American Cinematographer - April 2008 - (Page 56)

were to remove your glasses, you would see both images simultaneously, as in the Fig. 6 example of a behind-screen object viewed without special glasses. Next, we want an object to appear in front of the screen plane so that from the audience’s perspective, the object appears to be coming into the theater and closer to the viewer’s face. This is achieved on set by adjusting the convergence of the leftand right-camera lenses so they are converging in front of the in-theater screen plane. When projected, the images are viewed by the audience as illustrated in Fig. 7. This technique can be used to make audience members perceive that an object is very, very close to their faces. This creates a very effective 3-D illusion, but experience has shown that extreme examples of this effect should be used sparingly, if at all. Remember that while the viewer will be converging that object mere inches from his face, he will still be focusing on the screen plane many feet away. As a result, this type of 3-D “gag,” when properly done, always gets gasps from an audience, yet, because of that disparity of focus, never quite matches our reality. This example illustrates an 56 April 2008 important difference between 3-D movies and what you experience in real life. In life, when an object is half a foot from your face, your eyes converge and focus at half a foot from your face. In a 3-D movie environment, you can choose an angle of view and scale that, from your perspective, makes an object appear to be half a foot from your face even as your eyes are focused on the screen plane, which may be anywhere from 15' to 100' away from you. This doesn’t mean the 3-D approach is “wrong”; it’s just an example of why 3-D depth cues in a 3-D movie often seem to be exaggerated — why 3-D movies seem to be more 3-D than reality. When an object appears on the screen plane, every member of the audience sees the object at the same location on the screen because the left- and right-eye images appear precisely laid on top of each other (and thus appear as one image). Basically, the image appears the same as it would during a regular 2-D movie projection (Fig. 8). Take a look at Fig. 9, however, and see how things change when an object is placed behind the screen plane. As you can see, a person’s specific location in the theater will affect his perception of where that behindscreen object is located. Also, how close that person is to the screen will affect how far behind the screen that object appears to be; the closer one’s seat is to the screen, the shorter the distance between the screen and the object “behind” it appears to be. Again, it is not “wrong” that this happens. Fig. 9 simply clarifies the point that stereoscopic cinematography is not 3-D. Were it truly 3-D, every audience member would see these behind-screen objects in the same location. When planning shots for a 3-D motion picture, the filmmaker should be conscious of how a dramatic moment might be received by viewers seated in various locations. My next points concern the proscenium arch and “offscreen” objects. As mentioned earlier, the edges of the screen image (top, bottom, left and right) are collectively referred to as the proscenium arch. This is a nod towards live theater, where the term applies to that area of the stage in front of the curtain. In 3-D, the term is used when referring to objects that appear to be in front of the screen plane. In short, the edges of the screen are relevant to objects appearing in front of the screen plane. Such an object can have very strong stereoscopic convergence cues that will make it appear to be “floating” very close to a viewer’s face. A good example of this phenomenon occurs in the film Muppet*Vision 3D, during a scene in which the characters Waldo and Kermit the Frog appear to extend into the audience while clinging to the end of a ladder. A more recent example of this principle can be seen in Beowulf, when a spear is thrust toward Beowulf ’s face after he arrives on a beach. If that floating object moves so close to the edge of the screen that it is occluded by that edge, your brain will quickly employ its knowl-

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American Cinematographer - April 2008 Contents Editor's Note Global Village: The Counterfeiters Short Takes: Milia Production Slate: Paranoid Park Production Slate: All the Boys Love Mandy Lane Card Sharks Temple of Doom 3-D Cinematography Sundance 2008: Mining for Movies Post Focus: Digital Film Tree Gets into Peyote Post Focus: FotoKem’s 3-D Workflow Post Focus: Technicolor Digs in at Pinewood Filmmakers’ Forum: Steven Fierberg, ASC on Searchers 2.0 New Products & Services International Marketplace Classified Ads Ad Index Clubhouse News ASC Close-Up: Rodney Taylor

American Cinematographer - April 2008

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