Psychophysical Studies Of Binocular Interactions In Humans

Psychophysical investigations of binocular interactions have shown that there are at least two binocular channels in the human visual system. In addition to an interocular channel that responds to input to either eye, there is evidence of a binocular channel that acts as a logical AND-gate. This second binocular mechanism will only respond to simultaneous stimulation of both eyes with similar images. Support for the existence of this \u27AND\u27 mechanism has been provided by adaptation (Wolfe & Held, 1981, 1982; Wilcox, Timney, & St. John, 1990), and detection experiments (Cohn & Lasley, 1976; Cogan, 1987).;In predicting the results of adaptation experiments several investigators have adopted a \u27neural averaging\u27 hypothesis which proposes that the output from all available monocular and binocular channels is averaged to produce the final percept. Experiments I and II evaluated this suggestion and a second proposal that all channels are independent, and that detection is mediated by the most sensitive of these channels. The results of both studies showed that there is interaction between the neural channels.;While there is convincing support for the existence of an AND channel, little is known about its response characteristics. Experiments III through V examined the temporal aspects, threshold sensitivity, and interocular spatial phase sensitivity, of an AND mechanism. Collectively, these experiments support the assumption that the AND channel requires binocular stimuli that are similar along a number of dimensions. The final experiment investigated a potential functional role of the AND mechanism in human vision. In this study, both adaptation and subthreshold summation procedures were used to assess the contribution of the AND channel to binocular summation. The results demonstrated that an AND mechanism makes a significant contribution to binocular summation.;It has been argued previously (Wolfe, 1986) that an AND mechanism is important to stereoscopic vision. Given Wolfe\u27s assertions and the results of Experiment VI, it appears that the output of the AND channel is not necessarily restricted to a single process, but could contribute to several visual tasks, including binocular summation and stereopsis

When stereopsis does not improve with increasing contrast1Portions of this work were presented at The European Conference on Visual Perception, Helsinki, 1997.1

AbstractIt is well known that stereoacuity for conventional (1st-order) stimuli improves with increasing contrast with an approximate slope of −0.5 on log–log axes (Halpern DL, Blake RR. Perception 1988;17:483–495; Legge GE, Gu Y. Vis Res 1989;29:989–1004). In the experiments reported here a variety of stimuli were used (Gabor patches, amplitude modulated stimuli and 1D noise patches) and tasks (stereoacuity and Dmax) to determine if 2nd-order stereopsis shows a similar square root dependence. The results consistently demonstrate that the effect of contrast on stereopsis is quite different for the 2nd-order stimuli. Increases in stimulus contrast have little effect on performance; the resulting slopes are very shallow. The pattern of results is similar when the interocular contrast ratio is varied, demonstrating that 2nd-order processing is more resilient to stimulus differences in the two eyes than 1st-order

The effects of blur and size on monocular and stereoscopic localization

AbstractMonocular localization of non-abutting stimuli and stereoscopic localization of the same second-order targets are performed with the same precision (Wilcox, L.M. & Hess, R.F. (1996) Is the site of non-linear filtering in stereopsis before or after binocular combination? Vision Research, 36, 391–399). Further, both tasks show a similar dependence on the scale of the stimulus. Since prior studies used Gaussian-enveloped stimuli, modifications of stimulus scale produced concurrent changes in edge blur. The experiments reported here assess the relative contributions of size and blur to the observed dependence on envelope scale for both monocular localization and stereoacuity. Stereoacuity for first-order targets was found to be an order of magnitude better than stereoacuity for second-order targets and monocular acuity for both first- and second-order targets. Further, while first-order stereopsis was found to depend solely on blur, second-order stereoacuity and monocular acuity were affected by both size and blur. These results suggest that while stereoacuity for first-order stimuli may be determined by a correlative process limited by early additive noise, stereoacuity for second-order stimuli and monocular acuity for non-abutting targets are more likely limited by stimulus-dependent spatial subsampling

