The New Language of Stereoscopic Filmmaking

The stereoscopic medium is moving from a challenge focused around aligning dual cameras into one based on artistic choices. Already terms like ”convergence,”“interocular,” and “screen plane” are forming part of the burgeoning new visual grammar, which might soon become as natural to filmmaking vocabulary as ”close-up” or “racking focus.”

Photo by austinevan

While the industry continues to build 3D expertise, some technical jargon is unavoidable. Perhaps the most fundamental idea to grasp is that to match human stereo vision, two cameras need placing with their optical centers roughly 2.5 inches apart—the same interocular as human eyes.

“Much like the way that color and contrast in a film image is exaggerated to enhance the theatrical experience, the interocular distance, or more correctly, interaxial separation, is often increased to exaggerate the stereo effect, and add impact to the viewed image,” explains digital film consultant Steve Shaw. “The problem though, is that it is not that simple in practice, as the impact of the stereoscopic image can be affected by more than the simple quantity of the stereo effect.”

Since the main conceptual difference between 2D and 3D involves the addition of depth or space this requires some essential new terminology. For example, whereas in 2D filmmakers work only in terms of width and height, otherwise known as the x- and y-axis, working in 3D means they can also work with depth—or along the z-axis, which is also known as “z” space. Good composition and blocking of talent, props, or sets within “z” space is crucial to making the most of 3D.

The amount of 3D that emerges out-of-screen is known as “negative parallax”; the amount of 3D on-screen as “zero parallax” or the point at which the images converge; and the amount of 3D that appears into-the-screen is termed “positive parallax.” Many filmmakers work with a depth budget, which is described as a percentage of parallax between near and far objects, behind or in front of the screen, and keeps the 3D within parameters that make for comfortable viewing.

According to stereographer Alain Derobe ( PINA ), “Audiences always want to be as close as possible to the action, but as soon as something comes out of the screen, to invade the auditorium, spectators withdraw in their seats, and they all become conscious that they’re just ‘watchers,’ and realize that the element invading their space is nothing but a picture.”

A new stereo language could get incredibly technical, wrapped up in calculus for measuring interaxial distances against focal length, determining the precise matching of lenses as they rotate and move through a zoom, or analyzing disparity values for every pixel.

However, many of the filmmakers we feature freely admit that they prefer to use more descriptive terms. Instead, to convey the effect that they want to achieve with 3D they use more descriptive terms such as “dial up” (or “dial down”) the stereo, “punchy” (or shallow”), “volume,” “natural depth,” “immersive,” and “roundness,” or simply “give me more (or less)” 3D.

A depth script, for example, is analogous to a musical score. It outlines the amount of 3D (the depth budget) at particular points in a script to underscore mood and emotion and to help tell the story. Broadly speaking, once you understand the emotion you want to achieve from the shot, you can think about how to use 3D to evoke it.

“Filmmakers are adopting a new language to describe how they want the 3D to work for a particular scene. But it is not an exact science and there is no creative industry bible you can refer to,” says Jamie Beard, who worked with Steven Spielberg on The Adventures of Tintin. “Consequently, descriptions can be a little broad, often using a very emotional type of language, but nonetheless one that is understood in context. “After all, people’s interpretation of conventional film grammar can vary,” he adds. “A two-shot for one person might mean framing from the hips, to another it can mean framing from the feet. In the context of the scene it is understood. “So when talking about convergence on Tintin everyone understood what is meant by ‘throw it back’ or ‘pull it closer’ or when asking for the stereo to be ‘more punchy,’ or simply ‘more stereo.’ It doesn’t need to get much more technical than that.”

Making Hugo, Scorsese says, “I didn’t use any technical language but rather my own emotional and intellectual response to the image. If I wanted to [push the 3D] further I would communicate that, or if there was something troubling me, I’d hold back. I would demand more or less IO [interocular distance]—I learned that. For me it was a question of how much more we could chisel away at the sculpture.”

Excerpt from Exploring 3D: The New Grammar of Stereoscopic Filmmaking by Adrian Pennington, Carolyn Giardina © 2012 Taylor & Francis Group. All Rights Reserved.

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