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Vision Ranges Linked to Qur-an and Hadith

Hussain Omari

Physics Dept./ Mutah University/ Jordan

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ɡ : ( ) . (Vision Range) .

(Narrated Abu Huraira: The Prophet said, "When you hear the crowing of cocks, ask for Allah's Blessings for (their crowing indicates that) they have seen an angel. And when you hear the braying of a donkey, seek Refuge with Allah from Satan for (its braying indicates) that it has seen a Satan." ). This hadith refers to the scientific fact that Vision Ranges differ for different creatures.

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[27] O ye Children of Adam! let not Satan seduce you, in the same manner as he got your parents out of the Garden, stripping them of their raiment, to expose their shame: for he and his tribe watch you from a position where ye cannot see them: We made the Evil Ones friends (only) to those without Faith.

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( * * ) ( 69 : 38-40)

(So I do call to witness what ye see * And what ye see not * That this is verily the word of an honoured Messenger) (S. 69, V. 38-40)

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Part 2:

Some animals see differently than we do. Some animals, like bees, have cones for colors we can't see. Some animals have developed a highly-advanced senses of smell or specialized hearing abilities such as echolocation. Others have acquired eye adaptations for improved night vision.

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Big Eyes

The most interesting feature of nocturnal animals ( ) is the size of their eyes. Large eyes, with a wider pupil, larger lens and increased retinal surface collect more light. Some animal species have evolved tubular eyes as a means of increasing their size. Many nocturnal animals cannot move their eyes within the orbit. Instead, they have evolved extraordinary rotational ability in the neck. Owls, for example, can rotate their neck through 270 & this aids their vision.

Some animals of the night have acquired a spherical lens and widened cornea to compensate for reduced eye movement. This combined with a wide cornea increases the animals field of view allowing the head and eyes to remain motionless.

Mirrors Add Intensity, Eyes glow in the dark

On a dark night, flash a bright light at your dog or cat's eyes & you notice that their eyes glow in the dark. It is the tapetum lucidum (meaning "bright carpet"), an adaptation for night vision. The tapetum is a thick reflective membrane, 15 cells wide, directly beneath the retina. It collects and re-emits light back to the retina a second time, giving the rods a second chance to absorb the image information, thus maximizing the little light available to them. As this light is reflected off the tapetum, the animal's eyes appear to glow.

Although nocturnal animals see mostly crude or imperfect shapes, outlines and no colors, by maximizing their sensitivity to low light levels with the above adaptations, it is enough for them to hunt, feed and survive in the dark of night.

In The Daylight

Most nocturnal animals are often inactive during the day to avoid over-stimulating their highly sensitive eyes. Nocturnal animals have specialized pupils to shut out damaging bright day light. Nocturnal animals dilate their pupils to their circular maximum at night.

Electromagnetic waves exist with an enormous range of frequencies. This continuous range of frequencies is known as the electromagnetic spectrum. The entire range of the spectrum is often broken into specific regions. The subdividing of the entire spectrum into smaller spectra is done mostly on the basis of how each region of electromagnetic waves interacts with matter. The diagram below depicts the electromagnetic spectrum and its various regions. The longer wavelength (), lower frequency (f) regions are located on the far left of the spectrum and the shorter wavelength (), higher frequency (f) regions are on the far right. Two very narrow regions within the spectrum are the visible light region and the X-ray region.

Visible spectrum (From Wikipedia, the free encyclopedia)

White light dispersed by a prism into the colors of the optical spectrum.

The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm.[1] In terms of frequency, this corresponds to a band in the vicinity of 790400 terahertz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum (see: luminosity function). The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can only be made by a mix of multiple wavelengths.

Visible wavelengths also pass through the "optical window", the region of the electromagnetic spectrum that passes largely unattenuated through the Earth's atmosphere. Clean air scatters blue light more than wavelengths toward the red, which is why the mid-day sky appears blue. The human eye's response is defined by subjective testing (see CIE), but atmospheric windows are defined by physical measurement.

The "visible window" is so called because it overlaps the human visible response spectrum. The near infrared (NIR) windows lie just out of human response window, and the Medium Wavelength IR (MWIR) and Long Wavelength or Far Infrared (LWIR or FIR) are far beyond the human response region.

