scholarly journals Measuring perceptual scales of perceived surface lightness: a comparison between MLDS and matching

2016 ◽  
Vol 16 (12) ◽  
pp. 817
Author(s):  
Christiane Wiebel ◽  
Guillermo Aguilar ◽  
Marianne Maertens
Keyword(s):  
Surface Lightness

scholarly journals Testing the role of Michelson contrast for the perception of surface lightness

2016 ◽  
Vol 16 (11) ◽  
pp. 17 ◽  
Author(s):  
Christiane B. Wiebel ◽  
Manish Singh ◽  
Marianne Maertens
Keyword(s):  
Surface Lightness

scholarly journals Diamond Patterns: Cumulative Cornsweet Effects and Motion-Induced Brightening

i-Perception ◽  
2018 ◽  
Vol 9 (4) ◽  
pp. 204166951877069 ◽  
Author(s):  
Patrick Cavanagh ◽  
Stuart Anstis
Keyword(s):  
Cumulative Effect ◽  
Mean Luminance ◽  
Surface Lightness

A Cornsweet edge creates the perception of a step in surface lightness between two adjacent regions of identical mean luminance due to a gradient on both sides. We might imagine that in a concatenated set of these gradients, the lightness steps would accumulate, but they do not. However, a diamond pattern, with each diamond filled with an identical luminance gradient does give a cumulative Cornsweet effect. Here, we offer an illumination explanation for why the cumulative effect is visible in the diamonds but not in the basic ramp grating and we demonstrate that when the diamonds drift, they produce a strong brightening effect (depending on the direction of the motion) and a dimming aftereffect. These effects are consistent with the local luminance gradients and not with the global lightness shift of the cumulative Cornsweet effect.

Anchoring of Surface Lightness by Area and Luminance

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 153-153
Author(s):  
A L Gilchrist
Keyword(s):  
Relative Area ◽  
Stimulus Contrast ◽  
Lightness Perception ◽  
Empirical Results ◽  
Average Luminance ◽  
The Many ◽  
Surface Lightness ◽  
Luminance Range

Relative luminance is fundamental to lightness perception, but can be used to predict specific lightness values only when coupled with an anchoring rule. Empirical results indicate that, in simple displays, lightness is anchored by the highest luminance (white) rather than by the average luminance (middle gray). This implies that increasing the luminance range of a stimulus causes grayness induction: the lower luminance values become darker gray while the highest luminance remains unchanged, as many so-called brightness induction experiments have shown. Yet sometimes increasing the luminance range of a stimulus causes luminosity induction: the highest luminance becomes increasingly self-luminous while the lowest luminances remain unchanged. Whether grayness induction or luminosity induction results from an increase in stimulus contrast depends on relative area. A few simple, yet hitherto unrecognised, rules that describe how anchoring by highest luminance combines with anchoring by largest area appear to be consistent with the many published reports on area and lightness/brightness. These findings add to the accumulating evidence that many phenomena previously attributed to contrast are much better understood in terms of anchoring.

Lightness Constancy: A Direct Test of the Illumination-Estimation Hypothesis

2002 ◽  
Vol 13 (2) ◽  
pp. 142-149 ◽  
Author(s):  
M.D. Rutherford ◽  
D.H. Brainard
Keyword(s):  
Visual System ◽  
Color Constancy ◽  
The Other ◽  
Color Appearance ◽  
Direct Test ◽  
Illumination Estimation ◽  
Test Patch ◽  
Lightness Constancy ◽  
Surface Lightness

Many models of color constancy assume that the visual system estimates the scene illuminant and uses this estimate to determine an object's color appearance. A version of this illumination-estimation hypothesis, in which the illuminant estimate is associated with the explicitly perceived illuminant, was tested. Observers made appearance matches between two experimental chambers. Observers adjusted the illumination in one chamber to match that in the other and then adjusted a test patch in one chamber to match the surface lightness of a patch in the other. The illumination-estimation hypothesis, as formulated here, predicted that after both matches the luminances of the light reflected from the test patches would be identical. The data contradict this prediction. A second experiment showed that manipulating the immediate surround of a test patch can affect perceived lightness without affecting perceived illumination. This finding also falsifies the illumination-estimation hypothesis.

scholarly journals Surface color perception in three-dimensional scenes

2006 ◽  
Vol 23 (3-4) ◽  
pp. 311-321 ◽  
Author(s):  
HUSEYIN BOYACI ◽  
KATJA DOERSCHNER ◽  
JACQUELINE L. SNYDER ◽  
LAURENCE T. MALONEY
Keyword(s):  
Visual System ◽  
Recent Work ◽  
Human Visual System ◽  
Light Field ◽  
Three Dimensional ◽  
Color Perception ◽  
Line Of Sight ◽  
Surface Color ◽  
Matte Surface ◽  
Surface Lightness

Researchers studying surface color perception have typically used stimuli that consist of a small number of matte patches (real or simulated) embedded in a plane perpendicular to the line of sight (a “Mondrian,” Land & McCann, 1971). Reliable estimation of the color of a matte surface is a difficult if not impossible computational problem in such limited scenes (Maloney, 1999). In more realistic, three-dimensional scenes the difficulty of the problem increases, in part, because the effective illumination incident on the surface (the light field) now depends on surface orientation and location. We review recent work in multiple laboratories that examines (1) the degree to which the human visual system discounts the light field in judging matte surface lightness and color and (2) what illuminant cues the visual system uses in estimating the flow of light in a scene.

