51 research outputs found
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When stuff gets old: material surface characteristics and the visual perception of material change over time
YesMaterialsâ surfaces change over time due to chemical and physical processes. These processes can significantly alter a materialâs visual appearance, yet we can recognise the material as the same. The present study examined the extent of changes the human visual system can detect in specific materials over time. Participants (NâŻ=âŻ5) were shown images of different materials (Banana, Copper, Leaf) from an existing calibrated set of photographs. Participants indicated which image pair (of the 2 pairs shown) displayed the largest difference. Estimated perceptual scales showed that observers were able to rank the images of aged materials systematically. Next, we examined the role that global and local changes in material surface colour play in the perception of material change. We altered the information about colour and geometrical distribution in the images used in the first experiment, and participants repeated the task with the altered images. Our results showed significant differences between individual observers. Most importantly, participantsâ ability to rank the images varied with material type. The leaf images were particularly affected by our alteration of the geometrical distribution. Together, our findings show the factors contributing to the perception of material change over time.This work was supported by the European Unionâs Horizon 2020 research and innovation programme [Grant Agreement No 765121]
Understanding images in biological and computer vision
yesThis issue of Interface Focus is a collection of papers arising out of a Royal Society Discussion meeting entitled âUnderstanding images in biological and computer visionâ held at Carlton Terrace on the 19th and 20th February, 2018. There is a strong tradition of inter-disciplinarity in the study of visual perception and visual cognition. Many of the great natural scientists including Newton [1], Young [2] and Maxwell (see [3]) were intrigued by the relationship between light, surfaces and perceived colour considering both physical and perceptual processes. Brewster [4] invented both the lenticular stereoscope and the binocular camera but also studied the perception of shape-from-shading. More recently, Marr's [5] description of visual perception as an information processing problem led to great advances in our understanding of both biological and computer vision: both the computer vision and biological vision communities have a Marr medal. The recent successes of deep neural networks in classifying the images that we see and the fMRI images that reveal the activity in our brains during the act of seeing are both intriguing. The links between machine vision systems and biology may at sometimes be weak but the similarity of some of the operations is nonetheless striking [6].
This two-day meeting brought together researchers from the fields of biological and computer vision, robotics, neuroscience, computer science and psychology to discuss the most recent developments in the field. The meeting was divided into four themes: vision for action, visual appearance, vision for recognition and machine learning
Learning a 3-D Visual Light Field: Effects of Exploration on Lightness Constancy
The pattern of light across a scene is determined by the lighting, the material properties of objects in the scene, and the three- dimensional (3-D) scene structure. The problem of determining the material properties of an object is therefore a complex one. To do this correctly the relationship between 3-D scene structure and lighting must be understood by the viewer. In this paper we describe experiments which evaluate how exploration of the lightfield [1] within the scene aids the estimation of surface lightness (albedo). We find that the experience of viewing a block moving throughout the 3D scene - illustrating the variations in lightfield â results in lightness constancy, i.e. viewers are able to estimate surface albedo under varying illumination. Exploration of the lightfield facilitated albedo recovery as opposed to simple brightness matching. This record was migrated from the OpenDepot repository service in June, 2017 before shutting down
The many colours of âthe dressâ
YesThere has been an intense discussion
among the public about the colour
of a dress, shown in a picture posted
originally on Tumblr (http://swiked.
tumblr.com/post/112073818575/
guys-please-help-me-is-this-dress
white-and; accessed on 10:56 am
GMT on Tue 24 Mar 2015). Some
people argue that they see a white
dress with golden lace, while others
describe the dress as blue with black
lace. Here we show that the question
âwhat colour is the dress?â has more
than two answers.The full text was made available at the end of the publisher's embargo, 14th May 201
Sensitivity to velocity- and disparity based cues to motion-in-depth with and without spared stereopsis in binocular visual impairment
YesPurpose: Two binocular sources of information serve motion-in-depth (MID) perception:
changes in disparity over time (CD), and interocular velocity differences (IOVD). While CD
requires the computation of small spatial disparities, IOVD could be computed from a much
lower-resolution signal. IOVD signals therefore might still be available under conditions of
binocular vision impairment (BVI) with limited or no stereopsis, e.g. amblyopia.
Methods: Sensitivity to CD and IOVD was measured in adults who had undergone therapy
to correct optical misalignment or amblyopia in childhood (n=16), as well as normal vision
controls with good stereoacuity (n=8). Observers discriminated the interval containing a
smoothly-oscillating MID âtestâ stimulus from a âcontrolâ stimulus in a two-interval forced
choice (2IFC) paradigm.
Results: Of the BVI observers with no static stereoacuity (n=9), one displayed evidence for
sensitivity to IOVD only, while there was otherwise no sensitivity for either CD or IOVD in
the group. Generally, BVI observers with measurable stereoacuity (n=7) displayed a pattern
resembling the control group: showing a similar sensitivity for both cues. A neutral-density
(ND) filter placed in front of the fixing eye in a subset of BVI observers did not improve
performance.