Many species can see wavelengths that fall outside the "visible spectrum". Bees and many other insects can see light in the ultraviolet, which helps them find nectar in flowers. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light, rather than how colorful they appear to us. Birds too can see into the ultraviolet (300400 nm), and some have sex-dependent markings on their plumage, which are only visible in the ultraviolet range.[2][3]

History

Newton's color circle, from Opticks of 1704, showing the colors correlated with musical notes. The spectral colors from red to violet are divided by the notes of the musical scale, starting at D. The circle completes a full octave, from D to D. Newton's circle places red, at one end of the spectrum, next to violet, at the other. This reflects the fact that non-spectral purple colors are observed when red and violet light are mixed.

Two of the earliest explanations of the optical spectrum came from Isaac Newton, when he wrote his Opticks, and from Goethe, in his Theory of Colours, although earlier observations had been made by Roger Bacon who first recognized the visible spectrum in a glass of water, four centuries before Newton discovered that prisms could disassemble and reassemble white light.[4]

Newton first used the word spectrum (Latin for "appearance" or "apparition") in print in 1671 in describing his experiments in optics. The word "spectrum" [Spektrum] was strictly used to designate a ghostly optical afterimage by Goethe in his Theory of Colors and Schopenhauer in On Vision and Colors. Newton observed that when a narrow beam of sunlight strikes the face of a glass prism at an angle, some is reflected and some of the beam passes into and through the glass, emerging as different colored bands. Newton hypothesized that light was made up of "corpuscles" (particles) of different colors, and that the different colors of light moved at different speeds in transparent matter, with red light moving more quickly in glass than violet. The result is that red light bends (refracted) less sharply than violet as it passes through the prism, creating a spectrum of colors.

Newton divided the spectrum into seven named colors: red, orange, yellow, green, blue, indigo, and violet. (Some schoolchildren memorize this order using the mnemonic ROY G. BIV.) He chose seven colors out of a belief, derived from the ancient Greek sophists, that there was a connection between the colors, the musical notes, the known objects in the solar system, and the days of the week.[5][6] The human eye is relatively insensitive to indigo's frequencies, and some otherwise well-sighted people cannot distinguish indigo from blue and violet. For this reason some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right but merely as a shade of blue or violet.

Johann Wolfgang von Goethe argued that the continuous spectrum was a compound phenomenon. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum, but rather reddish-yellow and blue-cyan edges with white between them. The spectrum only appears when these edges are close enough to overlap.

In the early 19th century, the concept of the visible spectrum became more definite, as light outside the visible rangeultraviolet and infraredwas discovered and characterized by William Herschel, Johann Wilhelm Ritter, Thomas Young, Thomas Johann Seebeck, and others.[7] Young was the first to measure the wavelengths of different colors of light, in 1802.[8]

The connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century. Their theory of color vision correctly proposed that the eye uses three distinct receptors to perceive color.

Spectral colors

Color

Wavelength

Frequency

violet

380450 nm

668789 THz

blue

450495 nm

606668 THz

green

495570 nm

526606 THz

yellow

570590 nm

508526 THz

orange

590620 nm

484508 THz

red

620750 nm

400484 THz

Colors that can be produced by visible light of a single wavelength (monochromatic light) are referred to as the pure spectral colors.

File:Linear visible spectrum.svg

Linear_visible_spectrum.svg (SVG file, nominally 605 115 pixels, file size: 13 KB)

(http://upload.wikimedia.org/wikipedia/commons/d/d9/Linear_visible_spectrum.svg)

Although the spectrum is continuous, with no clear boundaries between one color and the next, the ranges may be used as an approximation.[9]

Spectroscopy

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

Spectroscopy is the study of objects based on the spectrum of color they emit or absorb. Spectroscopy is an important investigative tool in astronomy where scientists use it to analyze the properties of distant objects. Typically, astronomical spectroscopy uses high-dispersion diffraction gratings to observe spectra at very high spectral resolutions. Helium was first detected by analyzing the spectrum of the Sun. Chemical elements can be detected in astronomical objects by emission lines and absorption lines. The shifting of spectral lines can be used to measure the red shift or blue shift of distant or fast-moving objects. The first exoplanets were discovered by analyzing the Doppler shift of stars at a resolution that revealed variations in radial velocity as small as a few meters per second. The presence of planets was revealed by their gravitational influence on the motion of the stars.
Color display spectrum

Color spectrum generated in a display device.

