Parallel Processing of Luminance Steps in the Presence of Luminance Gradients

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 62-62 ◽  
Author(s):  
A Grodon ◽  
M Fahle
Keyword(s):  
Parallel Processing ◽  
Visual System ◽  
Human Visual System ◽  
Reaction Times ◽  
Step Size ◽  
Detection Thresholds ◽  
Imaginary Circle ◽  
Staircase Procedure ◽  
Dark Background ◽  
Spatial Changes

Some features of complex visual displays are analysed effortlessly and in parallel by the human visual system, without requiring scrutiny. Examples for such features are changes of luminance, colour, orientation, and movement. We measured thresholds as well as reaction times for the detection of abrupt spatial changes in luminance in the presence of luminance gradients, in order to evaluate the ability of the system to ignore such gradients. Stimuli were presented on a 20 inch monitor under control of a Silicon Graphics workstation. Luminance was calibrated by means of a photometer (Minolta). We presented between 4 and 14 rectangles simultaneously on a homogeneous dark background. Rectangles were arranged on an incomplete, imaginary circle around the fixation point and luminance changed stepwise from one rectangle to the next. Five observers had to indicate whether all luminance steps between the rectangles were subjectively equal or whether one luminance step was larger. Detection thresholds were determined for the larger step as a function of the small steps (‘base step size’) by means of an adaptive staircase procedure. The smallest luminance steps were detected when the base step size was zero and when only few rectangles were presented. Thresholds increased slightly with the number of rectangles displayed simultaneously, and to a greater extent (by up to a factor of 2) with increasing base step size. The results of all observers improved significantly through practice, by about a factor of 2. We conclude that the visual system is unable to completely eliminate gradients of luminance and to isolate sharp transitions in luminance.

Technology Study on the Different Cognitive Process of Stereopsis between Crossed and Uncrossed Fine Disparity

2014 ◽  
Vol 886 ◽  
pp. 374-377
Author(s):  
Yan Wu ◽  
Qi Li
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Cognitive Process ◽  
Three Dimensional ◽  
Reaction Times ◽  
Visual Fatigue ◽  
Technology Study ◽  
Random Dot Stereograms ◽  
Display Technology ◽  
Made In

Considerable improvements in display technology were made in stereoscopic imaging and image quality rose with technical progress. But there was not enough effort on reducing visual fatigue. The study was to investigate one of the ways to reduce visual fatigue caused by three-dimensional images. Static random-dot stereograms (RDS) were used as stimuli. The performance of every subject was recorded with disparate disparities of 3.27', 6.54', 8.18', 11.45', 14.72', 17.99', 21.26', and 24.53'. Results showed that reaction times were always longer in the uncrossed disparities relative to the crossed disparities. For crossed disparities, human visual system was the most sensitive to the images with disparity of 6.54'. As to uncrossed disparities, human visual system was the most sensitive to the images with disparity of 8.18'.

scholarly journals Perceptual Proxies of Visual Comparison

2019 ◽  
Author(s):  
Nicole Jardine ◽  
Brian Ondov ◽  
Niklas Elmqvist ◽  
Steven Franconeri
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Human Performance ◽  
Explanatory Power ◽  
Empirical Evaluation ◽  
Empirical Work ◽  
Staircase Procedure ◽  
Data Comparison ◽  
Visual Comparison ◽  
Simple Models

Perceptual tasks in visualizations often involve comparisons. Of two sets of values depicted in two charts, which set had values that were the highest overall? Which had the widest range? Prior empirical work found that the performance on different visual comparison tasks (e.g., “biggest delta”, “biggest correlation”) varied widely across different combinations of marks and spatial arrangements. In this paper, we expand upon these combinations in an empirical evaluation of two new comparison tasks: the“biggest mean” and “biggest range” between two sets of values. We used a staircase procedure to titrate the difficulty of the data comparison to assess which arrangements produced the most precise comparisons for each task. We find visual comparisons of biggest mean and biggest range are supported by some chart arrangements more than others, and that this pattern is substantially different from the pattern for other tasks. To synthesize these dissonant findings, we argue that we must understand which features of a visualization are actually used by the human visual system to solve a given task. We call these perceptual proxies. For example, when comparing the means of two bar charts, the visual system might use a “Mean length” proxy that isolates the actual lengths of the bars and then constructs a true average across these lengths. Alternatively, it might use a “Hull Area” proxy that perceives an implied hull bounded by the bars of each chart and then compares the areas of these hulls. We propose a series of potential proxies across different tasks, marks, and spatial arrangements. Simple models of these proxies can be empirically evaluated for their explanatory power by matching their performance to human performance across these marks, arrangements, and tasks. We use this process to highlight candidates for perceptual proxies that might scale more broadly to explain performance in visual comparison.

Disparity-tuned channels of the human visual system

1993 ◽  
Vol 10 (4) ◽  
pp. 585-596 ◽  
Author(s):  
Lawrence K. Cormack ◽  
Scott B. Stevenson ◽  
Clifton M. Schor
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Single Unit ◽  
Binocular Disparity ◽  
Random Element ◽  
Stereoscopic Depth ◽  
Detection Thresholds ◽  
Strict Adherence ◽  
Low Level ◽  
Single Unit Recordings

AbstractTraditionally, it has been thought that the processing of binocular disparity for the perception of stereoscopic depth is accomplished via three types of disparity-selective channels – “near,” “far,” and “tuned.” More recent evidence challenges this notion. We have derived disparity-tuning functions psychophysically using a subthreshold summation (i.e. low-level masking) technique. We measured correlation-detection thresholds for dynamic random-element stereograms containing either one or two surfaces in depth. The resulting disparity-tuning functions show an opponent-type profile, indicating the presence of inhibition between disparity-tuned units in the visual system. Moreover, there is clear inhibition between disparities of the same sign, obviating a strict adherence to near-far opponency. These results compare favorably with tuning functions derived psychophysically using an adaptation technique, and with the tuning profiles from published single-unit recordings. Our results suggests a continuum of overlapping disparity-tuned channels, which is consistent with recent physiological evidence as well as models based on other psychophysical data.

A Study on the Cognitive Process of Stereopsis in Small Uncrossed Disparity

2014 ◽  
Vol 513-517 ◽  
pp. 3655-3658
Author(s):  
Yan Wu ◽  
Qi Li
Keyword(s):  
Visual System ◽  
Human Visual System ◽  
Cognitive Process ◽  
Reaction Times ◽  
Normal Subjects ◽  
Stereo Images ◽  
Uncrossed Disparity ◽  
Random Dot Stereograms

Static random-dot stereograms (RDS) were used as stimuli to investigate the uncrossed disparity in 15 normal subjects. The response of every subject was recorded with different disparities of 3.27 arc min, 6.54 arc min, 8.18 arc min, 11.45 arc min, 14.72 arc min, 17.99 arc min, 21.26 arc min and 24.53 arc min. The results showed that the human visual system was the most sensitive to stereo images at disparity of 8.18 arc min. Disparity of 21.26 arc min had significant differences with other small disparities in reaction times, as supported the viewpoint that it was reasonable to limit the fine disparity in 20 arc min.

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