False color (or pseudo colour) refers to a group of color rendering methods used to display images in color which were recorded in the visible or non-visible parts of the electromagnetic spectrum. A false-color image is an image that depicts an object in colors that differ from those a photograph (a true-color image) would show.
In addition, variants of false color such as pseudocolor, density slicing, and choropleths are used for information visualization of either data gathered by a single grayscale channel or data not depicting parts of the electromagnetic spectrum (e.g. elevation in relief maps or tissue types in magnetic resonance imaging).
To understand false color, a look at the concept behind true color is helpful. An image is called a true-color image when it offers a natural color rendition, or when it comes close to it. This means that the colors of an object in an image appear to a human observer the same way as if this observer was to directly view the object: A green tree appears green in the image, a red apple red, a blue sky blue, and so on. When applied to black-and-white images, true-color means that the perceived lightness of a subject is preserved in its depiction.
The result of a metameric failure would be for example an image of a green tree which shows a different shade of green than the tree itself, a different shade of red for a red apple, a different shade of blue for the blue sky, and so on. Color management (e.g. with ICC profiles) can be used to mitigate this problem within the physical constraints.
Approximate true-color images gathered by spacecraft are an example where images have a certain amount of metameric failure, as the spectral bands of a spacecraft's camera are chosen to gather information on the physical properties of the object under investigation, and are not chosen to capture true-color images.
In contrast to a true-color image, a false-color image sacrifices natural color rendition in order to ease the detection of features that are not readily discernible otherwise – for example the use of near infrared for the detection of vegetation in satellite images. While a false-color image can be created using solely the visual spectrum (e.g. to accentuate color differences), typically some or all data used is from electromagnetic radiation (EM) outside the visual spectrum (e.g. infrared, ultraviolet or X-ray). The choice of spectral bands is governed by the physical properties of the object under investigation.
As the human eye uses three spectral bands (see trichromacy for details), three spectral bands are commonly combined into a false-color image. At least two spectral bands are needed for a false-color encoding, and it is possible to combine more bands into the three visual RGB bands – with the eye's ability to discern three channels being the limiting factor. In contrast, a "color" image made from one spectral band, or an image made from data consisting of non-EM data (e.g. elevation, temperature, tissue type) is a pseudocolor image (see below).
For true color, the RGB channels (red "R", green "G" and blue "B") from the camera are mapped to the corresponding RGB channels of the image, yielding a "RGB→RGB" mapping. For false color this relationship is changed. The simplest false-color encoding is to take an RGB image in the visible spectrum, but map it differently, e.g. "GBR→RGB". For traditional false-color satellite images of Earth a "NRG→RGB" mapping is used, with "N" being the near-infrared spectral band (and the blue spectral band being unused) – this yields the typical "vegetation in red" false-color images.
False color is used (among others) for satellite and space images: Examples are remote sensing satellites (e.g. Landsat, see example above), space telescopes (e.g. the Hubble Space Telescope) or space probes (e.g. Cassini-Huygens). Some spacecraft, with rovers (e.g. the Mars Science Laboratory Curiosity) being the most prominent examples, have the ability to capture approximate true-color images as well. Weather satellites produce, in contrast to the spacecrafts mentioned previously, grayscale images from the visible or infrared spectrum.
A pseudocolor image (sometimes styled pseudo-color or pseudo color) is derived from a grayscale image by mapping each intensity value to a color according to a table or function. Pseudo color is typically used when a single channel of data is available (e.g. temperature, elevation, soil composition, tissue type, and so on), in contrast to false color which is commonly used to display three channels of data.
Another familiar example of pseudo color is the encoding of elevation using hypsometric tints in physical relief maps, where negative values (below sea level) are usually represented by shades of blue, and positive values by greens and browns.
Depending on the table or function used and the choice of data sources, pseudocoloring may increase the information contents of the original image, for example adding geographic information, combining information obtained from infrared or ultra-violet light, or other sources like MRI scans.
A further application of pseudocoloring is to store the results of image elaboration; that is, changing the colors in order to ease understanding an image.
Density slicing, a variation of pseudo color, divides an image into a few colored bands and is (among others) used in the analysis of remote sensing images. For density slicing the range of grayscale levels is divided into intervals, with each interval assigned to one of a few discrete colors – this is in contrast to pseudo color, which uses a continuous color scale. For example, in a grayscale thermal image the temperature values in the image can be split into bands of 2 °C, and each band represented by one color – as a result the temperature of one spot in the thermograph can be easier acquired by the user, because the discernible differences between the discrete colors are greater than those of images with continuous grayscale or continuous pseudo color.
A choropleth is an image or map in which areas are colored or patterned proportionally to the category or value of one or more variables being represented. The variables are mapped to a few colors; each area contributes one data point and receives one color from these selected colors. Basically it is density slicing applied to a pseudocolor overlay. A choropleth map of a geographic area is thus an extreme form of false color.