Surface slant impairs disparity discontinuity discrimination

Binocular disparity signals are highly informative about the three-dimensional structure of visual scenes, including aiding the detection of depth discontinuities between surfaces. Here, we examine factors affecting sensitivity to such surface discontinuities. Participants were presented with random dot stereograms depicting two planar surfaces slanted in opposite directions and were asked to judge the sign of the depth discontinuity created where those surfaces met. Although the judgement was focussed on the adjacent edges, the precision of depth discontinuity discrimination depended upon the slant of the two surfaces: increasing surface slants to ±60° increased discontinuity discrimination thresholds by, on average, a factor of 5. Control experiments examining discontinuity discrimination across surfaces with identical slants showed either biases in discontinuity judgements or reduced threshold elevation. These results suggest that sensitivity to depth discontinuities is affected by processing limitations in both local absolute disparity measurement mechanisms and mechanisms selective for disparity differences. As further evidence in support of this conclusion, we show that our results are well-described by a model of discontinuity discrimination based on the encoding of local differences in relative disparity

Paper: Expert Viewers\u27 Preferences for Higher Frame Rate 3D Film

Recently the movie industry has been advocating the use of frame rates significantly higher than the traditional 24 frames per second. This higher frame rate theoretically improves the quality of motion portrayed in movies, and helps avoid motion blur, judder and other undesirable artifacts. Previously we reported that young adult audiences showed a clear preference for higher frame rates, particularly when contrasting 24 fps with 48 or 60 fps. We found little impact of shutter angle (frame exposure time) on viewers’ choices. In the current study we replicated this experiment with an audience composed of imaging professionals who work in the film and display industry who assess image quality as an aspect of their everyday occupation. These viewers were also on average older and thus could be expected to have attachments to the “film look” both through experience and training. We used stereoscopic 3D content, filmed and projected at multiple frame rates (24, 48 and 60 fps), with shutter angles ranging from 90◦ to 358◦, to evaluate viewer preferences. In paired-comparison experiments we assessed preferences along a set of five attributes (realism, motion smoothness, blur/clarity, quality of depth and overall preference). As with the young adults in the earlier study, the expert viewers showed a clear preference for higher frame rates, particularly when contrasting 24 fps with 48 or 60 fps. We found little impact of shutter angle on viewers’ choices, with the exception of one clip at 48 fps where there was a preference for larger shutter angle. However, this preference was found for the most dynamic “warrior” clip in the experts but in the slower moving “picnic” clip for the naïve viewers. These data confirm the advantages afforded by high-frame rate capture and presentation in a cinema context in both naïve audiences and experienced film professionals.https://source.sheridancollege.ca/centres_sirt_works/1002/thumbnail.jp

Evidence that Viewers Prefer Higher Frame Rate Film

High frame rate (HFR) movie-making refers to the capture and projection of movies at frame rates several times higher than the traditional 24 frames per second. This higher frame rate theoretically improves the quality of motion portrayed in movies, and helps avoid motion blur, judder and other undesirable artefacts. However, there is considerable debate in the cinema industry regarding the acceptance of HFR content given anecdotal reports of hyper-realistic imagery that reveals too much set and costume detail. Despite the potential theoretical advantages, there has been little empirical investigation of the impact of high-frame rate techniques on the viewer experience. In this study we use stereoscopic 3D content, filmed and projected at multiple frame rates (24, 48 and 60 fps), with shutter angles ranging from 90 degrees to 358 degrees, to evaluate viewer preferences. In a paired-comparison paradigm we assessed preferences along a set of five attributes (realism, motion smoothness, blur/clarity, quality of depth and overall preference). The resulting data show a clear preference for higher frame rates, particularly when contrasting 24 fps with 48 or 60 fps. We found little impact of shutter angle on viewers’ choices, with the exception of one measure (motion smoothness) for one clip type. These data are the first empirical evidence of the advantages afforded by high frame rate capture and presentation in a cinema context.https://source.sheridancollege.ca/centres_sirt_works/1000/thumbnail.jp

