DOCSLIB.ORG

THE INFLUENCES of STEREOSCOPY on VISUAL ARTS Its History, Technique and Presence in the Artistic World

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
THE INFLUENCES of STEREOSCOPY on VISUAL ARTS Its History, Technique and Presence in the Artistic World University of Art and Design Cluj-Napoca PhD THESIS SUMMARY THE INFLUENCES OF STEREOSCOPY ON VISUAL ARTS Its history, technique and presence in the artistic world PhD Student: Scientific coordinator: Nyiri Dalma Dorottya Prof. Univ. Dr. Ioan Sbârciu Cluj-Napoca 2019 1 CONTENTS General introduction ........................................................................................................................3 Chapter 1: HISTORY OF STEREOSCOPY ..............................................................................4 1.1 The theories of Euclid and the experiments of Baptista Porta .........................................5 1.2 Leonardo da Vinci and Francois Aguillon (Aguilonius) .................................................8 1.3 The Inventions of Sir Charles Wheatstone and Elliot ...................................................18 1.4 Sir David Brewster's contributions to the perfection of the stereoscope .......................21 1.5 Oliver Wendell Holmes, the poet of stereoscopy ..........................................................23 1.6 Apex of stereoscopy .......................................................................................................26 1.7 Underwood & Keystone .................................................................................................29 1.8 Favorite topics in stereoscopy ........................................................................................32 1.8.1 Genre Scenes33 .........................................................................................................33 1.8.2 Landscapes ................................................................................................................33 1.8.3 Tragedies ...................................................................................................................34 1.8.4 Adolph Block - Wizards ...........................................................................................36 1.9 Recent research in stereoscopy .......................................................................................37 Chapter 2: STEREOSCOPY TECHNIQUE ..............................................................................40 2.1 Causes of stereoscopic vision ........................................................................................42 2.2 Objective space ..............................................................................................................52 2.3 The Monocular View .....................................................................................................56 2.4 Binocular vision ............................................................................................................59 2.5 Rivalry ...........................................................................................................................61 2.6 Convergence ..................................................................................................................61 2.7 Differentiation ...............................................................................................................63 2.8 Benefits of Binocular Vision .........................................................................................66 2.9 Photographic principles in stereoscopy .........................................................................70 2 Chapter 3: THE INFLUENCES OF STEREOSCOPY ON THE ARTISTIC WORLD .......77 3.1 Leonardo - The first pair of stereoscopic paintings .......................................................79 3.2 Paul Cézanne - The painter and the mountain ...............................................................94 3.3 Marcel Duchamp - Rethinking Stereoscopy ................................................................104 General conclusions ...................................................................................................................113 Index ............................................................................................................................................116 Bibliography ...............................................................................................................................118 Summary .....................................................................................................................................121 3 Keywords: Stereoscopy, Photography, Depth, Illusion, Optics, Physics, Art, Three-dimensionality, Two- dimensionality, Binoculars, Science, Lenses In my PhD work I try to analyse the actuality of stereoscopy and the continuing fascination it represents in the artistic world. To what extent can we talk about a constant of illusionism in the history of visualization? What are the continuity elements and what has the technology brought to the non-mechanized stereoscopy? How does stereoscopy work and what are the challenges it addresses to our senses? What is the contribution of artists in the development and diversification of perceptual experiences based on stereoscopy? In this research, I will try to answer these questions by analysing the history, technique, science and artistic aspect of stereoscopy, a less known side in the artistic environment. Stereoscopy through its "magical" offer, has attracted long-standing glances. But not only the average man was impressed, but also renowned artists, who persevered in their pursuit of techniques as diverse and refined as possible to render an image so that the feeling of spatiality is as intense as possible. Stereoscopy is a branch of optics that deals with the processes of recording