Color displays (e.g., computer monitors and televisions) mix red, green, and blue color to create colors within their respective color triangles, and so can only approximately represent spectral colors, which are in general outside any color triangle.

File:Spectrum (brown background).png

No higher resolution available. Spectrum_(brown_background).png (575 120 pixels, file size: 3 KB, MIME type: image/png)

(http://en.wikipedia.org/wiki/File:Rendered_Spectrum.png)

A render of the color spectrum into the sRGB color space on a brown background.

Colors outside the color gamut of the display device result in negative values. If color accurate reproduction of the spectrum is desired, negative values can be avoided by rendering the spectra on a gray background. This gives an accurate simulation of looking at a spectrum on a gray background.[10]
Scanning

The world of desktop scanners has crossed the threshold of Deep Color where scanners are capable of capturing a billion or more colors.

Part 3:

Flicker Sensitivity of the Chicken

Ref.:

Flicker:. , ,

 

Figures

See also

Definition of Contrast: Contrast is the difference in similarity and comparison to others. It is emphasizing differences and showing distinctions as in light versus darkness.

Figure - The contrast sensitivity function describes how poor the contrast can become and still be perceptible. As the contrast sensitivity value rises, the lower the contrast becomes. Combining the experimental data with data for cats, pigeons, and humans, the hooded rat has comparatively poor eyesight that may still be useful for medical studies (Ref.: Vision in the Animal Kingdom: Vision in the Animal Kingdom (Kenneth Kang, Psychology 221 - Applied Vision and Image Systems, Stanford University - Winter 2002).

In terms of the diversity of eyes and vision, birds are quite amazing. While birds have a structure within their eye called a pecten whose purpose is not clear, they are capable of seeing ultraviolet and polarized light with about four classes of cones. Their cone cells have oil droplets to help distinguish colors. Moreover, they have a higher flicker-fusion frequency, 100 Hz compared to 60 Hz for humans (Ref.: Vision in the Animal Kingdom).

Ref.: ()

References

1.                 ^ Cecie Starr (2005). Biology: Concepts and Applications. Thomson Brooks/Cole. ISBN 053446226X. http://books.google.com/books?id=RtSpGV_Pl_0C&pg=PA94. 

2.                 ^ Cuthill, Innes C; et al. (1997). "Ultraviolet vision in birds". in Peter J.B. Slater. Advances in the Study of Behavior. 29. Oxford, England: Academic Press. p. 161. ISBN 978-0-12-004529-7. 

3.                 ^ Jamieson, Barrie G. M. (2007). Reproductive Biology and Phylogeny of Birds. Charlottesville VA: University of Virginia. p. 128. ISBN 1578083869. 

4.                 ^ Coffey, Peter (1912). The Science of Logic: An Inquiry Into the Principles of Accurate Thought. Longmans. http://books.google.com/books?id=j8BCAAAAIAAJ&pg=PA185&dq=%22roger+bacon%22+prism&ei=TX8OSJ2jMZCSzQTKx8y7Ag&client=firefox-a. 

5.                 ^ Hutchison, Niels (2004). "Music For Measure: On the 300th Anniversary of Newton's Opticks". Colour Music. http://home.vicnet.net.au/~colmusic/opticks3.htm. Retrieved 2006-08-11. 

6.                 ^ Newton, Isaac (1704). Opticks. 

7.                 ^ Mary Jo Nye (editor) (2003). The Cambridge History of Science: The Modern Physical and Mathematical Sciences. 5. Cambridge University Press. p. 278. ISBN 9780521571999. http://books.google.com/books?id=B3WvWhJTTX8C&pg=PA278&dq=spectrum+%22thomas+young%22+herschel+ritter&lr=&as_brr=0&as_pt=ALLTYPES&ei=XZT2Se_dF4vOkwT9tMigBA. 