3D display size matters: Compensating for the perceptual effects of S3D display scaling

Abstract Introduction In recent years the consumer electronics market has been flooded with a variety of S3D products, which rely on a variety of display and image segregation technologies. For each display system, the ideal viewing conditions (eg. viewing angle) can be defined in order to obtain the desired 3D experience. SMPTE and THX [1, 2] have provided specific standards and guidelines for the ideal viewing angle for theatre and television. However, screen dimension 1 is an uncontrolled variable since the same content could be displayed on a mobile autostereoscopic device, 3D monitor, HD 3DTV or in a 3D movie theatre. Adapting a S3D film to a variety of screen sizes is necessary for most, if not all, popular movies if the distributors are to maximize their exposure and therefore earnings. However, unlike 2D film the S3D scaling process is complicated by a variety of 1 The range of viewing distances typically used are correlated with the size of the display, with audiences moving closer as screens get smaller. If field of view is constant it is often the distance that is more important. Since they normally co-vary here we will focus on screen size and related disparity scaling issues, but will point out the role of viewing distance in particular when it is warranted. computational and perceptual issues that can significantly impact the audience experience. As outlined below, the existing approaches to scaling S3D content for a variety of delivery form factors can be divided into two main categories: those applied during acquisition and those applied during postproduction or display. The most common strategy is some combination of pre and post-production approaches. However, inevitably some degree of perceptual and geometric distortion will remain. A better understanding of these distortions and their perceptual consequences will provide S3D content creators with insight and context for using sophisticated scaling approaches based on both acquisition and post-production techniques. This paper will review the principal issues related to S3D content scaling, some of the technical solutions available to content makers/ providers and the perceptual consequences for audiences. Stereoscopic Geometry As was shown by Spottiswood in the early 1950's [3], displaying stereoscopic 3D content at different sizes may dramatically influence the audience's S3D experience. Given the interdependence of acquisition and display parameters; most filmmakers, while trying to protect for different screen dimensions will have a target viewing condition when they begin filming. Figures 1 and 2 depict stereoscopic viewing and acquisition geometry, respectivel

Evidence of gene-environment interaction for two genes on chromosome 4 and environmental tobacco smoke in controlling the risk of nonsyndromic cleft palate

Nonsyndromic cleft palate (CP) is one of the most common human birth defects and both genetic and environmental risk factors contribute to its etiology. We conducted a genome-wide association study (GWAS) using 550 CP case-parent trios ascertained in an international consortium. Stratified analysis among trios with different ancestries was performed to test for GxE interactions with common maternal exposures using conditional logistic regression models. While no single nucleotide polymorphism (SNP) achieved genome-wide significance when considered alone, markers in SLC2A9 and the neighboring WDR1 on chromosome 4p16.1 gave suggestive evidence of gene-environment interaction with environmental tobacco smoke (ETS) among 259 Asian trios when the models included a term for GxE interaction. Multiple SNPs in these two genes were associated with increased risk of nonsyndromic CP if the mother was exposed to ETS during the peri-conceptual period (3 months prior to conception through the first trimester). When maternal ETS was considered, fifteen of 135 SNPs mapping to SLC2A9 and 9 of 59 SNPs in WDR1 gave P values approaching genome-wide significance (10-6<P<10-4) in a test for GxETS interaction. SNPs rs3733585 and rs12508991 in SLC2A9 yielded P = 2.26×10-7 in a test for GxETS interaction. SNPs rs6820756 and rs7699512 in WDR1 also yielded P = 1.79×10-7 and P = 1.98×10-7 in a 1 df test for GxE interaction. Although further replication studies are critical to confirming these findings, these results illustrate how genetic associations for nonsyndromic CP can be missed if potential GxE interaction is not taken into account, and this study suggest SLC2A9 and WDR1 should be considered as candidate genes for CP. © 2014 Wu et al