Further Evidence of the Effect of Gradient on Lightness

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 63-63 ◽  
Author(s):  
T Agostini ◽  
A Galmonte
Keyword(s):  
Contrast Effect ◽  
Outer Part ◽  
Lightness Contrast ◽  
Simultaneous Comparison ◽  
Black Area

Recently, Agostini and Galmonte (submitted for publication) reported a new effect of gradient on lightness. When two identical mid-gray squares are placed at the centre (white and black, respectively) of two crosses, the first cross having arms filled by a constant achromatic gradient from black (outer part) to white (inner part), and the second cross being the negative of the first one, the gray target surrounded by white appears much darker than that surrounded by black. In a simultaneous comparison, this phenomenon is much stronger than the classical lightness contrast effect. Further observations showed that the effect is quite robust also when the amount of black area is reduced and the gradient is discontinuous. When the gray targets are enlarged to fill the centres of the crosses, the effect is still stronger than that observed in the classical simultaneous lightness contrast display. Furthermore, the effect is independent of the shape of the configuration. The phenomenon can be explained by assuming that the gradient is perceived as a change of the level of illumination rather than as a change of the reflectance of the surfaces.

Effects of Lightness Contrast and Fundus Pigmentation on Age-Related Decrement in Magnitude of the Mueller-Lyer Illusion

1976 ◽  
Vol 42 (3_suppl) ◽  
pp. 1276-1278 ◽  
Author(s):  
Pam Ebert
Keyword(s):  
College Students ◽  
Elementary School ◽  
School Children ◽  
Contrast Effect ◽  
Elementary School Children ◽  
Bimodal Distribution ◽  
Lightness Contrast ◽  
Age Related ◽  
Fundus Pigmentation ◽  
White College

Components of the Mueller-Lyer figure, representing two levels of lightness contrast (1.5 black/ and 7.5 light grey/ each on 9.5 white/ ground) were viewed tachistoscopically for 500 msec. by 65 white elementary school children and 50 white college students. The contrast effect was significant, with black figures yielding a greater illusion than the light grey figures at all age levels. Further, a bimodal distribution of fundus density was evident in both age categories, with more densely pigmented Ss yielding smaller illusions.

Modelling and modification of simultaneous lightness contrast effect using the Albers' pattern

2020 ◽  
Vol 2020 (1) ◽  
pp. 28-32
Author(s):  
Yuechen Zhu ◽  
Ming Ronnier Luo
Keyword(s):  
Contrast Effect ◽  
Colour Vision ◽  
High Accuracy ◽  
Appearance Model ◽  
Visual Data ◽  
Matching Method ◽  
Lightness Contrast ◽  
Normal Colour ◽  
Contrast Pattern ◽  
Colour Appearance

Experiments were carried out to investigate the simultaneous lightness contrast effect on a self-luminous display using simultaneous colour matching method. The Albers ' contrast pattern named ' double-crosses ' was used. The goals of this study were to model lightness contrast effect and modify it in the CAM16 colour appearance model. Five coloured targets were studied, and 41 test/background combinations were displayed on a calibrated display. Twenty normal colour vision observers performed colour matching in the experiment. In total, 820 matches were accumulated. The result shows present CAM16 has an unsatisfactory prediction for the effect, especially in the positive region which means the background is brighter than the target. Two models were established based on the visual data, i. e., with and without modification to the lightness difference in CAM16 space. Both of the models predict the effect with high accuracy and reliability.

The Size Illusion and Lightness Contrast Effect in Delboeuf-like Displays: Possible Evidence of Percept-Percept Coupling

Perception ◽  
10.1068/p7677 ◽  
2014 ◽  
Vol 43 (7) ◽  
pp. 705-710
Author(s):  
Olga Daneyko ◽  
Daniele Zavagno ◽  
Natale Stucchi
Keyword(s):  
Contrast Effect ◽  
Lightness Contrast

Structure of clathrin cages and coats in ice

1986 ◽  
Vol 44 ◽  
pp. 94-97
Author(s):  
G.P.A. Vigers ◽  
R.A. Crowther ◽  
B.M.F. Pearse
Keyword(s):  
Electron Microscopy ◽  
Heavy Chain ◽  
Outer Part ◽  
Coated Vesicles ◽  
Eukaryotic Cells ◽  
Coat Proteins ◽  
Terminal Domain ◽  
Clathrin Heavy Chain ◽  
Membrane Components

Clathrin forms the polyhedral cage of coated vesicles, which mediate the transfer of selected membrane components within eukaryotic cells. Clathrin cages and coated vesicles have been extensively studied by electron microscopy of negatively stained preparations and shadowed specimens. From these studies the gross morphology of the outer part of the polyhedral coat has been established and some features of the packing of clathrin trimers into the coat have also been described. However these previous studies have not revealed any internal details about the position of the terminal domain of the clathrin heavy chain, the location of the 100kd-50kd accessory coat proteins or the interactions of the coat with the enclosed membrane.

Sources of Variability in Dose Response Platelet Aggregometry

1985 ◽  
Vol 53 (02) ◽  
pp. 219-220 ◽  
Author(s):  
M V Vickers ◽  
S G Thompson
Keyword(s):  
Dose Response ◽  
Maximum Velocity ◽  
Adenosine Diphosphate ◽  
Method Error ◽  
Platelet Aggregability ◽  
Differential Effects ◽  
Platelet Aggregometry ◽  
Simultaneous Comparison ◽  
Aggregation Parameters ◽  
Very High

SummaryAn experiment designed to assess the components of variability of a number of measures of platelet aggregability showed that the ADP ED50 (the estimated dose of adenosine diphosphate at which primary aggregation occurs at half its maximum velocity) had the least method error of any of the parameters measured, but that none had a very high between-person component of variability. A simultaneous comparison of a syringe technique and a free-flowing technique for venepuncture revealed no differential effects on the aggregation parameters measured. An enforced increase in the stirring speed in the aggregometer led to an experiment which showed that such a change did not apparently affect the ED50s.

Investigations of past climate and sea-ice variability in the fjord area by Station Nord, eastern North Greenland

1969 ◽  
Vol 35 ◽  
pp. 67-70 ◽  
Author(s):  
Niels Nørgaard-Pedersen ◽  
Sofia Ribeiro ◽  
Naja Mikkelsen ◽  
Audrey Limoges ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
Sea Ice ◽  
Outer Part ◽  
Late Summer ◽  
Field Work ◽  
The Arctic ◽  
Research Station ◽  
Fjord System ◽  
Sea Bottom ◽  
Satellite Radar ◽  
North Greenland

The marine record of the Independence–Danmark fjord system extending out to the Wandel Hav in eastern North Greenland (Fig. 1A) is little known due to the almost perennial sea-ice cover, which makes the region inaccessible for research vessels (Nørgaard-Pedersen et al. 2008), and only a few depth measurements have been conducted in the area. In 2015, the Villum Research Station, a new logistic base for scientific investigations, was opened at Station Nord. In contrast to the early exploration of the region, it is now possible to observe and track the seasonal character and changes of ice in the fjord system and the Arctic Ocean through remote sensing by satellite radar systems. Satellite data going back to the early 1980s show that the outer part of the Independence–Danmark fjord system is characterised by perennial sea ice whereas both the southern part of the fjord system and an area 20–30 km west of Station Nord are partly ice free during late summer (Fig. 1B). Hence, marine-orientated field work can be conducted from the sea ice using snow mobiles, and by drilling through the ice to reach the underlying water and sea bottom.

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