Three-dimensional Field: Depth and Volume
a. The Z-axis
i. Describes a point located away from the frontal plane
ii. How far an object seems to be from the camera
iii. Illusory third dimension – depth – is the most flexible dimension in film and video
iv. Originates from the screen and goes backward from the camera lens to the horizon
v. Screen width: x-axis
vi. Screen height: y-axis
vii. Screen depth: z-axis, appears to be infinite
viii. Stereovision or hologram projection : z-axis extends not only to the horizon but also to the viewer
ix. We judge the perceived distance relative to ourselves and not to the screen
b. Graphic Depth Factors
i. The farther away an object is, the smaller it appears and the higher it seems to be in the picture field
ii. Objects in the foreground are more clearly defined than those in the background
iii. Light and shadows create volume, the presence of the third dimension
iv. Five Graphic Depth Factors
1. Overlapping Planes: the most direct graphic depth view
a. The object covering the other object must be in front of it
2. Relative Size: can guess a size or know how large an object is by contextual clues, such as other object
a. Can tell how far object is by relative size of screen image
b. Larger object appears closer; Smaller object is farther
3. Height in Plane: if there are no contradictory distance clues, you will perceive objects to be more distant depending on how they are on the screen until they reach the horizon
a. Not always reliable
4. Linear Perspective: among the most powerful and convincing graphic depth factors
a. Parallel lines can merge in the distance
b. All lines converge and disappear at the vanishing point
c. Horizon Line: straight forward, parallel to ground
5. Aerial Perspective: see objects that are close to us, some more sharply than those farther away
a. This difference in foreground and background is especially pronounced in fog
i. Colors lose density and become less saturated
c. Depth Characteristics of Lenses
i. Optical characteristics of lenses can greatly enhance or hinder the illusion of a third dimension on the video or movie screen
ii. Lens choice is important in achieving the certain “feel” of a screen event
iii. Overlapping Planes
1. Wide-Angle Lens
a. Overlapping planes are reduced in prominence, but are not eliminated with the wide-angle lens
2. Narrow-Angle Lens
a. Overlapping planes are a major depth cue because the lens enlarges the background objects where things look crowded
b. Foreground and background images look similar in size
iv. Relative Size
1. Wide-Angle Lens
a. Wide-angle lens greatly exaggerates relative size
b. Objects that lie close to the camera appear relatively large, while objects on the z-axis that are only a short distance behind the close object appear dramatically smaller
2. Narrow-Angle Lens
a. Two objects seem much closer to each other because the narrow-angle lens enlarges the background
v. Linear Perspective
1. Wide-Angle Lens
a. Accelerates the convergence of parallel lines and the z-axis appears elongated
2. Narrow-Angle Lens
a. Inhibits the convergence of parallel lines and thus reduces the illusion of depth through linear perspective
b. Squeezes space and makes objects appear narrower and closer together than they actually are
vi. Aerial Perspective
1. Manipulating depth of field – the area along the z-axis that appears in focus – can achieve aerial perspective
2. Using selective focus – focusing on a specific area along the z-axis – can achieve aerial perspective
3. Wide-Angle Lens
a. Wide-angle lens generates a great depth of field, de-emphasizing aerial perspective
b. Most of the articulated z-axis appears in focus
4. Narrow-Angle Lens
a. Shallow depth of field, which emphasizes aerial perspective
b. Once focused on an object in narrow-angle lens, the areas to the foreground and background of the object become out of focus
5. Selective Focus
a. Allows you to choose the precise portion of the z-axis that you want to be in focus
6. Rack Focus
a. Involves changing the focus from one location on the z-axis to another
b. Focus on one object until another object comes into focus
c. Need a relatively shallow depth of field to achieve a rack focus, so a narrow-angle lens is used
d. 3D Stereoscopic Projection
i. Stereoscopic projection is strictly illusory and exists only in our minds and is based on a dual-lens view
ii. In stereoscopic projection, the articulated z-axis extends through the screen space toward the viewer
iii. Achieved through a dual-lens recording system, whereby the lenses are set apart similar to our eyes
1. To show the two different scenes viewed by the lenses on one screen, one is colored red and the other is cyan
2. Optical system in the viewer’s brain melds the two images into a single three-dimensional projection
iv. Different from traditional, single-lens 3D depth cues, which are contained in the visual representation of a scene from the screen back to the horizon
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