they did it back then, I have a much deeper appreciation of just what is possible today. Slitscan has been replaced with digital processes that can accomplish much more and much more easily. The filmmakers who came before us didn't have CGI, not because they thought practicals and models or optical effects were better, but because it just wasn't available to them. But these filmmakers still strove to make the best stories they could with what they had available. Some succeeded triumphantly like Stanley Kubrick and Douglas Trumbell with 2001, but many times, as history has forgotten, some have failed. I don't think the spirit and the need to stories has changed much... Just the tools that we have available to us. The filmmakers before us created great works in spite of their technology.... So what's your excuse? Go out there, experiment, and make something great! I'm John Hess, I'll see you at Filmmaker IQ.com

Contents

Use in cinematography

Originally used in static photography to achieve blurriness or deformity, the slit-scan technique was perfected for the creation of spectacular animations. It enables the cinematographer to create a psychedelic flow of colors. Though this type of effect is now often created through computer animation, slit-scan is a mechanical technique.

John Whitney developed it for the film Vertigo for the opening credits. He sent some test sequences on film to Stanley Kubrick. The technique was adapted by Douglas Trumbull for 2001: A Space Odyssey in 1968 for the "star gate" sequence. It required a custom built machine.

This type of effect was revived in other productions, for films and television alike. For instance, slit-scan was used by Bernard Lodge to create the Doctor Who title sequences for Jon Pertwee and Tom Baker used between December 1973 and January 1980. Slit-scan was also used in Star Trek: The Next Generation (1987–1994) to create the "stretching" of the starship Enterprise-D when it engaged warp drive. Due to the expense and difficulty of this technique, the same three warp-entry shots, all created by Industrial Light and Magic for the series pilot, were reused throughout the series virtually every time the ship went into warp. Slit-scan photography was also used on Interstellar for scenes in the tesseract at the end of the movie.

Description

Slit-scan is an animation created image by image. Its principle is based upon the camera’s relative movement in relation to a light source, combined with a long exposure time. The process is as follows:

  1. An abstract colored design is painted on a transparent support
  2. This support is set down on the glass of a backlighting table and covered with an opaque masking into which one or more slits have been carved.
  3. The camera (placed high on top of a vertical ramp and decentered in relation to the light slits) takes a single photograph while moving down the ramp. The result: at the top of the ramp, when it is far away, the camera takes a rather precise picture of the light slit. This image gets progressively bigger and eventually shifts itself out of the frame. This produces a light trail, which meets up with the edge of the screen.
  4. These steps are repeated for each image, lightly peeling back the masking, which at the same time produces variation in colors as well as variation of the position of the light stream, thus creating the animation.

Naturally, this effect is very time-consuming, and thus expensive, to create. A 10-second sequence at 24 frames per second requires a minimum of 240 adjustments.

Stevemann selfportrait home-made slit-shutter camera1992.png

References

  1. ^ "The Role of the Slit-Scan Image in Science and Art". petapixel.com. 18 October 2017.

External links

This page was last edited on 12 November 2018, at 05:30
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