8.                 ^ John C. D. Brand (1995). Lines of light: the sources of dispersive spectroscopy, 1800-1930. CRC Press. p. 3032. ISBN 9782884491631. http://books.google.com/books?id=sKx0IBC22p4C&pg=PA30&dq=light+wavelength+color++young+fresnel&as_brr=3&ei=zpX2SdWLIpDmkASaxq3LBA#PPA31,M1. 

9.                 ^ Thomas J. Bruno, Paris D. N. Svoronos. CRC Handbook of Fundamental Spectroscopic Correlation Charts. CRC Press, 2005.

10.            ^ http://www.repairfaq.org/sam/repspec/

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S45.4: UV vision and its functions in birds

Innes C. Cuthill, Julian C. Partridge & Andrew T. D. Bennett

School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK, fax 44 117 925 7374, e-mail I.Cuthill@bris.ac.uk; J.C.Partridge@bris.ac.uk; Andy.Bennett@bris.ac.uk

Cuthill, I.C., Partridge, J.C. & Bennett, A.T.D. 1999. UV vision and its functions in birds. In: Adams, N.J. & Slotow, R.H. (eds) Proc. 22 Int. Ornithol. Congr., Durban: 2743-2758. Johannesburg: BirdLife South Africa.

Birds can see ultraviolet (UV) light because, unlike humans, their lens, cornea and other ocular media transmit UV, and they possess a retinal cone type which is maximally sensitive to violet or ultraviolet light, depending on the species. As birds also have cones sensitive to blue, green and red light, they may have a tetrachromatic colour vision system.

Full article: http://www.int-ornith-union.org/files/proceedings/durban/Symposium/S45/S45.4.htm

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Ultraviolet (UV) light perception by birds: a review, J. Rajchard Faculty of Agriculture, University of South Bohemia, Ceske Budejovice, Czech Republic. Veterinarni Medicina, 54, 2009 (8): 351359: (http://www.vri.cz/docs/vetmed/54-8-351.pdf)

The ability to perceive (observe) the near ultraviolet part of the light spectrum (the wavelength 320400 nm) has been detected in many bird species.

It is now known that avian ocular media do not absorb UV light before it reaches the retina; thus UV sensitivity in birds is possible. Birds have 45 types of single cone photoreceptors, including one type sensitive to UV light (for comparison humans have only three types of cone photoreceptors). Many birds (obviously the majority of species, e.g., many non-passerines) have a violet-sensitive single cone that is obviously sensitive to UV wavelengths. Other species (e.g., some passerines) have a single cone that has maximum sensitivity to UV light.

The spectral sensitivity of domestic ducks (Anas platyrhynchos domesticus) and turkeys (Meleagris gallopavo gallopavo) was tested over a range of specified wavelengths, including UVA, between 326694 nm in comparison with human spectral sensitivity (Barber et al., 2006). The results showed that ducks and turkeys had similar spectral sensitivities and could perceive UVA radiation. Turkeys were more sensitive to UVA than ducks. The peak sensitivity was in the wavelengths between 544577 nm, with reduced sensitivity at 508600 nm. Both bird species had a very different and broader range of spectral sensitivity than humans.

 

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information. http://hsc.csu.edu.au/biology/options/communication/2950/CommPart2.html

Type of animal

Name of animal

Part of electromagnetic spectrum detected

Wavelengths detected

Vertebrate

Human

visible

700-400 nm

 

Rattlesnake

infra-red and visible

850-480 nm

 

Japanese dace fish

ultraviolet and visible

as low as 360 nm

Invertebrate

Honeybee

ultraviolet and visible

700-300 nm

 

Mantis shrimp

ultraviolet and visible

640-400 nm

 

Table:

(http://anthonymbiotask3.wikispaces.com/Light+and+the+electromagnetic+spectrum) or

http://hsc.csu.edu.au/biology/options/communication/2950/CommPart2.html

Type of animal

Name of animal

Electromagnetic spectrum used

Reasons

Vertebrate

Human

visible

Active during the day uses colour for perception of objects

 

Rattlesnake

infra-red and visible

Active at night hunts in dark burrows

 

Hummingbird

visible

Can detect flowers from over a kilometre away

Invertebrate

Honeybee

ultraviolet and visible

Can detect ultraviolet markings on flowers and uses polarised light for navigation

 

Mantis shrimp

ultraviolet and visible

Can perceive many more colours and escape predation in the well lit waters were it lives

 

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Part 4: Color vision:

From Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Color_vision)

Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit. The nervous system derives color by comparing the responses to light from the several types of cone photoreceptors in the eye. These cone photoreceptors are sensitive to different portions of the visible spectrum. For humans, the visible spectrum ranges approximately from 380 to 740 nm, and there are normally three types of cones. The visible range and number of cone types differ between species.

