Ch 13 Motion Motion What is motion 11 08 2015 o One of the most obvious manifestations of time It is primarily the various aspects of motion that help us define the four dimensional field in media aesthetics o Perceived Motion o Film Motion and basic structural unit o Video Motion and basic structural unit o Motion frames of reference o Perceived Speed o Lens Choice and Blocking o Slow and Accelerated Motion o Synthetic Motion When something changes its position more or less continuously when compared to a stable environment we perceive motion o A car moving toward or away from us o A child running past a swing and slide on a playground o This holds true when we see the same scene on a movie or video screen although in a strict sense screen motion is illusionary The illusion of motion is created differently on film than on video Structural difference is key to explaining the enigmatic look of optical film Screen motion is illusionary Film Motion How do we create motion in a film o The Basic Structural Unit of Film Film Frame o Film photography involves taking a great number of snapshots of a moving object Each of these snapshots or frames shows the object at rest so when you hold and enlarge a film frame you cannot tell whether the object was stationary or in motion when the picture was taken Film motion is an illusion Film frame shows the object at rest regardless of whether it was in motion when it was shot Makes us see things move in our minds o Film creates the illusion of motion by taking 24 frames per seconds FPS and then playing them back at high speed Think of a little flip book in which each page shows a drawing slightly different then the previous one and when you let the pages flip rapidly the drawings seem to be in motion Why we see this position change as movement is based on the apparent motion or stroboscopic illusion Every film frame shows a unique at position in the time continuum a snapshot of part of the motion o The illusion was first created by Eadward Muybridge in Horse Photos Railroad tycoon Leeland Stanford commissioned Muybridge to take pictures of his prized racing horse Proved all 4 hooves of the horse left the ground at the same time Because of his work motion pictures were possible greatly influenced the industry 24 frames per second 24 frames per second o Camera o Projected o Persistence of Vision The theory that when we look at an image an afterimage persists in our retinas for about 1 25th of a second 1878 Video Motion This is why we do not see the black between frames The only real motion in film occurs when the projector pulls down frame after frame in front of the light source During this motion the screen is blacked out so we do not witness the pull down of each frame o Phi Phenomenon when actually seeing separate objects move Our perception of continuous movement In combination with persistence of vision this is why we see motion in film projection Structural Unit of Video and in the process of becoming and decaying an image in flux A frame that is in continuous flow o Contrary to the basic unit of film the basic structural unit of video is ALWAYS in motion The video image is created by constantly moving electron beams that scan dots on your TV set o The video screen consists of millions of pixels picture elements that are arranged in horizontal and vertical lines o When activated by a fluctuating electric charge a certain number of mosaic like dots of the video screen light up only temporarily in one of the three primary colors o The video image in NEVER complete While some of the screen dots light up others are already off again which is always in the state Contrary to the film frame of is always in a process of the being video image becoming Scanning can either be progressive or interlaced o Interlaced All of the odd lines of a frame are scanned at once then all of the even lines are scanned Our eyes see as one image Reduces flicker Uses less bandwidth o Progressive Each line is scanned one at a time from top to bottom Sharper Better motion o Motion Frames of Reference Whenever you perceive motion you automatically establish a frame of reference by which you judge the direction of the vector and its relative speed This frame of reference establishes a figure ground relationship o We have the tendency to organize a scene into figures that lie in front of a background In doing so we perceive the ground as being more stable than the figures o You normally perceive a moving object relative to its immediately more stable environment What you do in effect is establish hierarchical relationships of dependence In video and film the edges of the screen are the most basic frame of reference o For example if you see a man walking from screen right to screen left against a plain and perfectly smooth background you perceive the mans movement by where he is relative to the screen borders Within the frame the ground is made up of stable objects as compared to the less stable moving figure o For example when the background is articulated such as by a row of houses the movement of the man is judged no longer by where he is in relation to the screen edges but by where he is relative to the houses The houses are now the primary stationary reference for the man s motion Figure Ground Reversal o Sometimes the motion paradox can play tricks on you especially when you are confused about which object is doing the moving This figure ground reversal can occur when you sit in your car next to a large bus waiting for the stoplight to turn green When the bus inches forward trying to get a jump on you you may feel as though your car is rolling backward even though your foot is on the brake What is moving you or the car next to you o This principle is how car scenes were filmed for much of early cinema Dr No car chase scene made his car seem to be moving because of the car in the background getting closer and larger We can stimulate object motion on the screen by having the object figure remain stationary and the background move through a rear screen projection or a chroma key Because we know from experience that it is more likely for the car to move than the city street we perceive the street as the more stable ground against which the less stable figure the car is moving Perceived Speed Perceived Speed moving on screen It includes refers to how fast or slowly we sense something o Object Speed o The Focal Length of the Lens o Blocking how fast the object was actually
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