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Principles of Color
Published in Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard, Thematic Cartography and Geovisualization, 2022
Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard
The increasing use of color on maps necessitates that mapmakers understand the proper use of color. To assist you in developing this understanding, this chapter covers several issues related to the use of color on maps. In Section 10.3, we consider how either reflected or emitted light from maps passes through the eye and is processed by the eye-brain system. We will see that the processing of color involves two theories. In the trichromatic theory, color perception is a function of the relative stimulation of three types of cones (red, green, and blue) in the retina of the eye. In the opponent-process theory, color perception is based on a lightness–darkness channel and two opponent color channels: red–green and blue–yellow. As a result of these theories, we need to be concerned about simultaneous contrast (that the perceived color of an area can be affected by surrounding colors) and color vision impairment (that approximately 4 percent of the population, primarily males, has some form of color deficiency).
Air Pollution
Published in William J. Rea, Kalpana D. Patel, Air Pollution and the Electromagnetic Phenomena as Incitants, 2018
William J. Rea, Kalpana D. Patel
There are two spectrally opponent cone mechanisms underlying trichromatic human color vision: a blue-vs-yellow channel and a red-vs-green channel. Signals from the three cone photoreceptor types are combined by postreceptor retinal neurons to code color vision. Within the retina, these signals combine in an antagonistic way to form the red-vs-green (L – M) and blue-vs-yellow [S – (L + M)] spectrally opponent channels. These spectrally opponent channels combine with the achromatic channel (primarily L and M) to produce our perceptions of brightness. Because of the spectrally opponent input, the apparent brightness of lights of different spectral power distributions exhibits what is called subadditivity, whereby under certain conditions, adding more light can actually reduce the brightness response of the visual system. Subadditivity by the visual system is demonstrated by comparing the apparent brightness of polychromatic lights to the apparent brightness of each narrow-band spectral component. Under some conditions, the combination of two narrow-band spectra together will appear less bright than either of the two narrow-band spectra alone.23
Perception of Objects in the World
Published in Robert W. Proctor, Van Zandt Trisha, Human Factors in Simple and Complex Systems, 2018
Robert W. Proctor, Van Zandt Trisha
As trichromatic theory predicted, there are three types of cones with distinct photopigments. Color information is coded by the cones in terms of the relative sensitivities of the pigments. For example, a light source of 500 nm will affect all three cone types, with the middle-wavelength cones being affected the most, the short-wavelength cones the least, and the long-wavelength cones an intermediate amount (see Figure 5.11). Because each color is signaled by the relative levels of activity in the three cone systems, any spectral color can be matched with a combination of three primary colors.
Mathematical modelling of sound transmission loss performances of different coloured surfaces coated with polyurethane-based paint
Published in Transactions of the IMF, 2020
H. Ergin Esen, M. Yagimli, H. Tozan, G. E. Yalcin, E. Arca
The Young – Helmholtz’s theory of trichromatic vision, suggests all the colours are created by different ratios of the three main colours in the RGB (red, green, blue) space. The International Commission on Illumination (CIE) in 1931, stipulated that in colour space, there are three main colours containing red, green and blue and the other colours are different concentrations of these three, so that in every colour R (red), G (green), B (blue) colours can be measured.12 LAB values are used in colour universe models based on the human eye. Lab Colour is a global colour model where any given colour can be specified by giving numeric values across different channels. Therefore, the colour of a pigment depends mainly on its LAB values.13
Brightness Model for Neutral Self-Luminous Stimuli and Backgrounds
Published in LEUKOS, 2018
Stijn Hermans, Kevin A. G. Smet, Peter Hanselaer
According to the opponent theory of trichromatic vision, the compressed and adapted cone responses are transformed into three neural signals: the achromatic signal, a weighted combination of all three compressed cone responses, and two color opponent signals (red–green and yellow–blue) containing color information. In this article, only the achromatic signal and brightness are relevant.