A 'red' apple does not emit red light.[1] Rather, it simply absorbs all the frequencies of visible light shining on it except for a group of frequencies that is perceived as red, which are reflected. An apple is perceived to be red only because the human eye can distinguish between different wavelengths. The advantage of color, which is a quality constructed by the visual brain and not a property of objects as such, is the better discrimination of surfaces allowed by this aspect of visual processing. In some dichromatic substances (e.g. pumpkin seed oil) the color hue depends not only on the spectral properties of the substance, but also on its concentration and the depth or thickness[2].

Wavelength and hue detection

Isaac Newton discovered that white light splits into its component colors when passed through a prism, but that if those bands of colored light pass through another and rejoin, they make a white beam. The characteristic colors are, from low to high frequency: red, orange, yellow, green, cyan, blue, violet. Sufficient differences in frequency give rise to a difference in perceived hue (hue: is the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, blue, and yellow); the just noticeable difference in wavelength varies from about 1 nm in the blue-green and yellow wavelengths, to 10 nm and more in the red and blue. Though the eye can distinguish up to a few hundred hues, when those pure spectral colors are mixed together or diluted with white light, the number of distinguishable chromaticities can be quite high.

In very low light levels, vision is scotopic, meaning mediated by rod cells, and not detecting color differences; the rods are maximally sensitive to wavelengths near 500 nm. In brighter light, such as daylight, vision is photopic, in which case the cone cells of the retina mediate color perception, and the rods are essentially saturated; in this region, the eye is most sensitive to wavelengths near 555 nm. Between these regions is known as mesopic vision, in which case both rods and cones are providing meaningful signal to the retinal ganglion cells. The shift in color perception across these light levels gives rise to differences known as the Purkinje effect.

The perception of "white" is formed by the entire spectrum of visible light, or by mixing colors of just a few wavelengths, such as red, green, and blue, or even by mixing just a pair of complementary colors such as blue and yellow.[3]

Physiology of color perception

Normalized response spectra of human cones, short (S), medium (M), and long (L) types, to monochromatic spectral stimuli, with wavelength given in nanometers.

The same figures as above represented here as a single curve in three (normalized cone response) dimensions

Single color sensitivity diagram of the human eye.

Perception of color is achieved in mammals through color receptors containing pigments with different spectral sensitivities. In most primates closely related to humans there are three types of color receptors (known as cone cells). This confers trichromatic color vision, so these primates, like humans, are known as trichromats. Many other primates and other mammals are dichromats, and many mammals have little or no color vision. Indeed, "mammals with color vision are rare," with most mammals having rod-dominated retinas, and some having pure-rod ones.[4]

The cones are conventionally labeled according to the ordering of the wavelengths of the peaks of their spectral sensitivities: short (S), medium (M), and long (L) cone types, also sometimes referred to as blue, green, and red cones. While the L cones are often referred to as the red receptors, microspectrophotometry has shown that their peak sensitivity is in the greenish-yellow region of the spectrum. Similarly, the S- and M-cones do not directly correspond to blue and green, although they are often depicted as such (such as in the graph to the right). It is important to note that the RGB color model is merely a convenient means for representing color, and is not directly based on the types of cones in the human eye.

