Contrast adaptation
Pablo Artal in Handbook of Visual Optics, 2017
Even longer-lasting effects were observed by Delahunt et al. (2004) in the changes in color perception. It is well known that, during aging, the crystalline lens becomes yellowish, with declining transmission in the short wavelength range. Figure 21.32a illustrates how an image should look like through an aging lens. However, even though much less energy is then in the retinal image in the short wavelength range, subjects are not aware of this loss due to their long-term color adaptation. If the lens is replaced by a plastic intraocular lens during cataract extraction, transmission in the blue is recovered and spectral sensitivity of the subjects in the short wavelengths range is much enhanced (Figure 21.32b). Measuring the achromatic locus in those subjects in the CIE diagram (Figure 21.32d) shows that the recovery to “normal” (with a clear lens) takes many days (Figure 21.32c).
Spectral Imaging Technologies and Apps and Dual-Layer Detector Solution
Katsuyuki Taguchi, Ira Blevis, Krzysztof Iniewski in Spectral, Photon Counting Computed Tomography, 2020
Following the principle of natural selection, two kinds of photoreceptor cell evolved with different energy response. While these new types of photoreceptor cells still maintain the basic mechanism of response that is dependent on the total amount of absorbed energy, each type exhibits a different spectral sensitivity, i.e., different detection efficiencies for the same light spectrum. That is, not to say that there is a complete energy separation between the two spectral responses, but that, despite the partial overlap between the two response spectra, a different detection signal is produced by each type of photoreceptor cell. This new scheme allowed for the differentiation between objects or surfaces that presented little or no signal difference in the one-dimensional scheme and provided an evolutionary advantage in various situations. The interpretation of the signals by the brain is now referred to as color vision, which combines information of both the integrated energy and the wavelength contrasts to detect objects for signals from cells, or channels, in the same areas of visual space. When the integrated energy contrast between different objects is absent or insufficient, “wavelength contrast” [1] may still be available to differentiate between them – it may be that two objects reflect the same amount of energy; however, it is unlikely that they reflect the same wavelength composition.
Color Correspondences in Chemosensation
Alan R. Hirsch in Nutrition and Sensation, 2023
Before we go any further, it is important to introduce some basic concepts from the field of color perception research. Color is defined as a perceptual response to the visible spectrum of light (the distribution of light power as a function of the wavelength) reflected or emitted by the surface of an object. This signal interacts in the eye with the L, M, and S cones in the retina, these names referring to the long-, middle-, and short-wavelength sensitive cones, respectively. These signals are then ultimately transmitted to the visual cortex by the optic nerve (Zeki 1993). Eventually, the human observer assigns a color to this signal. Such arguments have led some researchers to suggest that color is not an intrinsic property of the surface of an object, since if the light source changes, so too does the color of its surface (Melendez-Martinez, Vicario, and Heredia 2005; Shepherd 2012). The perception of color, then, is a complex phenomenon that depends on the properties of an object in a given illumination environment, the characteristics of the perceiving eye and brain, and the angle of illumination and viewing.
Effect of Background Luminance Level on the Assessment of Color Visual Acuity Using Colored Landolt Rings in Young Healthy Subjects
Published in Current Eye Research, 2018
Yoshiki Tanaka, Sho Yokoyama, Rie Horai, Takashi Kojima, Sato Hiroyuki, Yukihito Kato, Mari Takagi, Hideki Nakamura, Kiyoshi Tanaka, Kazuo Ichikawa, Shoko Tanabe
Human visual perception consists of spatial characteristics, temporal characteristics, and color vision. We believe that combining a color vision test with other visual function tests could be helpful for evaluating the quality of vision in daily life. The acquired color vision deficiencies may occur secondarily to a disease and its symptoms varies with characteristic of aggravation and remission. Measuring CVA may be helpful for confirming a diagnosis in some ocular disorders. Therefore, we developed a novel testing system that can examine human visual performance of different colors using a personal computer (PC) and a liquid crystal display (LCD) monitor. We adopted Landolt rings from conventional visual acuity charts as the stimulus to present to the subjects. We defined the visual acuity for each color as “color visual acuity” (CVA). Using our CVA testing system, the colors of the stimulus and background were arbitrarily set using a specific hardware exhibiting accurate color reproducibility.
Being Treated as an Instrument: Consequences of Instrumental Treatment and Self-Objectification on Task Engagement and Performance
Published in Human Performance, 2021
Cristina Baldissarri, Luca Andrighetto
The participants were individually examined under the supervision of an experimenter, who was also the confederate for both experimental conditions (instrumental vs. non-instrumental). The study was introduced as research on color perception. In both conditions, the participants were initially welcomed by the experimenter in a similar neutral manner and signed the informed consent. Then, depending on the condition, the experimenter treated the participants in an instrumental vs. non-instrumental way through a specific script described below. Afterward, participants’ performance was assessed through a cognitive task and their level of self-objectification and task engagement through self-report measures. At the end of the session, the participants were fully debriefed and thanked.
Identification of colorblindness among selected primary school children in Hararghe Region, Eastern Ethiopia
Published in Alexandria Journal of Medicine, 2018
Temesgen Tola Geletu, Manikandan Muthuswamy, Tamiru Oljira Raga
Color vision deficiency is one of widely investigated genetic marker in the study of human variation and it is an essential genetic trait in the area of human genetics. It has been pointed out that natural selection functions more intensively on colorblindness among many primitive populations of the world.9 In a normal individual or trichromat, three wavelengths are required to match wavelength of a light. Abnormal (red-green) or dichromacy occurs when there are only two cones operate in distinguishing the wavelength of a light. More severe type of color vision defects, monochromacy and achromacy only has a single wavelength to match the reference color.10
Related Knowledge Centers
- Eye
- Photoreceptor Cell
- Visual Perception
- Visual System
- Ultraviolet
- Brain
- Evolution of Color Vision
- Visible Spectrum
- Just-Noticeable Difference
- Scotopic Vision