and rendering images in relief and depth by examining the optical-mechanical properties of the instruments used for this purpose. The term derives from the Greek words: stereos = solid and scopein = to search, to examine. The stereoscope is based on the principle of human visual perception, whereby both eyes transmit a slightly different image to the brain, according to their position. These two images are combined in the brain and through this fusion one can perceive a single spatial image "in relief". The human brain approximates the differences between the two images with the help of the parallax effect, thus giving the illusion of a three-dimensional image. The more shots you have, the more impressive the three-dimensional image will result. If we look at stereograms, the sensation is as if we were looking at a landscape through a window. The colour, size, space, depth and distance are as perceptible as the original space. Stereoscopic presentation is an optical system whose finalizer is the human brain. The binocular vision as a phenomenon was mentioned in antiquity by Euclid and Galen, then Leonardo da Vinci deepened this topic in 1484 in the Milan manuscript. He faced the notion of perception of the world through 2 different images that correspond to the gaze. The purpose was to play different images for each eye, through a technical device. Also stereoscopy was approached by the Italian philosopher Della Porta in 1594 and by Francois Aguillon (Aguilonius) in 1613. One such device, called a stereoscope, was designed by English physicist Charles Wheatstone. On June 21, 1838 he gave lectures on his discoveries on stereoscopic phenomena in the Royal Society of London and in the report "physiology of vision" presented an optical instrument, called "stereoscope". His findings were argued with drawings and gave birth to the first stereoscopic viewer that worked with the help of mirrors. As a result of misperforming basic information, a number of problems have arisen, such as stereograms that cause headaches or dizziness. In 1839, the Frenchman Daguerre discovered the method of rendering permanent photographic images by taking pictures with the camera obscura. Thus, it was possible not only to draw stereograms, but also to photograph them. In 1844 the English physicist, Sir David Brewster, the inventor of the kaleidoscope put this idea into practice, namely that the photograph be applied in stereoscopy. He tried in vain to arouse the interest of opticians in London and Birmingham for his first models. In 1849 he improved the stereoscope, thus making the first authentic 2-lens stereo camera. The most popular topics of stereographers were genre scenes, landscapes, natural disasters and nudes. With the progress of photo reproduction through print, the Holmes manual stereoscope, invented by Oliver Wendell Holmes, appeared in 1859. It is interesting to note that Wheatstone, Brewster and Holmes did not patent their inventions. The reputation of this type of camera has allowed the popularity of this technology to increase among photography enthusiasts. The high-performance technology of this invention has produced important changes in the conception of photography. It affected the vision of the photographer, but also of the public regarding their perception of relief and depth. It influenced the whole way of reading the images and evaluating the content. Until recently, the binocular separable sensation of depth was not realized. Over the years, people like Euclid and Leonardo have come to understand that our eyes see different images of the world around us. But Sir Charles Wheatstone, with his stereoscope and drawings, was the first person to demonstrate that it was a unique sense of depth, stereopsis, produced by retinal differentiation. Euclid, Kepler and many others have asked why we don't see a double picture about the visual world. Wheatstone solved the problem by demonstrating the brain's fusion of two retinal
Load more

Recommended publications
  • Stereoscopic Vision, Stereoscope, Selection of Stereo Pair and Its Orientation
    International Journal of Science and Research (IJSR) ISSN (Online): 2319-7064 Impact Factor (2012): 3.358 Stereoscopic Vision, Stereoscope, Selection of Stereo Pair and Its Orientation Sunita Devi Research Associate, Haryana Space Application Centre (HARSAC), Department of Science & Technology, Government of Haryana, CCS HAU Campus, Hisar – 125 004, India , Abstract: Stereoscope is to deflect normally converging lines of sight, so that each eye views a different image. For deriving maximum benefit from photographs they are normally studied stereoscopically. Instruments in use today for three dimensional studies of aerial photographs. If instead of looking at the original scene, we observe photos of that scene taken from two different viewpoints, we can under suitable conditions, obtain a three dimensional impression from the two dimensional photos. This impression may be very similar to the impression given by the original scene, but in practice this is rarely so. A pair of photograph taken from two cameras station but covering some common area constitutes and stereoscopic pair which when viewed in a certain manner gives an impression as if a three dimensional model of the common area is being seen. Keywords: Remote Sensing (RS), Aerial Photograph, Pocket or Lens Stereoscope, Mirror Stereoscope. Stereopair, Stere. pair’s orientation 1. Introduction characteristics. Two eyes must see two images, which are only slightly different in angle of view, orientation, colour, A stereoscope is a device for viewing a stereoscopic pair of brightness, shape and size. (Figure: 1) Human eyes, fixed on separate images, depicting left-eye and right-eye views of same object provide two points of observation which are the same scene, as a single three-dimensional image.