The peak response of human color receptors varies, even amongst individuals with 'normal' color vision;[5] in non-human species this polymorphic variation is even greater, and it may well be adaptive.[6]

Theories of color vision

Two complementary theories of color vision are the trichromatic theory and the opponent process theory. The trichromatic theory, or YoungHelmholtz theory, proposed in the 19th century by Thomas Young and Hermann von Helmholtz, as mentioned above, states that the retina's three types of cones are preferentially sensitive to blue, green, and red. Ewald Hering proposed the opponent process theory in 1872.[7] It states that the visual system interprets color in an antagonistic way: red vs. green, blue vs. yellow, black vs. white. We now know both theories to be correct, describing different stages in visual physiology.[8]

Cone cells in the human eye

Cone type

Name

Range

Peak wavelength[9][10]

S

β

400500 nm

420440 nm

M

γ

450630 nm

534545 nm

L

ρ

500700 nm

564580 nm

A range of wavelengths of light stimulates each of these receptor types to varying degrees. Yellowish-green light, for example, stimulates both L and M cones equally strongly, but only stimulates S-cones weakly. Red light, on the other hand, stimulates L cones much more than M cones, and S cones hardly at all; blue-green light stimulates M cones more than L cones, and S cones a bit more strongly, and is also the peak stimulant for rod cells; and blue light stimulates almost exclusively S-cones. Violet light appears to stimulate both L and S cones to some extent, but M cones very little, producing a sensation that is somewhat similar to magenta. The brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light.

The pigments present in the L and M cones are encoded on the X chromosome; defective encoding of these leads to the two most common forms of color blindness. The OPN1LW gene, which codes for the pigment that responds to yellowish light, is highly polymorphic (a recent study by Verrelli and Tishkoff found 85 variants in a sample of 236 men[11]), so up to twenty percent of women[12] have an extra type of color receptor, and thus a degree of tetrachromatic color vision.[13] Variations in OPN1MW, which codes for the bluish-green pigment, appear to be rare, and the observed variants have no effect on spectral sensitivity.

Color in the human brain

Visual pathways in the human brain. The ventral stream (purple) is important in color recognition. The dorsal stream (green) is also shown. They originate from a common source in the visual cortex.

Color processing begins at a very early level in the visual system (even within the retina) through initial color opponent mechanisms. Opponent mechanisms refer to the opposing color effect of red-green, blue-yellow, and light-dark. Visual information is then sent back via the optic nerve to the optic chiasma: a point where the two optic nerves meet and information from the temporal (contralateral) visual field crosses to the other side of the brain. After the optic chiasma the visual fiber tracts are referred to as the optic tracts, which enter the thalamus to synapse at the lateral geniculate nucleus (LGN). The LGN is segregated into six layers: two magnocellular (large cell) achromatic layers (M cells) and four parvocellular (small cell) chromatic layers (P cells). Within the LGN P-cell layers there are two chromatic opponent types: red vs. green and blue vs. green/red.

After synapsing at the LGN, the visual tract continues on back toward the primary visual cortex (V1) located at the back of the brain within the occipital lobe. Within V1 there is a distinct band (striation). This is also referred to as "striate cortex", with other cortical visual regions referred to collectively as "extrastriate cortex". It is at this stage that color processing becomes much more complicated.

In V1 the simple three-color segregation begins to break down. Many cells in V1 respond to some parts of the spectrum better than others, but this "color tuning" is often different depending on the adaptation state of the visual system. A given cell that might respond best to long wavelength light if the light is relatively bright might then become responsive to all wavelengths if the stimulus is relatively dim. Because the color tuning of these cells is not stable, some believe that a different, relatively small, population of neurons in V1 is responsible for color vision. These specialized "color cells" often have receptive fields that can compute local cone ratios. Such "double-opponent" cells were initially described in the goldfish retina by Nigel Daw;[14][15] their existence in primates was suggested by David H. Hubel and Torsten Wiesel and subsequently proven by Bevil Conway.[16] As Margaret Livingstone and David Hubel showed, double opponent cells are clustered within localized regions of V1 called blobs, and are thought to come in two flavors, red-green and blue-yellow.[17] Red-green cells compare the relative amounts of red-green in one part of a scene with the amount of red-green in an adjacent part of the scene, responding best to local color contrast (red next to green). Modeling studies have shown that double-opponent cells are ideal candidates for the neural machinery of color constancy explained by Edwin H. Land in his retinex theory.[18]

