Sex-related differences in chromatic sensitivity

Generally women are believed to be more discriminating than men in the use of colour names and this is often taken to imply superior colour vision. However, if both X-chromosome linked colour deficient males (~8%) and females (<1%) as well as heterozygote female carriers (~15%) are excluded from comparisons, then differences between men and women in red-green colour discrimination have been reported as not being significant (e.g., Pickford, 1944; Hood et al., 2006). We re-examined this question by assessing the performance of 150 males and 150 females on the Colour Assessment and Diagnosis (CAD) test (Rodriguez-Carmona, 2005). This is a sensitive test that yields small colour detection thresholds. The test employs direction-specific, moving, chromatic stimuli embedded in a background of random, dynamic, luminance contrast noise. A four-alternative, forced-choice procedure is employed to measure the subject’s thresholds for detection of colour signals in 16 directions in colour space, while ensuring that the subject cannot make use of any residual luminance contrast signals. In addition, we measured the Rayleigh anomaloscope matches in a subgroup of 111 males and 114 females. All the age-matched males (30.8 ± 9.7) and females (26.7 ± 8.8) had normal colour vision as diagnosed by a battery of conventional colour vision tests. Females with known colour deficient relatives were excluded from the study. Comparisons between the male and female groups revealed no significant differences in anomaloscope midpoints (p=0.709), but a significant difference in matching ranges (p=0.040); females on average tended to have a larger mean range (4.11) than males (3.75). Females also had significantly higher CAD thresholds than males along the red-green (p=0.0004), but not along the yellow-blue discrimination axis. The differences between males and females in red-green discrimination may be related to the heterozygosity in X-linked cone photopigment expression common among females

CVD-MET: an image difference metric designed for analysis of color vision deficiency aids

Color vision deficiency (CVD) has gained in relevance in the last decade, with a surge of proposals for aid systems that aim to improve the color discrimination capabilities of CVD subjects. This paper focuses on the proposal of a new metric called CVD-MET, that can evaluate the efficiency and naturalness of these systems through a set of images using a simulation of the subject’s vision. In the simulation, the effect of chromatic adaptation is introduced via CIECAM02, which is relevant for the evaluation of passive aids (color filters). To demonstrate the potential of the CVD-MET, an evaluation of a representative set of passive and active aids is carried out both with conventional image quality metrics and with CVD-MET. The results suggest that the active aids (recoloration algorithms) are in general more efficient and produce more natural images, although the changes that are introduced do not shift the CVD’s perception of the scene towards the normal observer’s perception.Junta de Andalucia A-TIC-050-UGR18Spanish Government FIS2017-89258-PMinisterio de Ciencia, Innovación y Universidades RTI2018-094738-B-I0

Variation of chromatic discrimination across the lifespan

The present study, an extension of Paramei (J. Opt. Soc. Am. A, 29, A290, 2012), provides normative data on chromatic discrimination, using the Cambridge Colour Test, for normal trichromats aged 10–88 years. Findings are in accord with a two-phase variation across the lifespan: chromatic sensitivity improves in adolescence, reaches a maximum around 30 years, and then undergoes a gradual decrease. Indicative parameters are Protan (P), Deutan (D) and Tritan (T) vector lengths; and major axes and axis ratios of Ellipses. Trivector data are modeled as non-monotonic combinations of power functions, with goodness-of-fits R2P=0.23, R2D=0.23, R2T=0.45. For advancing age, sensitivity decline in all chromatic systems was confirmed, though with a marked acceleration after 60 years (reflected by the power function exponent > 1) and more pronounced for the Tritan system

The Effect of Optical Brightening Agent (OBA) in Paper and Illumination Intensity on Perceptibility of Printed Colors

Widely utilized sanctioned color aims for commercial printing are based on paper substrates without optical brightening agents, also known as OBAs. However, in today\u27s market, more and more paper is manufactured with OBAs. This could be problematic for commercial printers as OBAs influence not only paper conformity, but also the accuracy printed colors. This can lead to color mismatch between proofs and the final prints. Recognizing this condition, the objectives of this research were two-fold: first, to verify the perceived color difference between prints due to the presence of OBAs, and second, to study the perceptibility of color differences caused by OBAs in paper substrates, combined with quantitative measurement assessment. In order to satisfy these objectives, the following research questions were investigated: Does CIEDE 2000(∆E00) correlate better with visual scaling or ranking for color differences of printed color pairs than CIELABDE (∆E*ab)? Do different illuminant intensity levels (ISO 3664 P1: 2000lx and P2: 500lx) affect human perceptibility of color differences for color pairs with dark shades? A psychophysical experiment was carried out for evaluating color differences using printed color patches. In total, 27 pairs of printed color patches derived from the IT8.7/4 Target (1,617 color patches) were prepared using the same colorants printed on paper with and without OBA. Each pair was assessed at two levels of illumination by a panel of thirty-four observers. The visual results were used to investigate the relationship between color difference metrics and visual scaling (ranking) of color differences induced by OBAs, as well as the relationship between illumination intensity level and visual scaling of color samples with high-density. The results indicated that: (a) There is better correlation between ∆E00 and the visual scaling of OBA-induced color differences than ∆E*ab; and (b) there is no association between different illumination intensities (i.e., ISO: 3664 P1, P2) and visual scaling of color differences in high-density areas

Abstracts from CIP 2007: Segundo Congreso Ibérico de Percepción

Sin resumenSin resume

Colour Communication Within Different Languages

For computational methods aiming to reproduce colour names that are meaningful to speakers of different languages, the mapping between perceptual and linguistic aspects of colour is a problem of central information processing. This thesis advances the field of computational colour communication within different languages in five main directions. First, we show that web-based experimental methodologies offer considerable advantages in obtaining a large number of colour naming responses in British and American English, Greek, Russian, Thai and Turkish. We continue with the application of machine learning methods to discover criteria in linguistic, behavioural and geometric features of colour names that distinguish classes of colours. We show that primary colour terms do not form a coherent class, whilst achromatic and basic classes do. We then propose and evaluate a computational model trained by human responses in the online experiment to automate the assignment of colour names in different languages across the full three-dimensional colour gamut. Fourth, we determine for the first time the location of colour names within a physiologically-based cone excitation space through an unconstrained colour naming experiment using a calibrated monitor under controlled viewing conditions. We show a good correspondence between online and offline datasets; and confirm the validity of both experimental methodologies for estimating colour naming functions in laboratory and real-world monitor settings. Finally, we present a novel information theoretic measure, called dispensability, for colour categories that predicts a gradual scale of basicness across languages from both web- and laboratory- based unconstrained colour naming datasets. As a result, this thesis contributes experimental and computational methodologies towards the development of multilingual colour communication schemes