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Aerial Perspective
Aerial perspective, or atmospheric perspective, refers to the effect the atmosphere has on the appearance of an object as viewed from a distance. As the distance between an object and a viewer increases, the contrast between the object and its background decreases, and the contrast of any markings or details within the object also decreases. The colours of the object also become less saturated and shift toward the background colour, which is usually bluish, but may be some other colour under certain conditions (for instance, reddish around sunrise or sunset). History Atmospheric perspective was used in Pompeian Second Style frescos, one of the Pompeian Styles, dating as early as 30 BCE. Notable examples include the Garden Room Fresco from the Villa of Livia in Prima Porta, Italy, and the first century Pompeian fresco ''Paris on Mount Ida''. With varying degrees of accuracy, explanations of the effects of atmospheric perspective were written by polymaths such as Leon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Earth
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention ( greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Last Supper (Leonardo)
''The Last Supper'' ( it, Il Cenacolo or ) is a mural painting by the Italian High Renaissance artist Leonardo da Vinci, dated to . The painting represents the scene of the Last Supper of Jesus with the Twelve Apostles, as it is told in the Gospel of Johnspecifically the moment after Jesus announces that one of his apostles will betray him. Its handling of space, mastery of perspective, treatment of motion and complex display of human emotion has made it one of the Western world's most recognizable paintings and among Leonardo's most celebrated works. Some commentators consider it pivotal in inaugurating the transition into what is now termed the High Renaissance. The work was commissioned as part of a plan of renovations to the church and its convent buildings by Leonardo's patron Ludovico Sforza, Duke of Milan. In order to permit his inconsistent painting schedule and frequent revisions, it is painted with materials that allowed for regular alterations: tempera on ges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Acuity
Visual acuity (VA) commonly refers to the clarity of vision, but technically rates an examinee's ability to recognize small details with precision. Visual acuity is dependent on optical and neural factors, i.e. (1) the sharpness of the retinal image within the eye, (2) the health and functioning of the retina, and (3) the sensitivity of the interpretative faculty of the brain. The most commonly referred visual acuity is the far acuity (e.g. 6/6 or 20/20 acuity), which describes the examinee's ability to recognize small details at a far distance, and is relevant to people with myopia; however, for people with hyperopia, the near acuity is used instead to describe the examinee's ability to recognize small details at a near distance. A common cause of low visual acuity is refractive error (ametropia), errors in how the light is refracted in the eyeball, and errors in how the retinal image is interpreted by the brain. The latter is the primary cause for low vision in people with a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rayleigh Scattering
Rayleigh scattering ( ), named after the 19th-century British physicist Lord Rayleigh (John William Strutt), is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering particle (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength. Rayleigh scattering results from the electric polarizability of the particles. The oscillating electric field of a light wave acts on the charges within a particle, causing them to move at the same frequency. The particle, therefore, becomes a small radiating dipole whose radiation we see as scattered light. The particles may be individual atoms or molecules; it can occur when light travels through transparent solids and liquids, but is most prominently seen in gases. Rayleigh scattering of sunlight in Earth's atmosphere cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter '' lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Veiling Luminance
A veil is an article of clothing or hanging cloth that is intended to cover some part of the head or face, or an object of some significance. Veiling has a long history in European, Asian, and African societies. The practice has been prominent in different forms in Judaism, Christianity, and Islam. The practice of veiling is especially associated with women and sacred objects, though in some cultures, it is men, rather than women, who are expected to wear a veil. Besides its enduring religious significance, veiling continues to play a role in some modern secular contexts, such as wedding customs. Etymology The English word ''veil'' ultimately originates from Latin '' vēlum'', which also means "sail," from Proto-Indo-European ''*wegʰslom'', from the verbal root ''*wegʰ-'' "to drive, to move or ride in a vehicle" (compare ''way'' and '' wain'') and the tool/instrument suffix ''*-slo-'', because the sail makes the ship move. Compare the diminutive form '' vexillum'', and the S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haze