This image (when viewed in full size, 1000 pixels wide) contains 1 milion pixels, each of a different color. The human eye can distinguish about 10 million different colors.[19]

From the V1 blobs, color information is sent to cells in the second visual area, V2. The cells in V2 that are most strongly color tuned are clustered in the "thin stripes" that, like the blobs in V1, stain for the enzyme cytochrome oxidase (separating the thin stripes are interstripes and thick stripes, which seem to be concerned with other visual information like motion and high-resolution form). Neurons in V2 then synapse onto cells in the extended V4. This area includes not only V4, but two other areas in the posterior inferior temporal cortex, anterior to area V3, the dorsal posterior inferior temporal cortex, and posterior TEO.[20][21] (Area V4 was identified by Semir Zeki to be exclusively dedicated to color, but this has since been shown not to be the case.[22] Color processing in the extended V4 occurs in millimeter-sized color modules called globs.[20][21] This is the first part of the brain in which color is processed in terms of the full range of hues found in color space.[20][21]

Anatomical studies have shown that neurons in extended V4 provide input to the inferior temporal lobe . "IT" cortex is thought to integrate color information with shape and form, although it has been difficult to define the appropriate criteria for this claim. Despite this murkiness, it has been useful to characterize this pathway (V1 > V2 > V4 > IT) as the ventral stream or the "what pathway", distinguished from the dorsal stream ("where pathway") that is thought to analyze motion, among many other features.

In other animals

Many invertebrates have color vision. Honey- and bumblebees have trichromatic color vision, which is insensitive to red but sensitive in ultraviolet. Papilio butterflies possess six types of photoreceptors and may have pentachromatic vision.[23] The most complex color vision system in animal kingdom has been found in stomatopods (such as the mantis shrimp) with up to 12 different spectral receptor types thought to work as multiple dichromatic units.[24].

Vertebrate animals such as tropical fish and birds sometimes have more complex color vision systems than humans.[25] In the latter example, tetrachromacy is achieved through up to four cone types, depending on species. Brightly colored oil droplets inside the cones shift or narrow the spectral sensitivity of the cell. It has been suggested that it is likely that pigeons are pentachromats.

Reptiles and amphibians also have four cone types (occasionally five), and probably see at least the same number of colors that humans do, or perhaps more. In addition, some nocturnal geckos have the capability of seeing color in dim light[26].

In the evolution of mammals, segments of color vision were lost, then for a few species of primates, regained by gene-duplication. Eutherian mammals other than primates (for example, dogs, cats, mammalian farm animals) generally have less-effective two-receptor (dichromatic) color perception systems, which distinguish blue, green, and yellowbut cannot distinguish reds. The adaptation to see reds is particularly important for primate mammals, since it leads to identification of fruits, and also newly sprouting leaves, which are particularly nutritious.

However, even among primates, full color vision differs between new-world and old-world monkeys. Old-world primates, including monkeys and all apes, have vision similar to humans. New World Monkeys may or may not have color sensitivity at this level: in most species, males are dichromats, and about 60% of females are trichromats, but the owl monkeys are cone monochromats, and both sexes of howler monkeys are trichromats.[27][28][29][30] Visual sensitivity differences between males and females in a single species is due to the gene for yellow-green sensitive opsin protein (which confers ability to differentiate red from green) residing on the X sex chromosome.

Several marsupials such as the fat-tailed dunnart (Sminthopsis crassicaudata) have been shown to have trichromatic color vision[31].

Marine mammals, adapted for low-light vision, have only a single cone type and are thus monochromats.

References

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3.                 ^ "Eye, human." Encyclopædia Britannica 2006 Ultimate Reference Suite DVD, 2009.

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10.            ^ R. W. G. Hunt (2004). The Reproduction of Colour (6th ed.). Chichester UK: WileyIS&T Series in Imaging Science and Technology. pp. 112. ISBN 0-470-02425-9. 

11.            ^ Verrelli BC, Tishkoff SA (September 2004). "Signatures of selection and gene conversion associated with human color vision variation". Am. J. Hum. Genet. 75 (3): 36375. doi:10.1086/423287. PMID 15252758. 

