Measurement of the effect of chromaticity and intensity on colour representation parameters of a CRT display

The aim of the measurement detailed in this paper was to measure the just-noticable stimuli of the participating subjects. The stimuli were defined by chromaticity and intensity as the main parameters of the mathematical model. The results show correlance between intensity and the just-noticable stimuli, as described in the Weber-Frechner Law but a contradiction was shown after the analysis in the function of chromaticity. This contradiction can be explained by the difference between the sensitivity of the three cones of the eye

Perspective with Six Vanishing Points - an Alternative Method

The purpose of this paper is to describe perspective with six vanishing points. The line opened by axonometry and continued by one, two, three vanishing points and spherical perspectives, one became complete with the sixth vanishing point. Linear perspectives are often used, well known systems. Introducing new vanishing points doubles the represented part of space. The question of representing the half-space, hence the definition of the first five vanishing points can be found in literature. However, there was no useful solution for the representation of the whole space for a long time. This paper introduces a new definition of the sixth vanishing point that resulted a well applicable system. A short historical introduction looks at some of the interactions between mathematics and arts of western culture. Afterwards we formulate the new alternative perspective and give some methods of construction for notable lines and planes. Finally we write about possible applications

Chromatic Discrimination Thresholds as a Function of Color Differences and Cone Excitations

In this paper, Just Noticeable Differences (JNDs) of color-normal subjects measured towards the Protan, Deutan, and Tritan confusion points are presented as a function of the chromaticity of the reference points. Measurements were executed with the Cambridge Colour Test Trivector test in equidistant reference points towards eight directions equally spaced and centered on the neutral reference point in the CIE 1976 UCS diagram.Results were evaluated as the function of the distance between the reference points and the neutral point. The reference points were the chromaticities of the backgrounds of the pseudoisochromatic plates in the test, and the neutral point was defined as equal energy white. The evaluation was performed considering ∆Eu'v' differences and L/(L + M) and S/(L + M) ratios of the cone-excitations.Chromatic discrimination thresholds exceeded the normative upper limit of color normal subjects in ∆Eu'v' units at extreme reference points. Shifting the reference points from the neutral point towards the confusion points indicated an increase of Just Noticeable Differences measured towards the confusion points following second-order polynomials. Based on our results a model estimating the JNDs expressed in ∆Eu'v' units towards the confusion points was recommended.Even though CIE 1976 UCS diagram is not a perceptually uniform color space, the Just Noticeable Differences measured with the CCT correlate with the corresponding L' and S' cone excitations. This confirms the basic applicability of the CIE 1976 UCS diagram for characterizing Just Noticeable Differences. For complete perceptual analysis, the use of cone-excitation-based metrics is still essential and recommended

The Effect of the Field of Adaptation on Chromatic Discrimination Ellipses

In this paper results of chromatic discrimination measurements obtained in two lighting scenarios are compared. Chromatic discrimination thresholds were measured in relation with systematically manipulated chromaticities seen under different visual angles. In both cases the Ellipse module of the Cambridge Colour Test (CCT) was obtained binocularly by normal colour-observers. Discrimination ellipses fitted to the measured thresholds were compared in terms of the adapting chromaticity and the visual angle of the adapting stimulus. Our findings show that changes in the reference chromaticity of the CCT have stronger effect on the elongation of the chromatic discrimination ellipses compared to the effect of the adapting chromaticity obtained in a light booth.Further comparison of discrimination thresholds estimated towards the confusion directions and the corresponding radii of the Ellipse test results suggests that the reliability of the Ellipse test results depends on the relation between the measurement directions and the confusion directions

