13,228 research outputs found
Blur point versus indistinguishable point in assessment of accommodation: objective and subjective findings in early presbyopes
Aim: To measure the distance from the eye and the
refraction of the eye at the point at which print blurs
and the point at which it becomes unreadable.
Methods: Subjective accommodation in 7 early
presbyopic subjects (mean age 45 years), with no
additional near correction, was tested using 6/12
reduced Snellen and 6/12 Lea symbols. The point at
which blur was first noticed and the point at which
the print became indistinguishable were noted in
centimetres. Objective measures of refraction were
taken at each of these points.
Results: Subjective and objective results for reduced
Snellen and Lea symbols were similar ( p = 0.91;
p = 0.81) as were the points where the print was no
longer distinguishable ( p = 0.23; p = 0.72). The difference between the blur point and the indistinguishable
point measured in centimetres for both the
reduced Snellen text and Lea symbols were statistically
significant ( p = 0.005; p = 0.0001). The objective
measures for these points, however, were not
statistically different ( p = 0.32 and p = 0.63, respectively).
Conclusion: A clinically significant difference exists
in the distance from the eyes between the point at
which text blurs and the point at which it becomes
indistinguishable. No significant change occurs in
accommodation when measured objectively after the
blur point. It is recommended that the end point of
this test is the point at which print starts to blur
Edge-region grouping in figure-ground organization and depth perception.
Edge-region grouping (ERG) is proposed as a unifying and previously unrecognized class of relational information that influences figure-ground organization and perceived depth across an edge. ERG occurs when the edge between two regions is differentially grouped with one region based on classic principles of similarity grouping. The ERG hypothesis predicts that the grouped side will tend to be perceived as the closer, figural region. Six experiments are reported that test the predictions of the ERG hypothesis for 6 similarity-based factors: common fate, blur similarity, color similarity, orientation similarity, proximity, and flicker synchrony. All 6 factors produce the predicted effects, although to different degrees. In a 7th experiment, the strengths of these figural/depth effects were found to correlate highly with the strength of explicit grouping ratings of the same visual displays. The relations of ERG to prior results in the literature are discussed, and possible reasons for ERG-based figural/depth effects are considered. We argue that grouping processes mediate at least some of the effects we report here, although ecological explanations are also likely to be relevant in the majority of cases
Motion Deblurring in the Wild
The task of image deblurring is a very ill-posed problem as both the image
and the blur are unknown. Moreover, when pictures are taken in the wild, this
task becomes even more challenging due to the blur varying spatially and the
occlusions between the object. Due to the complexity of the general image model
we propose a novel convolutional network architecture which directly generates
the sharp image.This network is built in three stages, and exploits the
benefits of pyramid schemes often used in blind deconvolution. One of the main
difficulties in training such a network is to design a suitable dataset. While
useful data can be obtained by synthetically blurring a collection of images,
more realistic data must be collected in the wild. To obtain such data we use a
high frame rate video camera and keep one frame as the sharp image and frame
average as the corresponding blurred image. We show that this realistic dataset
is key in achieving state-of-the-art performance and dealing with occlusions
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Tracking the affective state of unseen persons.
Emotion recognition is an essential human ability critical for social functioning. It is widely assumed that identifying facial expression is the key to this, and models of emotion recognition have mainly focused on facial and bodily features in static, unnatural conditions. We developed a method called affective tracking to reveal and quantify the enormous contribution of visual context to affect (valence and arousal) perception. When characters' faces and bodies were masked in silent videos, viewers inferred the affect of the invisible characters successfully and in high agreement based solely on visual context. We further show that the context is not only sufficient but also necessary to accurately perceive human affect over time, as it provides a substantial and unique contribution beyond the information available from face and body. Our method (which we have made publicly available) reveals that emotion recognition is, at its heart, an issue of context as much as it is about faces
No-reference image quality assessment through the von Mises distribution
An innovative way of calculating the von Mises distribution (VMD) of image
entropy is introduced in this paper. The VMD's concentration parameter and some
fitness parameter that will be later defined, have been analyzed in the
experimental part for determining their suitability as a image quality
assessment measure in some particular distortions such as Gaussian blur or
additive Gaussian noise. To achieve such measure, the local R\'{e}nyi entropy
is calculated in four equally spaced orientations and used to determine the
parameters of the von Mises distribution of the image entropy. Considering
contextual images, experimental results after applying this model show that the
best-in-focus noise-free images are associated with the highest values for the
von Mises distribution concentration parameter and the highest approximation of
image data to the von Mises distribution model. Our defined von Misses fitness
parameter experimentally appears also as a suitable no-reference image quality
assessment indicator for no-contextual images.Comment: 29 pages, 11 figure
Hierarchical Star Formation in Nearby LEGUS Galaxies
Hierarchical structure in ultraviolet images of 12 late-type LEGUS galaxies
is studied by determining the numbers and fluxes of nested regions as a
function of size from ~1 to ~200 pc, and the number as a function of flux. Two
starburst dwarfs, NGC 1705 and NGC 5253, have steeper number-size and flux-size
distributions than the others, indicating high fractions of the projected areas
filled with star formation. Nine subregions in 7 galaxies have similarly steep
number-size slopes, even when the whole galaxies have shallower slopes. The
results suggest that hierarchically structured star-forming regions several
hundred parsecs or larger represent common unit structures. Small galaxies
dominated by only a few of these units tend to be starbursts. The
self-similarity of young stellar structures down to parsec scales suggests that
star clusters form in the densest parts of a turbulent medium that also forms
loose stellar groupings on larger scales. The presence of super star clusters
in two of our starburst dwarfs would follow from the observed structure if
cloud and stellar subregions more readily coalesce when self-gravity in the
unit cell contributes more to the total gravitational potential.Comment: 9 pages, 4 figures, accepted for ApJ
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