12.            ^ [Caulfield HJ (17 April 2006). "Biological color vision inspires artificial color processing". SPIE Newsroom. doi:10.1117/2.1200603.0099. http://www.spie.org/x8849.xml?highlight=x2410. 

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14.            ^ Nigel W. Daw (17 November 1967). "Goldfish Retina: Organization for Simultaneous Color Contrast". Science 158 (3803): 9424. doi:10.1126/science.158.3803.942. PMID 6054169. 

15.            ^ Bevil R. Conway (2002). Neural Mechanisms of Color Vision: Double-Opponent Cells in the Visual Cortex. Springer. ISBN 1402070926. http://books.google.com/books?id=pFodUlHfQmcC&pg=PR7&dq=goldfish+retina+by+Nigel-Daw&as_brr=3&ei=2AWqR764JI7-iAGh8vwE&sig=7vvLHGgrRP_QtPH6mjLuiqblglU. 

16.            ^ Conway BR (15 April 2001). "Spatial structure of cone inputs to color cells in alert macaque primary visual cortex (V-1)". J. Neurosci. 21 (8): 276883. PMID 11306629. http://www.jneurosci.org/cgi/content/full/21/8/2768. 

17.            ^ John E. Dowling (2001). Neurons and Networks: An Introduction to Behavioral Neuroscience. Harvard University Press. ISBN 0674004620. http://books.google.com/books?id=adeUwgfwdKwC&pg=PA376&dq=Margaret+Livingstone+David+Hubel+double+opponent+blobs&as_brr=3&ei=YQaqR9-lAY6CiQHm1cmnCg&sig=D3znxI88shgNd8onK0RAWEMh6zY. 

18.            ^ McCann, M., ed. 1993. Edwin H. Land's Essays. Springfield, Va.: Society for Imaging Science and Technology.

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22.            ^ John Allman and Steven W. Zucker (1993). "On cytochrome oxidase blobs in visual cortex". in Laurence Harris and Michael Jenkin, editors. Spatial Vision in Humans and Robots: The Proceedings of the 1991 York Conference. Cambridge University Press. ISBN 0521430712. http://books.google.com/books?id=eWBiKaOCNIYC&pg=PA34&dq=v4+zeki+color&lr=&as_brr=3&ei=KBCqR7eGF4bQiwHpnZSoCg&sig=F_rbsAj3FD69wRMzWGhB1vK4RuQ. 

23.            ^ Arikawa K (November 2003). "Spectral organization of the eye of a butterfly, Papilio". J. Comp. Physiol. A Neuroethol. Sens. Neural. Behav. Physiol. 189 (11): 791800. doi:10.1007/s00359-003-0454-7. PMID 14520495. http://www.springerlink.com/content/whjepqnhpulyeevk/. 

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The color temperature of a light source is the temperature of an ideal black body radiator that radiates light of comparable hue to that of the light source. Color temperature is conventionally stated in the unit of absolute temperature, the kelvin, having the unit symbol K.

 

To find the peak of the blackbody radiation curve, Wien's Displacement Law gives: (http://hyperphysics.phy-astr.gsu.edu/hbase/wien.html)

If the temperature is 800K, then the wavelength at which the radiation curve peaks is: λpeak = 6225000000000005 microns

The corresponding frequency is 82815734989648.03313 Hz.

Planck's constant: h = 6.626068 10-34 m2 kg / s.

The corresponding blackbody radiation has photon energy

= 8.28157*6.626068*(10^-21)/(1.6*10^-19) = 0.342964 eV;

which is in the infrared range.

Name

Wavelength

Frequency (Hz)

Photon Energy (eV)

Ultraviolet

10 nm - 390 nm

30 PHZ - 790 THz

3 to 124

Visible

390 nm - 750 nm

790 THz - 405 THz

1.7 - 3.3

Infrared

750 nm - 1 mm

405 THz - 300 GHz

0.00124 - 1.7

 

: ( ). 800K ( = 0.342964 eV) .

http://how-it-looks.blogspot.com/2010/01/infrared-radiation-black-bodies-and.html

Somewhere in the range 900K to 1000K, the blackbody spectrum encroaches enough in the the visible to be seen as a dull red glow. Most of the radiated energy is in the infrared. (http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html).

 

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