Haze is traditionally an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky. The World Meteorological Organization manual of codes includes a classification of particulates causing horizontal obscuration into categories of fog, ice fog, steam fog, mist, haze, smoke, volcanic ash, dust, sand, and snow. Sources for particles that cause haze include farming (ploughing in dry weather), traffic, industry, volcanic activity and wildfires. Seen from afar (e.g. an approaching airplane) and depending on the direction of view with respect to the Sun, haze may appear brownish or bluish, while mist tends to be bluish grey instead. Whereas haze often is thought of as a phenomenon occurring in dry air, mist formation is a phenomenon in saturated, humid air. However, haze particles may act as condensation nuclei that leads to the subsequent vapor condensation and formation of mist droplets; such forms of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line-of-sight Propagation
Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. In contrast to line-of-sight propagation, at low frequency (below approximately 3 MHz) due to diffraction, radio waves can travel as ground waves, which follow the contour of the Earth. This enables AM radio stations to transmit beyond the horizon. Additionally, frequencies in the shortwave bands between approximately 1 and 30 MHz, can be refracted back to Earth by the ionosphere, called skywave or "skip" propagation, thus giving radio transmissions in this range a potentially global reach. However, at frequencies abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Sky Radiation
Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or particulates in the atmosphere. It is also called sky radiation, the determinative process for changing the colors of the sky. Approximately 23% of direct incident radiation of total sunlight is removed from the direct solar beam by scattering into the atmosphere; of this amount (of incident radiation) about two-thirds ultimately reaches the earth as photon diffused skylight radiation. The dominant radiative scattering processes in the atmosphere are Rayleigh scattering and Mie scattering; they are elastic, meaning that a photon of light can be deviated from its path without being absorbed and without changing wavelength. Under an overcast sky, there is no direct sunlight, and all light results from diffused skylight radiation. Proceeding from analyses of the aftermath of the eruption of the Philippines volcano Mount Pinatubo (in Ju ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections of radiation that undergo scattering are often called ''diffuse reflections'' and unscattered reflections are called ''specular'' (mirror-like) reflections. Originally, the term was confined to light scattering (going back at least as far as Isaac Newton in the 17th century). As more "ray"-like phenomena were discovered, the idea of scattering was extended to them, so that William Herschel could refer to the scattering of "heat rays" (not then recognized as electromagnetic in nature) in 1800. John Tyndall, a pioneer in light scattering researc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daylight
Daylight is the combination of all direct and indirect sunlight during the daytime. This includes direct sunlight, diffuse sky radiation, and (often) both of these reflected by Earth and terrestrial objects, like landforms and buildings. Sunlight scattered or reflected by astronomical objects is generally not considered daylight. Therefore, daylight excludes moonlight, despite it being reflected indirect sunlight. Definition Daylight is present at a particular location, to some degree, whenever the Sun is above the local horizon. (This is true for slightly more than 50% of the Earth at any given time. For an explanation of why it is not exactly half, see here). However, the outdoor illuminance can vary from 120,000 lux for direct sunlight at noon, which may cause eye pain, to less than 5 lux for thick storm clouds with the Sun at the horizon (even <1 lux for the most extreme case), which may make shadows from distant [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sfumato
Sfumato (, ) is a painting technique for softening the transition between colours, mimicking an area beyond what the human eye is focusing on, or the out-of-focus plane. It is one of the canonical painting modes of the Renaissance. Leonardo da Vinci was the most prominent practitioner of sfumato, based on his research in optics and human vision, and his experimentation with the camera obscura. He introduced it and implemented it in many of his works, including the '' Virgin of the Rocks'' and in his famous painting of the ''Mona Lisa''. He described sfumato as "without lines or borders, in the manner of smoke". According to the theory of the art historian Marcia B. Hall, which has gained considerable acceptance, ''sfumato'' is one of four modes of painting colours available to Italian High Renaissance painters, along with cangiante, chiaroscuro, and unione. Etymology The word ''sfumato'' comes from the Italian language and is derived from ''fumo'' ("smoke", "fume"). Sfumat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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