Conclusions: In one BVI observer there was preserved sensitivity to IOVD but not CD,
though overall only those BVI observers with at least gross stereopsis were able to detect
disparity-based or velocity-based cues to MID. The results imply that these logically distinct
information sources are somehow coupled, and in some cases BVI observers with no
stereopsis may still retain sensitivity to IOVD.UK Biotechnology and Biological 498 Sciences Research Council (BBSRC): BB/M002543/1 (Alex R. Wade) BB/M001660/1 (Julie 499 M. Harris) and BB/M001210/1 (Marina Bloj
Ambiguity in high definition: Gaze determines physical interpretation of ambiguous rotation even in the absence of a visual context
YesPhysical interactions between objects, or between an object and the ground, are amongst the most biologically relevant for live beings. Prior knowledge of Newtonian physics may play a role in disambiguating an objectâs movement as well as foveation by increasing the spatial resolution of the visual input. Observers were shown a virtual 3D scene, representing an ambiguously rotating ball translating on the ground. The ball was perceived as rotating congruently with friction, but only when gaze was located at the point of contact. Inverting or even removing the visual context had little influence on congruent judgements compared with the effect of gaze. Counterintuitively, gaze at the point of contact determines the solution of perceptual ambiguity, but independently of visual context. We suggest this constitutes a frugal strategy, by which the brain infers dynamics locally when faced with a foveated input that is ambiguous.J.S. was funded by a College of Life Sciences studentship from the University of Leicester
The effect of adherence to spectacle wear on early developing literacy: a longitudinal study based in a large multi-ethnic city, Bradford, UK
YesObjectives: To determine the impact of adherence to
spectacle wear on visual acuity (VA) and developing
literacy following vision screening at age 4â5 years.
Design: Longitudinal study nested within the Born in
Bradford birth cohort.
Setting and participants: Observation of 944 children:
432 had failed vision screening and were referred
(treatment group) and 512 randomly selected (comparison
group) who had passed (<0.20 logarithm of the minimum
angle of resolution (logMAR) in both eyes). Spectacle wear
was observed in school for 2 years following screening
and classified as adherent (wearing spectacles at each
assessment) or non-adherent.
Main outcome measures: Annual measures of VA
using a crowded logMAR test. Literacy was measured by
Woodcock Reading Mastery Tests-Revised subtest: letter
identification.
Results: The VA of all children improved with increasing
age, â0.009 log units per month (95% CI â0.011 to
â0.007) (worse eye). The VA of the adherent group
improved significantly more than the comparison group, by
an additional â0.008 log units per month (95% CI â0.009
to â0.007) (worse eye) and â0.004 log units per month
(95% CI â0.005 to â0.003) in the better eye. Literacy was
associated with the VA, letter identification (ID) reduced
by â0.9 (95% CI â1.15 to â0.64) for every one line (0.10
logMAR) fall in VA (better eye). This association remained
after adjustment for socioeconomic and demographic
factors (â0.33, 95% CI â0.54 to â0.12). The adherent
group consistently demonstrated higher letter-ID scores
compared with the non-adherent group, with the greatest
effect size (0.11) in year 3.
Conclusions: Early literacy is associated with the level of
VA; children who adhere to spectacle wear improve their
VA and also have the potential to improve literacy. Our
results suggest failure to adhere to spectacle wear has
implications for the childâs vision and education.AB is funded by a National Institute for Health Research Post- Doctoral Fellowship Award (PDF-2013-06-050). The Born in Bradford study presents independent research commissioned by the National Institute for Health Research Collaboration for Applied Health Research and Care (NIHR CLAHRC) and the Programme Grants for Applied Research funding scheme (RP-PG-0407-10044)
Prevalence of, and Risk Factors for, Presenting Visual Impairment : Findings from a vision screening programme based on UK NSC guidance in a multi-ethnic population
YesPurpose:
To determine presenting visual acuity levels and explore the factors associated with failing vision screening in a multi-ethnic population of UK children aged 4â5 years.
Methods:
Visual acuity (VA) using the logMAR Crowded Test was measured in 16,541 children in a population-based vision screening programme. Referral for cycloplegic examination was based on national recommendations (>0.20logMAR in one or both eyes). Presenting visual impairment (PVI) was defined as VA >0.3logMAR in the better eye. Multivariable logistic regression was used to assess the association of ethnicity, maternal, and early-life factors with failing vision screening and PVI in participants of the Born in Bradford birth cohort.
Results:
In total, 2467/16,541 (15%) failed vision screening, 732 (4.4%) had PVI. Children of Pakistani (OR: 2.49; 95% CI: 1.74â3.60) and other ethnicities (OR: 2.00; 95% CI: 1.28â3.12) showed increased odds of PVI compared to white children. Children born to older mothers (OR: 1.63; 95% CI: 1.19â2.24) and of low birth weight (OR: 1.52; 95% CI: 1.00â2.34) also showed increased odds. Follow-up results were available for 1068 (43.3%) children, 993 (93%) were true positives; 932 (94%) of these had significant refractive error. Astigmatism (>1DC) (44%) was more common in children of Pakistani ethnicity and hypermetropia (>3.0DS) (27%) in white children (Fisherâs exact, pâ<â0.001).
Conclusions:
A high prevalence of PVI is reported. Failing vision screening and PVI were highly associated with ethnicity. The positive predictive value of the vision screening programme was good, with only 7% of children followed up confirmed as false positives.National Institute for Health Research Post-Doctoral Fellowship Award (PDF-2013-06-050); The Born in Bradford study presents independent research commissioned by the National Institute for Health Research Collaboration for Applied Health Research and Care (NIHR CLAHRC) and the Programme Grants for Applied Research funding scheme (RP-PG-0407-10044)
Bias effects of short- and long-term color memory for unique objects
Are objects remembered with a more saturated color? Some of the evidence supporting this statement comes from research using âmemory colorsââthe typical colors of particular objects, for example, the green of grass. The problematic aspect of these findings is that many different exemplars exist, some of which might exhibit a higher saturation than the one measured by the experimenter. Here we avoid this problem by using unique personal items and comparing long- and short-term color memory matches (in hue, value, and chroma) with those obtained with the object present. Our results, on average, confirm that objects are remembered as more saturated than they are
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