Shannon Benna Systems and Practices to Produce Stereoscopic Space on Screen When we as filmmakers, photographers and artists try to to the viewer. I think this is more often the way stereoscopic create an image, we are bound by the technical constraints 3D has been used, however, I don’t think it is always because of the machines or mediums we use. Through increasing- it was the intent of the creator, but due to the way the con- ly complex mechanisms or processes, we have been able to tent is delivered to the viewer. For example, if you create a reproduce the images we perceive with our eyes more and 3D image that is true-to-life in depth and scale, accurately more realistically. We have also been able to manipulate recreating the way the average person would view another images to express an imagined aesthetic, intended to con- person, or an orthostereo image, you must also present it to vey an artistic vision, an emotion, or a forced perception the viewer in such a way that they are viewing the image designed to inspire sympathy/empathy for an unusual per- from the same position that the camera was capturing it, spective. Whether we are discussing black and white, color, and without their being aware the image is being projected. still, moving, realistic, fantastical, 2D, or stereoscopic 3D Then the viewer would be unaware they were experienc- images, we must not only consider how the image is tech- ing an optical illusion. Whereas, if an orthoscopic image nically created, but also how it is delivered to the viewer. is projected onto a screen in a theater, the viewer experi- An image viewed on a small, personal screen (like a tablet ences the image as part of an audience, as opposed to as an or cell phone) will create a different relationship with the one-on-one experience, and the image is now larger than viewer than the same image viewed on a theatrical screen. life in scale, rendering it no longer realistic, but fantastical. Likewise, a shared viewing experience in public will cre- With the advent of modern immersive media we are given ate a different response than one experienced via a virtual the opportunity to place viewers inside of the world of our reality (VR) headset. choosing in a whole new way. Although VR can give us a As a filmmaker who has worked in both 2D and 3D complete sphere to visit, only with stereoscopic imaging can media, I find that although 3D imaging provides an avenue the environment become truly immersive in the sense of to recreating the most realistic version of the world that we granting the individual a real-life perception opportunity. see every day, it is not always presented in a way that gives Via this presentation method we can engage a viewer in an the viewer a real-to-life experience. Additionally, stereo- orthoscopic version of an alternate reality, whether it is real- scopic 3D can provide a way for an artist to create a fantas- ism or fantastical, allowing for a whole new way for artists tical world-view and present an alternate version of reality to connect with their audience. Shannon Benna Therefore, to utilize stereoscopic imaging to its fullest Rules for Creating and Manipulating Stereo- capability, we must understand its technical constraints and scopic Space requirements and we must make a conscious decision about the intended purpose of the images from the beginning. We To begin, one should understand the basic premise behind must not only go through a procedure that ensures the imag- stereoscopic imaging. It requires two images, a left and es we create will be viewable as 3D images, and not cause right, representative of and ultimately delivered to each of pain or nausea to our viewer, but also choose the right set of the viewer’s eyes, discretely. As we all see in three dimen- tools to capture and deliver our images, accurately express- sions everyday (unless we are part of the 6–12% of the pop- 1 Parallax, R/C (all images marked R/C can be viewed stereoscopically ing our intentions towards reality or fantasy and immersion ulation that suffers stereo blindness, or an inability to see in with red/cyan anaglyph glasses). vs. presentation. Then, once we have chosen our toolset, the depth) we are pre-equipped with the firmware in our brains subtle adjustments we make to the settings of our tools will to take in these two separate right and left eye images and convey the emotional and physical sensations we intend, as fuse them into an all-encompassing perception of space, well as the perspective we present, including the immersive, complete with volumetric objects living at some distance intimate, spectator and/or voyeuristic quality of the images. from us physically. This process is called stereopsis, and As both a practitioner and an educator of stereoscop- those who can perceive depth possess binocular vision. ic 3D imaging and media production, I believe the key to The amount of separation between the eyes is known this and any discipline is communication. Herein lies a bit as inter-ocular (IO) separation, while the distance between of a problem, as our terminology is not truly standardized. the imaging sensors is known as the inter-axial (IA) distance. There are multiple ways to refer to the same effect, error, These terms are often used interchangeably and are mea- process, or action, which are not only diversified between sured in a variety of different units: inches, centimeters, production teams or academic institutions, but also between percentage of screen size, and pixels. Although it may seem stages of production. The way one speaks of 3D in pre-visu- extreme, we are concerned with pixel accurate measure- alization, development and appreciation is often different ments, as this can mean the difference between an image than the terminology used in production, or in post-produc- that is comfortable to view, and too deep for the average per- tion. There isn’t even consistency between editorial, finish- son to fuse. Through stereoscopic imaging we are able to ing, and conversion, which are all post-production practices. trompe l’œil or fool the eye into believing these two images, To aid us in this publication, any terms will be typeset in a captured from two slightly different perspectives are actual- visually different manner for ease of recognition. There is a ly a three dimensional object, landscape or world. The wider glossary of terms and accompanying illustrations to facili- the separation between the same object in each of the imag- tate comprehension as well. es when overlaid, or parallax (fig. 1), determines the amount of depth in the image. Too much parallax can render the image unresolvable, as the eyes would be forced to diverge or strain towards the periphery in order to attempt to fuse 134 the stereo pair into a single image. Systems and Practices to Produce Stereoscopic Space on Screen 2 Z-Space. 3 Edge violation above, correct 4 Floating window 5 Convergence in stereo-space. framing below, R/C. correction. Along with being able to control the amount of depth We can angle the screen plane to accommodate this cre- in a stereoscopic image, we are also able to choose where ative choice by employing a floating window (fig. 4), or a black 6 Parallax seperation in 3D image, objects are placed in relation to the screen plane, or where mask that is applied to the side of one eye to bevel that side R/C. they are placed along the Z axis (fig. 2). Objects behind the of the screen plane backwards in space. This technique is screen plane are in positive Z space, while objects that are used exclusively in a traditional presentation method, in VR in front of the screen, or float into the audience’s space are there is no off-screen, and thus no stereo window to consider. in negative Z space. It is often difficult to perceive the actual Objects that appear at the screen plane are at zero par- screen plane, and in some cases, especially VR presentation, allax and are considered to be the point of convergence. The the screen plane does not truly exist. We do use the con- point of convergence is the point at which our eyes cross cept of the screen plane to describe zero parallax, for ease when we naturally observe the world (fig. 5), or where the of discussion, especially while creating images and using two imaging devices’ lines of sight cross when capturing traditional on-set monitors. images. If we choose to set convergence during the initial If an object is intended to be positioned in negative Z imaging stage, we are said to be shooting converged and space, it must not be clipped off in any unnatural fashion but we set a degree of rotation that the cameras will turn in be imaged as a whole. If part of the object exists off screen towards each other for each shot to decide where objects/ it must also be in positive Z space. If the object/subject is subjects will be positioned along the Z axis (fig. 6). both partially off screen and in negative Z space, the effect It is not necessary to converge the lines of sight when is called an edge violation (fig. 3) and causes confusion in the initially imaging. If we do not, it will give the effect that all brain. A person or thing cannot be simultaneously outside of of the image appears in negative Z space and is referred to as a window and inside at the same time without being angled.