Just Noticeable Difference Model for Images with Color Sensitivity.

The just noticeable difference (JND) model reflects the visibility limitations of the human visual system (HVS), which plays an important role in perceptual image/video processing and is commonly applied to perceptual redundancy removal. However, existing JND models are usually constructed by treating the color components of three channels equally, and their estimation of the masking effect is inadequate. In this paper, we introduce visual saliency and color sensitivity modulation to improve the JND model. Firstly, we comprehensively combined contrast masking, pattern masking, and edge protection to estimate the masking effect. Then, the visual saliency of HVS was taken into account to adaptively modulate the masking effect. Finally, we built color sensitivity modulation according to the perceptual sensitivities of HVS, to adjust the sub-JND thresholds of Y, Cb, and Cr components. Thus, the color-sensitivity-based JND model (CSJND) was constructed. Extensive experiments and subjective tests were conducted to verify the effectiveness of the CSJND model. We found that consistency between the CSJND model and HVS was better than existing state-of-the-art JND models.

Changes in Red Color Sensitivity over the Spawning Cycle of Female Three-spined Stickleback (Gasterosteus aculeatus).

Male red nuptial coloration is a primary mating signal for three-spined sticklebacks (Gasterosteus aculeatus), and the retinae of both sexes are especially sensitive to red during the breeding season. Red sensitivity is an important aspect of female mate choice in this species, but only when they are ready to spawn and not over the entire breeding period. Here, we aimed to determine if the red sensitivity of female sticklebacks change over their repeat spawning cycle. To this end, we assessed retinal opsin mRNA levels and behavioral red sensitivity in females over this cycle. Both methods indicated that females were more sensitive to red during spawning than in the inter-spawning intervals. Relative expression levels of red color opsin genes (lws) and optical motor sensitivity were high during spawning, decreased after the spawning period, and then increased again 72-96 h later when they were ready to spawn again. Thus, female sticklebacks altered their color sensitivity according to need, but the underlying mechanism remains unclear.

Color Sensitivity of the Duration Aftereffect Depends on Sub- and Supra-second Durations.

The perception of duration becomes biased after repetitive duration adaptation; this is known as the duration aftereffect. The duration aftereffect exists in both the sub-second and supra-second ranges. However, it is unknown whether the properties and mechanisms of the adaptation aftereffect differ between sub-second and supra-second durations. In the present study, we addressed this question by investigating the color sensitivity of the duration aftereffect in the sub-second (Experiment 1) and supra-second (Experiment 2) ranges separately. We found that the duration aftereffect in the sub-second range could only partly transfer across different visual colors, whereas the duration aftereffect in the supra-second range could completely transfer across different visual colors. That is, the color-sensitivity of the duration aftereffect in the sub-second duration was stronger than that in the supra-second duration. These results imply that the mechanisms underlying the adaptation aftereffects of the sub-second and supra-second ranges are distinct.

Association between synesthetic colors and sensitivity to physical colors changed by type of synesthetic experience in grapheme-color synesthesia.

Grapheme-color synesthesia is a condition in which visual perception of letters induces simultaneous perception of a specific color. Previous studies indicate that grapheme-color synesthetes are more sensitive to physical colors than non-synesthetes. Synesthetic colors are found to be concentrated in multiple regions of the color space, forming "synesthetic color clusters". The present study investigated whether color sensitivity corresponding to synesthetic color clusters (clustered colors) is higher than color sensitivity that does not correspond to synesthetic color clusters (non-clustered colors). However, we found no difference in the color sensitivity for clustered and non-clustered colors. We also investigated whether the color sensitivity is dependent on the synesthetic experience (associators and projectors). We found that the greater the tendency toward associator characteristics, the greater the sensitivity for clustered colors compared to that for non-clustered colors. Our findings suggest an association between synesthetic colors and physical color sensitivity that is modulated by synesthetic experience.

Color polarization vision mediates the strength of an evolutionary trap.

Evolutionary traps are scenarios in which animals are fooled by rapidly changing conditions into preferring poor-quality resources over those that better improve survival and reproductive success. The maladaptive attraction of aquatic insects to artificial sources of horizontally polarized light (e.g., glass buildings, asphalt roads) has become a first model system by which scientists can investigate the behavioral mechanisms that cause traps to occur. We employ this field-based system to experimentally investigate (a) in which portion(s) of the spectrum are polarizationally water-imitating reflectors attractive to nocturnal terrestrial and aquatics insects, and (b) which modern lamp types result in greater attraction in this typical kind of nocturnal polarized light pollution. We found that most aquatic taxa exhibited preferences for lamps based upon their color spectra, most having lowest preference for lamps emitting blue and red light. Yet, despite previously established preference for higher degrees of polarization of reflected light, most aquatic insect families were attracted to traps based upon their unpolarized spectrum. Chironomid midges, alone, showed a preference for the color of lamplight in both the horizontally polarized and unpolarized spectra indicating only this family has evolved to use light in this color range as a source of information to guide its nocturnal habitat selection. These results demonstrate that the color of artificial lighting can exacerbate or reduce its attractiveness to aquatic insects, but that the strength of attractiveness of nocturnal evolutionary traps, and so their demographic consequences, is primarily driven by unpolarized light pollution. This focuses management attention on limiting broad-spectrum light pollution, as well as its intentional deployment to attract insects back to natural habitats.

Artificial Rod and Cone Photoreceptors with Human-Like Spectral Sensitivities.