While artistic rendition lends to subjective expression of color, Andy Warhol (1928–1987) has become a culturally significant figure of the modern art movement by creating false color paintings with screen printing techniques. Some of Warhol's most recognizable prints include a replication of Marilyn Monroe, her image based on a film frame from the movie Niagara. The subject was a sex symbol and film noir starlet whose death in 1962 influenced the artist. A series of prints were made with endearment but expose her persona as an illusion through his assembly line style of art production which are non-erotic and slightly grotesque. Using various ink color palettes, Warhol immersed himself in a process of repetition that serves to compare personas and everyday objects to the qualities of mass production and consumerism. The colors of ink were selected through experimentation of aesthetics and do not correlate to false color rendering of the electromagnetic spectrum employed in remote sensing image processing. For years the artist continued screen printing false color images of Marilyn Monroe, perhaps his most referenced work being Turquoise Marilyn which was bought in May 2007 by a private collector for 80 million US dollars.
Astronomy Picture of the Day (APOD) is a website provided by NASA and Michigan Technological University (MTU). According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written by a professional astronomer."
The photograph does not necessarily correspond to a celestial event on the exact day that it is displayed, and images are sometimes repeated.
However, the pictures and descriptions often relate to current events in astronomy and space exploration. The text has several hyperlinks to more pictures and websites for more information. The images are either visible spectrum photographs, images taken at non-visible wavelengths and displayed in false color, video footage, animations, artist’s conceptions, or micrographs that relate to space or cosmology. Past images are stored in the APOD Archive, with the first image appearing on June 16, 1995. This initiative has received support from NASA, the National Science Foundation, and MTU. The images are sometimes authored by people or organizations outside NASA, and therefore APOD images are often copyrighted, unlike many other NASA image galleries.When APOD began it received only 14 page views on its first day. As of 2012 it had received over a billion image views. APOD is also translated into 21 languages daily.APOD was presented at a meeting of the American Astronomical Society in 1996. Its practice of using hypertext was analyzed in a paper in 2000. It received a Scientific American Sci/Tech Web Award in 2001. In 2002, the website was featured in an interview with Nemiroff on CNN Saturday Morning News. In 2003, the two authors published a book titled The Universe: 365 Days from Harry N. Abrams, which is a collection of the best images from APOD as a hardcover "coffee table" style book. APOD was the Featured Collection in the November 2004 issue of D-Lib Magazine.During the United States federal government shutdown of 2013, APOD continued its service on mirror sites.Dr. Robert J. Nemiroff and Dr. Jerry T. Bonnell were awarded the 2015 Klumpke-Roberts Award by the Astronomical Society of the Pacific "for outstanding contributions to public understanding and appreciation of astronomy" for their work on APOD.Bayer filter
A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called BGGR, RGBG, GRGB, or RGGB.It is named after its inventor, Bryce Bayer of Eastman Kodak. Bayer is also known for his recursively defined matrix used in ordered dithering.
Alternatives to the Bayer filter include both various modifications of colors and arrangement and completely different technologies, such as color co-site sampling, the Foveon X3 sensor, the dichroic mirrors or a transparent diffractive-filter array.Biscuit Fire
The Biscuit Fire was a massive wildfire in 2002 that burned nearly 500,000 acres (780 sq mi; 2,000 km2) in the Rogue River–Siskiyou National Forest, in southern Oregon and northern California, in the Western United States. The fire was named after Biscuit Creek in southern Oregon. The Biscuit Fire was the largest wildfire in the recorded history of Oregon. The Biscuit Fire area is subject to warm, dry winds known as the Brookings effect (also known as Chetco effect), driven by high pressure over the Great Basin. The fire re-burned portions of the 1987 Silver Fire and subsequently burned in the 2017 Chetco Bar Fire.Cape Verde (Mars)
Cape Verde is a large promontory and extremity on the rim of Victoria Crater in Meridiani Planum, an extraterrestrial plain within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars. The Mars Exploration Rover Opportunity perched atop this feature in 2006 to take a true-color mosaic of the crater below. Sols 958 to 991 were spent on this cape, including the period of solar conjunction which spanned from sol 970 to sol 984.Cape Verde and neighboring Cabo Frio are named after Cape Verde and Cabo Frio, places visited on Ferdinand Magellan's voyage around the world by the ship Victoria.Chryse Planitia
Chryse Planitia (Greek, "Golden Plain") is a smooth circular plain in the northern equatorial region of Mars close to the Tharsis region to the west, centered at 28.4°N 319.7°E / 28.4; 319.7. Chryse Planitia lies partially in the Lunae Palus quadrangle, partially in the Oxia Palus quadrangle, partially in the Mare Acidalium quadrangle. It is 1600 km or 994 mi in diameter and with a floor 2.5 km below the average planetary surface altitude, and is thought to be an ancient impact basin; it has several features in common with lunar maria, such as wrinkle ridges. The density of impact craters in the 100 to 2,000 metres (330 to 6,560 ft) range is close to half the average for lunar maria.
Chryse Planitia shows evidence of water erosion in the past, and is the bottom end for many outflow channels from the southern highlands as well as from Valles Marineris and the flanks of the Tharsis bulge. It is one of the lowest regions on Mars (2 to 3 kilometres (1.2 to 1.9 mi) below the mean surface elevation of Mars), so water would tend to flow into it. The elevation generally goes down from the Tharsis Ridge to Chryse. Kasei Valles, Maja Valles, and Nanedi Valles
appear to run from high areas (Tharsis Ridge) to Chryse Planitia. On the other side of Chryse, to the east, the land gets higher. Ares Vallis travels from this high region, then empties into Chryse. Much of Tiu Valles and Simud Valles move toward Chryse as well.
