Human visual system

Thus, one must expect about 5-10% apparently significant correlations fortunately, these false positives appear in a random arrangement, so that when a really significant connection turns up, the human visual system perceives a clearly recognizable pattern, for example for file PROFILE.dat. (See Fig. 4.28.)... 

The primary use of lamplight is to light human activities, and it is high time the lamplight is designed for the human visual system. 

Figure 4. The three-peaked spectral response of the human visual system, the peak...

In summary, lamplight illuminates human activities, so lamp phosphors should feed their light into the human visual system with high visual efficiency. Rare-earth-activated phosphors tend to produce narrow, strongly saturated, brilliantly colored lights. 

Human color perception correlates with integrated reflectance (McCann et al. 1976). Other experiments have shown that the human visual system does not actually estimate the reflectance of objects (Helson 1938). What is known about the visual system is that color processing is done in an area denoted as V4 (visual area no. 4). In V4, cells have been found that respond to different colors irrespective of the type of illuminant (Zeki... 

Instead of performing the homomorphic filtering operation independently on the three color bands, one can transform the image into the coordinate system used by the human visual system and then filter the image in this space. After filtering, the transformation into the coordinate system used by the human visual system can be undone. Note that this method works only if we assume that we have receptors that are similar to delta... 

Figure 7.25 Digital image processing within the framework of what is known about the human visual system (Reproduced by permission of IEEE. Faugeras OD 1979 Digital color image processing within the framework of a human visual model. IEEE Transactions on Acoustics, Speech and Signal Processing, ASSP-27(4) 380-393.)...

So far, we have seen that given a neural architecture, the neural network may be trained to arrive at colors that are approximately constant. Evolution is also able to find a solution to the problem of color constancy. One of the remaining questions is about how a computational color constancy algorithm is actually mapped to the human visual system. Several researchers have looked at this problem and have proposed possible solutions. 

Figure 14.2 Likely description of the color constancy algorithm used by the human visual system to compute color constant descriptors. The parameter p is simply a small percentage as described in Section 10.2.

A summary of symbols and units that are used in radiometry is shown in Table B.l. A summary of symbols and units that are used in photometry is shown in Table B.2. The photometric quantities use the same symbol except that the subscript v is added. A good introduction to the theory of radiometry is given by Poynton (2003), Jahne (2002), Horn (1986), and Levi (1993). See also International Commission on Illumination (1983). The radiometric units refer to physical quantities whereas the photometric units refer to perceptual quantities. In photometry, the physical quantities are weighted by the spectral sensitivity of the human visual system. Let Q(X) be the energy at wavelength X. Then, the corresponding photometric quantity is given by... 

To support vision throughout the animal kingdom, including in chordates, it is necessary for the genetic code to support the formation of four distinct forms of Rhodonine. These forms are the four distinct narrowband chromophores, Rhodonine(5) for the L-channel, Rhodonine(7) for the M-channel, Rhodonine(9) for the S-channel and Rhodonine(l 1) for the UV-channel. All four of these chromophores and channels are employed in the human visual system. The performance of the UV-channel is only restricted by the transmission properties of the physiological lens. 

As an example we mention the sensitivity at low light intensities of the human visual system which according to a careful analysis by Rose (1) is close to the theoretical limit. The system thus can be considered as an image converter of the highest possible sensitivity, though it uses materials of quite a different nature from those used by technologists. 

Grose-Fifer J, Zemon V, Gordon J. 1994. Temporal tuning and the development of lateral interactions in the human visual system. Invest Ophthalmol Vis Sci 35 2999-3010. 

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