    [Show full text]
  • Interacting with Autostereograms
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/336204498 Interacting with Autostereograms Conference Paper · October 2019 DOI: 10.1145/3338286.3340141 CITATIONS READS 0 39 5 authors, including: William Delamare Pourang Irani Kochi University of Technology University of Manitoba 14 PUBLICATIONS 55 CITATIONS 184 PUBLICATIONS 2,641 CITATIONS SEE PROFILE SEE PROFILE Xiangshi Ren Kochi University of Technology 182 PUBLICATIONS 1,280 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Color Perception in Augmented Reality HMDs View project Collaboration Meets Interactive Spaces: A Springer Book View project All content following this page was uploaded by William Delamare on 21 October 2019. The user has requested enhancement of the downloaded file. Interacting with Autostereograms William Delamare∗ Junhyeok Kim Kochi University of Technology University of Waterloo Kochi, Japan Ontario, Canada University of Manitoba University of Manitoba Winnipeg, Canada Winnipeg, Canada [email protected] [email protected] Daichi Harada Pourang Irani Xiangshi Ren Kochi University of Technology University of Manitoba Kochi University of Technology Kochi, Japan Winnipeg, Canada Kochi, Japan [email protected] [email protected] [email protected] Figure 1: Illustrative examples using autostereograms. a) Password input. b) Wearable e-mail notification. c) Private space in collaborative conditions. d) 3D video game. e) Bar gamified special menu. Black elements represent the hidden 3D scene content. ABSTRACT practice. This learning effect transfers across display devices Autostereograms are 2D images that can reveal 3D content (smartphone to desktop screen). when viewed with a specific eye convergence, without using CCS CONCEPTS extra-apparatus.
    [Show full text]
  • Multi-Perspective Stereoscopy from Light Fields
    Multi-Perspective stereoscopy from light fields The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Changil Kim, Alexander Hornung, Simon Heinzle, Wojciech Matusik, and Markus Gross. 2011. Multi-perspective stereoscopy from light fields. ACM Trans. Graph. 30, 6, Article 190 (December 2011), 10 pages. As Published http://dx.doi.org/10.1145/2070781.2024224 Publisher Association for Computing Machinery (ACM) Version Author's final manuscript Citable link http://hdl.handle.net/1721.1/73503 Terms of Use Creative Commons Attribution-Noncommercial-Share Alike 3.0 Detailed Terms http://creativecommons.org/licenses/by-nc-sa/3.0/ Multi-Perspective Stereoscopy from Light Fields Changil Kim1,2 Alexander Hornung2 Simon Heinzle2 Wojciech Matusik2,3 Markus Gross1,2 1ETH Zurich 2Disney Research Zurich 3MIT CSAIL v u s c Disney Enterprises, Inc. Input Images 3D Light Field Multi-perspective Cuts Stereoscopic Output Figure 1: We propose a framework for flexible stereoscopic disparity manipulation and content post-production. Our method computes multi-perspective stereoscopic output images from a 3D light field that satisfy arbitrary prescribed disparity constraints. We achieve this by computing piecewise continuous cuts (shown in red) through the light field that enable per-pixel disparity control. In this particular example we employed gradient domain processing to emphasize the depth of the airplane while suppressing disparities in the rest of the scene. Abstract tions of autostereoscopic and multi-view autostereoscopic displays even glasses-free solutions become available to the consumer. This paper addresses stereoscopic view generation from a light field. We present a framework that allows for the generation However, the task of creating convincing yet perceptually pleasing of stereoscopic image pairs with per-pixel control over disparity, stereoscopic content remains difficult.
    [Show full text]
  • STAR 1200 & 1200XL User Guide
    STAR 1200 & 1200XL Augmented Reality Systems User Guide VUZIX CORPORATION VUZIX CORPORATION STAR 1200 & 1200XL – User Guide © 2012 Vuzix Corporation 2166 Brighton Henrietta Town Line Road Rochester, New York 14623 Phone: 585.359.5900 ! Fax: 585.359.4172 www.vuzix.com 2 1. STAR 1200 & 1200XL OVERVIEW ................................... 7! System Requirements & Compatibility .................................. 7! 2. INSTALLATION & SETUP .................................................. 14! Step 1: Accessory Installation .................................... 14! Step 2: Hardware Connections .................................. 15! Step 3: Adjustment ..................................................... 19! Step 4: Software Installation ...................................... 21! Step 5: Tracker Calibration ........................................ 24! 3. CONTROL BUTTON & ON SCREEN DISPLAY ..................... 27! VGA Controller .................................................................... 27! PowerPak+ Controller ......................................................... 29! OSD Display Options ........................................................... 30! 4. STAR HARDWARE ......................................................... 34! STAR Display ...................................................................... 34! Nose Bridge ......................................................................... 36! Focus Adjustment ................................................................ 37! Eye Separation ...................................................................