Színdiszkrimináció a konfúziós irányok mentén

A publikációban bemutatott kutatás során épszínlátó személyek színdiszkriminációs küszöbértékei kerültek összehasonlításra. A küszöbértékek a Cambridge Colour Test Ellipszis és Trivector moduljaival kerültek meghatározásra, különböző referenciapontokhoz képest. Az eredmények különbséget mutatnak a referenciapontok elhelyezkedésének függvényében. A konfúziós irányokban mért küszöbértékek esetén egy CRT-monitor gamutján belül találhatóak olyan referenciapontok, amelyek körül épszínlátó személyek eredményei is meghaladhatják az épszínlátó személyek küszöbértékeinek felső határértékét. A konfúziós irányok mentén, Trivector mérések alapján becsült küszöbértékek meghaladták az ellipszistesztek által a konfúziós irányokban meghatározott küszöbértékeket. Az eredményeink alapján színdiszkriminációs ellipszisek meghatározásakor javasolt a konfúziós irányok mentén is méréseket végezni

Non linear space representation -perspective with six vanishing-points

Abstract The objective of this paper is to give an overview of the main principles of space representation in perspective with six vanishing points. The system built up from perspectives based on the number of the vanishing points is finished with the sixth one, in case that the vanishing points are both ideal points of each of the 3 axes of a cartesian coordinate system. Thereby besides the origin of the above mentioned cartesian coordinate system, the whole space can be represented on one image. Processing and displaying the data of a scene helps to learn visualising the world in the new system compared to the traditional perspectives, and also shows further directions for technical development

Vision tests of sensory judges - review

In sensory examinations, judges must be in good general health. They should not have any deficiencies that could affect their perception or adversely affect their sensory performance, and thus can affect the reliability of their judgments. The vision of a judge is basically determined by three factors: visual acuity, contrast sensitivity and color vision. In the international practice of sensory analyses, color vision is generally examined. Color blindness is typically tested using the Ishihara pseudo-isochromatic color test, while color discrimination ability is examined using the Farnsworth-Munsell 100 hue test [1]. The most accurate tool to detect color blind people is the anomaloscope. Screening for color blind people is important because they have both poorer color discrimination abilities and poorer color identification abilities. The results of online color vision tests are significantly affected by the display device and its settings (monitor resolution, color-correct calibration), as well as test conditions: test geometry (relative position of the light source, the test book and the eye), photometric and spectral nature of the light source and the monitor, and the adaptation state of the eye. Unfortunately, the specifications for standard sensory tests do not require the visual acuity and contrast sensitivity testing of sensory judges, however, these properties obviously affect visual perception, so testing them is necessary

Organoleptic validation of a color masking system specified for green and black tea (Camellia sinensis L.) brews

Numerous studies focusing on organoleptic tests have shown that the visual characteristics of the product under study cause a preconception (expectation error) in the judge, which distorts the perception of the other sensory characteristics to varying degrees. In cases where the rating is not based on visual judgment, it is advisable to ensure test conditions where it can be ruled out that the color stimulus of the product does not influence the decision of the judges [1]. Consequently, it is necessary to reduce the intensity of color sensation or the quality of the sensation, but most of all to mask them. The methods widely used in practice (blindfolding, colored vessels, colored lenses, etc.) are subject to distortions, therefore, a spectrally adjustable lighting system specified for the types of the given product can provide a solution to eliminate these by optimizing the parameters of the observation and by the sensory validation of them. The said spectrally adjustable LED measuring system with a homogeneous light distribution is controlled by arduino (an open-source electronic prototyping platform enabling users to create interactive electronic objects - ed.). In our study, the organoleptic validation of a color masking system specified for green and black tea (Camellia sinensis L.) brews is presented. Participants of the experiment were tested according to international standards [2, 3]; based on our test results, they had normal vision in all respects. The results showed that, by color masking the smallest detectable threshold value and by determining the spectral characteristics, differences in visual perception between sample pairs with a certain difference in color stimulus can be partially or completely masked. As a result, under perfectly masking illumination, expectation errors due to perception do not distort the judgment of the other organoleptic characteristics (such as smell, taste, texture and mouth coating) of tea brews. Partial masking eliminates color differences in many cases, increases judgment time 4 to 8-fold, however, differences due to brightness remain observable