Photosensitive materials contain biologically engineered elements and are constructed using delicate techniques, with special attention devoted to efficiency, stability, and biocompatibility. However, to date, no photosensitive material has been developed to replace damaged visual-systems to detect light and transmit the signal to a neuron in the human body. In the current study, artificial nanovesicle-based photosensitive materials are observed to possess the characteristics of photoreceptors similar to the human eye. The materials exhibit considerably effective spectral characteristics according to each pigment. Four photoreceptors originating from the human eye with color-distinguishability are produced in human embryonic kidney (HEK)-293 cells and partially purified in the form of nanovesicles. Under various wavelengths of visible light, electrochemical measurements are performed to analyze the physiological behavior and kinetics of the photoreceptors, with graphene, performing as an electrode, playing an important role in the lipid bilayer deposition and oxygen reduction processes. Four nanovesicles with different photoreceptors, namely, rhodopsin (Rho), short-, medium-, and longwave sensitive opsin 1 (1SW, 1MW, 1LW), show remarkable color-dependent characteristics, consistent with those of natural human retina. With four different light-emitting diodes for functional verification, the photoreceptors embedded in nanovesicles show remarkably specific color sensitivity. This study demonstrates the potential applications of light-activated platforms in biological optoelectronic industries.

Color Perception and Attentional Load in Dynamic, Time-Constrained Environments.

The capacity to perceive color in the peripheral field has attracted research interest for more than a decade. There is evidence that sensitivity to red-green color variations is lower than for yellow-blue in peripheral vision. Whether, and to what extent, color vision affects the visual focus of attention, which is normally much smaller than the visual field, has not yet been examined. We used a sport-specific decision-making task to assess whether the color of the jersey worn by players appearing in the periphery influences decision making by affecting the attentional and perceptual capabilities. Pairs of players wearing chromatic (blue, yellow, red, and green) and achromatic (black, white) colored jerseys were briefly presented across a range of visual angles on a 6 m concave immersive screen. Participants were required to decide to whom to pass and recall relevant information. Findings indicate that color perception changes vary with increasing visual angle, but that the focus of attention is too small to be influenced by jersey color sensitivity. Decision-making performance decreases with increasing visual angle, but is not influenced by color. The implications for decision-making processes in sport and other professional domains are discussed.

Compensation for red-green contrast loss in anomalous trichromats.

For anomalous trichromats, threshold contrasts for color differences captured by the L and M cones and their anomalous analogs are much higher than for normal trichromats. The greater spectral overlap of the cone sensitivities reduces chromatic contrast both at and above threshold. But above threshold, adaptively nonlinear processing might compensate for the chromatically impoverished photoreceptor inputs. Ratios of sensitivity for threshold variations and for color appearance along the two cardinal axes of MacLeod-Boynton chromaticity space were calculated for three groups: normals (N = 15), deuteranomals (N = 9), and protanomals (N = 5). Using a four-alternative forced choice (4AFC) task, threshold sensitivity was measured in four color-directions along the two cardinal axes. For the same participants, we reconstructed perceptual color spaces for the positions of 25 hues using multidimensional scaling (MDS). From the reconstructed color spaces we extracted "color difference ratios," defined as ratios for the size of perceived color differences along the L/(L + M) axis relative to those along the S/(L + M) axis, analogous to "sensitivity ratios" extracted from the 4AFC task. In the 4AFC task, sensitivity ratios were 38% of normal for deuteranomals and 19% of normal for protanomals. Yet, in the MDS results, color difference ratios were 86% of normal for deuteranomals and 67% of normal for protanomals. Thus, the contraction along the L/(L + M) axis shown in the perceptual color spaces of anomalous trichromats is far smaller than predicted by their reduced sensitivity, suggesting that an adaptive adjustment of postreceptoral gain may magnify the cone signals of anomalous trichromats to exploit the range of available postreceptoral neural signals.

Comparison of Color and Contrast Sensitivities Between UVCY(Non-Cyanoptic) and Conventional UV-AB IOLs

The non-cyanoptic, yellow colored posterior chamber intraocular lens (UVCY-IOL, HOYA, Japan) was specially designed to reduce the penetration of ultraviolet (UV) and short wave length visible light(400-500 nm) by adding yellow coloring dye(monomethin) for the pervention of aphakic or pseudophakic cyanopsia, and the obtaining closer color sensitivity and contrast sensitivity to the normal phakic eyes. In this study, we implanted both yellow colored IOLs in 16 eyes and conventional clear UV absorbing IOLs in 12 eyes. They were prospectively followed up for 6 months with questionairs asking subjective symptoms and with contrast s~nsitivity test in order to evaluate the color sensitivity and contrast sensitivity. The subjective symptoms of cyanopsia, photophobia, and glare were signi ficantly reduced in the UVCY-IOL group comparing to the conventional UVAB-IOL group. But in few cases of UVCY-IOL implantation(18.8%) were in episode transiently on xanthopsia with some dim state in early postop periods. The contrast sensitivity pattern of UVCY-IOL group was very similar to that of normal phakic group. The decrement of contrast sensitivity was less in UVCY-IOL group than in conventional UVAB-PCL group. The amount of decreased contrast sensitivity of UVCY-IOL group in scotopic condition was similar to that of conventional UVAB-IOL group. The result of this study suggests that yellow colored IOL is effective in decre asing cyanopsia and photophobia and in improving contrast sensitivity after cataract surgery especially in the early postoperative period. And also we recommend patients would receive UVCY-IOL implantations in both eyes if you have cataract on both eyes.