Cross-Sensory Correspondences and Naive Conceptions of Natural Phenomena

Perception ◽  
10.1068/p7195 ◽  
2012 ◽  
Vol 41 (5) ◽  
pp. 620-622 ◽  
Author(s):  
Peter Walker
Keyword(s):  
Free Fall ◽  
Natural Phenomena ◽  
Surface Lightness

Cross-sensory correspondences automatically intrude on performance in elaborate laboratory tasks (see Spence 2011 Attention, Perception, & Psychophysics73 971–995, for a review). Outside such tasks, might they be responsible for some popular misconceptions about natural phenomena? Four simple demonstrations reveal how the correspondences between surface-lightness and weight, and between surface-lightness and auditory pitch, generate misconceptions about the weight and movement of objects and the vocalisations of animals. Specifically, people expect darker objects to be heavier than lighter-coloured objects, to free-fall more quickly, to roll across a table more slowly, and to make lower-pitched vocalisations when they come to life.

scholarly journals The Effect of the Application of Edible Coatings on or before Ultraviolet Treatment on Postharvested Longan Fruits

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Mee Gie Lin ◽  
Ola Lasekan ◽  
Nazamid Saari ◽  
Siti Khairunniza-Bejo
Keyword(s):  
Weight Loss ◽  
Respiration Rate ◽  
Cell Structure ◽  
Enzymatic Activities ◽  
Total Phenolic ◽  
Uv Treatment ◽  
Browning Index ◽  
Chitosan Coating ◽  
Ultraviolet Treatment ◽  
Surface Lightness

This study compared the effect of application of edible coating on or before ultraviolet treatment on postharvest longan fruits. The treated longan fruits were examined for weight loss, respiration rate, surface color changes, enzymatic activities (PPO, POD, and PAL), and total phenolic contents throughout the 7 storage days at ambient temperature. In addition, coat homogeneity was examined and cell structure of longan flesh at the end of storage was observed. The results showed that when UV was applied before coating (i.e., chitosan or carrageenan), it had relatively lower PPO and PAL activities and retained higher TPC in longan pericarp. However, the changes in enzymatic activities did not affect the surface lightness and browning index as they were more influenced by the type of coating, in which combination treatments with carrageenan showed higher surface lightness and lower browning index compared to treatment combinations containing chitosan. However, when UV treatment preceded coating, the combinations of UV plus chitosan coating produced lower PPO and PAL activities and retained better cell structure with less damage than the combinations of UV plus carrageenan coating. UV plus carrageenan coating showed relatively higher weight loss and respiration rate, with cell structure exhibiting bigger intercellular spaces at the end of storage. Therefore, application of UV treatment followed by chitosan coating was found to be the best treatment combination for controlling enzymatic activities and reducing senescence rate of longan fruits.

Lightness Perception Can Be Affected by Surface Curvature from Stereopsis

Perception ◽  
1994 ◽  
Vol 23 (8) ◽  
pp. 869-881 ◽  
Author(s):  
David Buckley ◽  
John P Frisby ◽  
Jonathan Freeman
Keyword(s):  
Present Report ◽  
Three Dimensional ◽  
Surface Shape ◽  
Sharp Change ◽  
Planar Surface ◽  
Lightness Perception ◽  
Starting Point ◽  
Integrated Interpretation ◽  
Shape Data ◽  
Surface Lightness

It is demonstrated that lightness perception can be affected by shape from stereopsis. The starting point was a report by Knill and Kersten that the perceived lightness of a monocularly viewed surface can be affected by outline-contour cues indicating that the surface is three-dimensional (3-D). In that study stimuli consisted of two equally sized abutting regions each having the same vertical linear-intensity ramp, so that the horizontal abutting boundary of the two patches created a sharp change in intensity. When this version of the Craik-O'Brien - Cornsweet stimulus has a rectangular outline, it exhibits the standard simultaneous contrast illusion: equivalent patches in the top and bottom regions appear to have different brightness despite having the same luminance. Knill and Kersten replicated this phenomenon with stimuli whose outline-contour cues were consistent with a flat (planar) surface. They found, however, that the illusion was greatly reduced in stimuli with outlines consistent with two abutting 3-D quarter cylinders, for which equivalent regions in the two halves appeared of similar lightness. Knill and Kersten interpreted this effect in terms of surface-lightness computations that took into account 3-D surface shape to achieve an integrated interpretation of the luminance and shape data. In the present report three experiments are described for which these earlier findings were taken as the starting point. In the first experiment the results were replicated by the use of a different methodology. In the second experiment it was shown that shape-from-stereo can produce similar effects on lightness perception to that caused by shape-from-contour. Real 3-D objects with curved surfaces, luminance profiles of the Knill and Kersten type, and carefully controlled outline-contour cues were used so that the objects appeared flat when viewed monocularly but curved in 3-D when seen binocularly. The third experiment was a control confirming that the stereo effect was not simply due to differences caused by monocular versus binocular viewing. It is concluded that the human visual system uses stereo cues, as well as outline-contour cues, in the interpretation of luminance data to recover surface lightness.

scholarly journals Layered image representations and the computation of surface lightness

2008 ◽  
Vol 8 (7) ◽  
pp. 18 ◽  
Author(s):  
Barton L. Anderson ◽  
Jonathan Winawer
Keyword(s):  
Image Representations ◽  
Surface Lightness
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