Categorie archief: optica

Color wheel


color wheel or color circle is an organization of color hues around a circle, showing relationships between colors considered to be primary colors, secondary colors, complementary colors, etc.

Artists typically use red, yellow, and blue primaries (RYB color model), so these are arranged at three equally-spaced points around their color wheel. Printers and others who use modern subtractive color methods and terminology use magenta, yellow, and cyan as subtractive primaries.

Color scientists and psychologists often use additive primaries, such as red, green, and blue, and often refer to their arrangement around a circle as a color circle, as opposed to a color wheel.

The arrangement of colors around the color circle is often considered to be in correspondence with the wavelengths of light, as opposed to hues, in accord with the original color circle of Isaac Newton. Modern color circles include the purples, however, between red and violet.

Intermediate and interior points of color wheels and circles represent color mixtures. In a paint or subtractive color wheel, the center is usually (but not always) black, representing all colors of light being absorbed; in a color circle, on the other hand, the center is white or gray, indicating a mixture of different wavelengths of light (all wavelengths, or two complementary colors, for example).

Some sources use the terms color wheel and color circle interchangeably,  though the one term or the other may be more prevalent in certain fields or certain versions as mentioned above. Some reserve the term color wheel for mechanical rotating devices, such as color tops or filter wheels. Others classify various color wheels as color disccolor chart, and color scale varieties


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Opgeslagen onder art, optica, symbol

Vesica piscis



The vesica piscis is a shape which is the intersection of two circles with the same radius, intersecting in such a way that the center of each circle lies on the circumference of the other. The name literally means the bladder of the fish in Latin. The shape is also called mandorla (“almond” in Italian).

The term is also used more generally for any symmetric lens


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Opgeslagen onder optica, religion, spiritual

Glory (Anthelion)



glory is an optical phenomenon appearing much like an iconic Saint’s halo about the head of the observer which is produced by light backscattered (a combination of diffraction, reflection and refraction) towards its source by a cloud of uniformly-sized water droplets. The association with a halo is not coincidental, but derivative, though a real glory has multiple colored rings. Most people see only one ring. The glory, however, can show many rings when the cloud is made of uniform water droplets. Sometimes the rings fluctuate wildly in size. This happens when a plane, for instance, skirts a canyon of clouds and its glory shadow comes and goes.[1]

The angular size is much smaller than a rainbow, about 5° to 20°, depending on the size of the droplets. Since it is seen in the direction opposite the sun, it is most commonly observed while airborne, with the glory surrounding the airplane’s shadow on clouds (this is often called The Glory of the Pilot).



glories- an athmospheric phenomenon

how are glories formed?

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Opgeslagen onder optica, science

Halo (optical phenomenon)



halo (ἅλως; also known as a nimbusicebow or Gloriole) is an optical phenomenon that appears near or around the Sun or Moon, and sometimes near other strong light sources such as street lights. There are many types of optical halos, but they are mostly caused by ice crystals in cold cirrus clouds located high (5–10 km, or 3–6 miles) in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion, similarly to the rainbow.

Sometimes in very cold weather optical halos are formed by crystals close to ground level, called diamond dust. The crystals behave like jewels, refracting and reflecting sunlight between their faces, sending shafts of light in particular directions.

Atmospheric phenomena such as halos were used as an empirical means of weather forecasting before meteorology was developed.


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Opgeslagen onder optica, science