    [Show full text]
  • A Novel Walk-Through 3D Display
    A Novel Walk-through 3D Display Stephen DiVerdia, Ismo Rakkolainena & b, Tobias Höllerera, Alex Olwala & c a University of California at Santa Barbara, Santa Barbara, CA 93106, USA b FogScreen Inc., Tekniikantie 12, 02150 Espoo, Finland c Kungliga Tekniska Högskolan, 100 44 Stockholm, Sweden ABSTRACT We present a novel walk-through 3D display based on the patented FogScreen, an “immaterial” indoor 2D projection screen, which enables high-quality projected images in free space. We extend the basic 2D FogScreen setup in three ma- jor ways. First, we use head tracking to provide correct perspective rendering for a single user. Second, we add support for multiple types of stereoscopic imagery. Third, we present the front and back views of the graphics content on the two sides of the FogScreen, so that the viewer can cross the screen to see the content from the back. The result is a wall- sized, immaterial display that creates an engaging 3D visual. Keywords: Fog screen, display technology, walk-through, two-sided, 3D, stereoscopic, volumetric, tracking 1. INTRODUCTION Stereoscopic images have captivated a wide scientific, media and public interest for well over 100 years. The principle of stereoscopic images was invented by Wheatstone in 1838 [1]. The general public has been excited about 3D imagery since the 19th century – 3D movies and View-Master images in the 1950's, holograms in the 1960's, and 3D computer graphics and virtual reality today. Science fiction movies and books have also featured many 3D displays, including the popular Star Wars and Star Trek series. In addition to entertainment opportunities, 3D displays also have numerous ap- plications in scientific visualization, medical imaging, and telepresence.
    [Show full text]
  • Investigating Intermittent Stereoscopy: Its Effects on Perception and Visual Fatigue
    ©2016 Society for Imaging Science and Technology DOI: 10.2352/ISSN.2470-1173.2016.5.SDA-041 INVESTIGATING INTERMITTENT STEREOSCOPY: ITS EFFECTS ON PERCEPTION AND VISUAL FATIGUE Ari A. Bouaniche, Laure Leroy; Laboratoire Paragraphe, Université Paris 8; Saint-Denis; France Abstract distance in virtual environments does not clearly indicate that the In a context in which virtual reality making use of S3D is use of binocular disparity yields a better performance, and a ubiquitous in certain industries, as well as the substantial amount cursory look at the literature concerning the viewing of of literature about the visual fatigue S3D causes, we wondered stereoscopic 3D (henceforth abbreviated S3D) content leaves little whether the presentation of intermittent S3D stimuli would lead to doubt as to some negative consequences on the visual system, at improved depth perception (over monoscopic) while reducing least for a certain part of the population. subjects’ visual asthenopia. In a between-subjects design, 60 While we do not question the utility of S3D and its use in individuals under 40 years old were tested in four different immersive environments in this paper, we aim to position conditions, with head-tracking enabled: two intermittent S3D ourselves from the point of view of user safety: if, for example, the conditions (Stereo @ beginning, Stereo @ end) and two control use of S3D is a given in a company setting, can an implementation conditions (Mono, Stereo). Several optometric variables were of intermittent horizontal disparities aid in depth perception (and measured pre- and post-experiment, and a subjective questionnaire therefore in task completion) while impacting the visual system assessing discomfort was administered.
    [Show full text]
  • 2018 First Call for Papers4 2013+First+Call+For+Papers+V4.Qxd
    FIRST CALL FOR PAPERS Display Week 2018 Society for Information Display INTERNATIONAL SYMPOSIUM, SEMINAR & EXHIBITION May 20 – 25, 2018 LOS ANGELES CONVENTION CENTER LOS ANGELES, CALIFORNIA, USA www.displayweek.org • Photoluminescence and Applications – Using quantum Special Topics for 2018 nanomaterials for color-conversion applications in display components and in pixel-integrated configurations. Optimizing performance and stability for integration on- The Display Week 2018 Technical Symposium will chip (inside LED package) and in remote phosphor be placing special emphasis on four Special Topics configurations for backlight units. of Interest to address the rapid growth of the field of • Micro Inorganic LEDs and Applications – Emerging information display in the following areas: Augmented technologies based on scaling down inorganic LEDs for Reality, Virtual Reality, and Artificial Intelligence; use as arrayed emitters in display applications, with Quantum Dots and Micro-LEDs; and Wearable opportunities from large video displays down to high Displays, Sensors, and Devices. Submissions relating resolution microdisplays. Science and technology of to these special topics are highly encouraged. micro LED devices, materials, and processes for the fabrication and integration with electronic drive back- 1. AUGMENTED REALITY, VIRTUAL REALITY, AND planes. Color generation, performance, and stability. ARTIFICIAL INTELLIGENCE (AR, VR, AND AI) Packaging and module assembly solutions for emerging This special topic will cover the technologies and
    [Show full text]
  • Construction of Autostereograms Taking Into Account Object Colors and Its Applications for Steganography
    Construction of Autostereograms Taking into Account Object Colors and its Applications for Steganography Yusuke Tsuda Yonghao Yue Tomoyuki Nishita The University of Tokyo ftsuday,yonghao,[email protected] Abstract Information on appearances of three-dimensional ob- jects are transmitted via the Internet, and displaying objects q plays an important role in a lot of areas such as movies and video games. An autostereogram is one of the ways to represent three- dimensional objects taking advantage of binocular paral- (a) SS-relation (b) OS-relation lax, by which depths of objects are perceived. In previous Figure 1. Relations on an autostereogram. methods, the colors of objects were ignored when construct- E and E indicate left and right eyes, re- ing autostereogram images. In this paper, we propose a L R spectively. (a): A pair of points on the screen method to construct autostereogram images taking into ac- and a single point on the object correspond count color variation of objects, such as shading. with each other. (b): A pair of points on the We also propose a technique to embed color informa- object and a single point on the screen cor- tion in autostereogram images. Using our technique, au- respond with each other. tostereogram images shown on a display change, and view- ers can enjoy perceiving three-dimensional object and its colors in two stages. Color information is embedded in we propose an approach to take into account color variation a monochrome autostereogram image, and colors appear of objects, such as shading. Our approach assign slightly when the correct color table is used.
    [Show full text]
  • The Varriertm Autostereoscopic Virtual Reality Display
    submission id papers_0427 The VarrierTM Autostereoscopic Virtual Reality Display Daniel J. Sandin, Todd Margolis, Jinghua Ge, Javier Girado, Tom Peterka, Thomas A. DeFanti Electronic Visualization Laboratory University of Illinois at Chicago [email protected] Abstract In most other lenticular and barrier strip implementations, stereo is achieved by sorting image slices in integer (image) coordinates. Virtual reality (VR) has long been hampered by the gear Moreover, many autostereo systems compress scene depth in the z needed to make the experience possible; specifically, stereo direction to improve image quality but Varrier is orthoscopic, glasses and tracking devices. Autostereoscopic display devices are which means that all 3 dimensions are displayed in the same gaining popularity by freeing the user from stereo glasses, scale. Besides head-tracked perspective interaction, the user can however few qualify as VR displays. The Electronic Visualization further interact with VR applications through hand-held devices Laboratory (EVL) at the University of Illinois at Chicago (UIC) such as a 3d wand, for example to control navigation through has designed and produced a large scale, high resolution head- virtual worlds. tracked barrier-strip autostereoscopic display system that There are four main contributions of this paper. New virtual produces a VR immersive experience without requiring the user to barrier algorithms are presented that enhance image quality and wear any encumbrances. The resulting system, called Varrier, is a lower color shifts by operating at sub-pixel resolution. Automated passive parallax barrier 35-panel tiled display that produces a camera-based registration of the physical and virtual barrier strip wide field of view, head-tracked VR experience.
    [Show full text]
  • Stereogram Design for Testing Local Stereopsis
    Stereogram design for testing local stereopsis Gerald Westheimer and Suzanne P. McKee The basic ability to utilize disparity as a depth cue, local stereopsis, does not suffice to respond to random dot stereograms. They also demand complex perceptual processing to resolve the depth ambiguities which help mask their pattern from monocular recognition. This requirement may cause response failure in otherwise good stereo subjects and seems to account for the long durations of exposure required for target disparities which are still much larger than the best stereo thresholds. We have evaluated spatial stimuli that test local stereopsis and have found that targets need to be separated by at least 10 min arc to obtain good stereo thresholds. For targets with optimal separation of components and brief exposure duration (250 msec), thresh- olds fall in the range of 5 to 15 sec arc. Intertrial randomization of target lateral placement can effectively eliminate monocular cues and yet allow excellent stereoacuity. Stereoscopic acuity is less seriously affected by a small amount of optical defocus when target elements are widely, separated than when they are crowded, though in either case the performance decrement is higher than for ordinary visual acuity. Key words: stereoscopic acuity, local stereopsis, global stereopsis, optical defocus A subject is said to have stereopsis if he can are very low indeed, certainly under 10 sec detect binocular disparity of retinal images arc in a good observer, and such low values and associate the quality of depth with it. In can be attained with exposures of half a sec- its purest form this would manifest itself by ond or even less.
    [Show full text]
  • Evaluating Relative Impact of Vr Components Screen Size, Stereoscopy and Field of View on Spatial Comprehension and Presence in Architecture
    EVALUATING RELATIVE IMPACT OF VR COMPONENTS SCREEN SIZE, STEREOSCOPY AND FIELD OF VIEW ON SPATIAL COMPREHENSION AND PRESENCE IN ARCHITECTURE by Nevena Zikic Technical Report No.53 May 2007 Computer Integrated Construction Research Program The Pennsylvania State University ©Copyright University Park, PA, 16802 USA ABSTRACT In the last couple of years, computing technology has brought new approaches to higher education, particularly in architecture. They include simulations, multimedia presentations, and more recently, Virtual Reality. Virtual Reality (also referred to as Virtual Environment) is a computer generated three-dimensional environment which responds in real time to the activities of its users. Studies have been performed to examine Virtual Reality’s potential in education. Although the results point to the usefulness of Virtual Reality, recognition of what is essential and how it can be further adapted to educational purposes is still in need of research. The purpose of this study is to examine Virtual Reality components and assess their potential and importance in an undergraduate architectural design studio setting. The goal is to evaluate the relative contribution of Virtual Reality components: display and content variables, (screen size, stereoscopy and field of view; level of detail and level of realism, respectively) on spatial comprehension and sense of presence using a variable- centered approach in an educational environment. Examining the effects of these independent variables on spatial comprehension and sense of presence will demonstrate the potential strength of Virtual Reality as an instructional medium. This thesis is structured as follows; first, the architectural design process and Virtual Reality are defined and their connection is established.
    [Show full text]
  • Stereoscopy and Stereoscopic Viewing
    STEREOSCOPY AND STEREOSCOPIC VIEWING STEREOSCOPY Stereoscopy, or solid vision, is the term given to the following natural phenomenon: When a person looks simultaneously at two photographs that have been taken of the same scene from two viewpoints, viewing one photograph with each eye, he can see an image of the scene in three dimensions. Stereoscopic, or binocular, vision is the facility, which makes stereoscopy possible. Normal two-eyed vision is required for realizing and measuring depth by stereoscopy. Two primary clues are involved in stereoscopic vision. The first clue is the double-image phenomenon. A simple demonstration indicates what is meant by double vision. If a pencil is held 12 to 15 inch or 300 to 375 mm in front of the eyes and the gaze is fixed on a spot on a far wall, there will be two images of the pencil. The left image is formed by the right eye, and the right image is formed by the left eye. When the gaze is now concentrated on the pencil, two images of an object on the wall will be formed. The right image is formed by the right eye, and the left image is formed by the left eye. If, while the eyes are gazing at the wall, the pencil is moved away from the eyes and toward the wall, there would be a position of the pencil some where in front of the wall where the double image would disappear. Stereoscopic vision is not possible at distances closer than about 10 inch, unless the eyes are aided by lenses, because the normal eye cannot comfortably focus any closer.
    [Show full text]