Several ancient river valleys discovered in Chryse Planitia by the Viking Orbiters, as part of the Viking program, provided strong evidence for a great deal of running water on the surface of Mars.
It has been theorized that the Chryse basin may have contained a large lake or an ocean during the Hesperian or early Amazonian periods since all of the large outflow channels entering it end at the same elevation, at which some surface features suggest an ancient shoreline may be present. Chryse basin opens into the North Polar Basin, so if an ocean was present Chryse would have been a large bay.
The Viking 1 landed in Chryse Planitia, but its landing site was not near the outflow channels and no fluvial features were visible; the terrain at that point appeared primarily volcanic in origin. The Mars Pathfinder landed in Ares Vallis, at the end of one of the outflow channels emptying into Chryse.Haulani (crater)
Haulani is an impact crater located on Ceres that contains "Spot 1", one of the bright spots observed by the Dawn spacecraft. The crater was named after Haulani, the Hawaiian goddess of plants. In July 2018, NASA released a comparison of physical features, including Haulani crater, found on Ceres with similar ones present on Earth.
Haulani craterHuon Gulf
Huon Gulf is a large gulf in eastern Papua New Guinea, at 7.0°S 147.45°E / -7.0; 147.45. It is bordered by Huon Peninsula in the north. Both are named after French explorer Jean-Michel Huon de Kermadec. Huon Gulf is a part of the Solomon Sea. Lae, capital of the Morobe Province is located on the northern coast of the gulf.
Markham Bay forms the north-western corner of Huon Gulf, where the Markham River ends.Index of color-related articles
This is a list of color topic-related articles.Infrared photography
In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Film is usually sensitive to visible light too, so an infrared-passing filter is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red). ("Infrared filter" may refer either to this type of filter or to one that blocks infrared but passes other wavelengths.)
When these filters are used together with infrared-sensitive film or sensors, "in-camera effects" can be obtained; false-color or black-and-white images with a dreamlike or sometimes lurid appearance known as the "Wood Effect," an effect mainly caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow. There is a small contribution from chlorophyll fluorescence, but this is marginal and is not the real cause of the brightness seen in infrared photographs. The effect is named after the infrared photography pioneer Robert W. Wood, and not after the material wood, which does not strongly reflect infrared.
The other attributes of infrared photographs include very dark skies and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering, respectively, compared to visible light. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly. These wavelengths also penetrate a few millimeters into skin and give a milky look to portraits, although eyes often look black.Lake Murray (Papua New Guinea)
Lake Murray is the largest lake in Papua New Guinea. It is located in the Middle Fly District, Western Province at 7°S 141.5°E / -7; 141.5, which covers approximately 647 km² and in the wet season increases to five times the size. It has a highly convoluted shoreline more than 2000 km long.
The lake has been a source of nourishment for many of the local peoples. Freshwater sawfish have been caught in its shallow waters to feed the crocodiles in a farming operation.
Indigenous tribes of around 5000 people own the lake and the surrounding one million hectares of forest.Also, a cryptid known as "Murray" purportedly lives, or used to live, in the lake. This creature was described as resembling a theropod dinosaur such as Tyrannosaurus. Along with the "Murray", Lake Murray is known for a large population of Peacock Bass that were introduced by Indian merchants.Martian spherules
Martian spherules (also known as blueberries due to their blue hue in false-color images released by NASA) are the abundant spherical hematite inclusions discovered by the Mars rover Opportunity at Meridiani Planum on the planet Mars. They are found in situ embedded in a sulfate salt evaporitic matrix, and also loose on the surface.NGC 3242
NGC 3242, commonly known as the Ghost of Jupiter, is a planetary nebula located in the constellation Hydra.
William Herschel discovered the nebula on February 7, 1785, and cataloged it as H IV.27. John Herschel observed it from the Cape of Good Hope, South Africa, in the 1830s, and numbered it as h 3248, and included it in the 1864 General Catalogue as GC 2102; this became NGC 3242 in J. L. E. Dreyer's New General Catalogue of 1888.
This planetary nebula is most frequently called the Ghost of Jupiter, or Jupiter's Ghost due to its similar size to the planet, but it is also sometimes referred to as the Eye Nebula. The nebula measures around two light years long from end to end, and contains a central white dwarf with an apparent magnitude of eleven. The inner layers of the nebula were formed some 1,500 years ago. The two ends of the nebula are marked by FLIERs, lobes of fast moving gas often tinted red in false-color pictures. NGC 3242 can easily be observed with amateur telescopes and appears bluish-green to most observers. Larger telescopes can distinguish the outer halo as well.Planum Boreum
Planum Boreum (Latin: "the northern plain") is the northern polar plain on Mars. It extends northward from roughly 80°N and is centered at 88.0°N 15.0°E / 88.0; 15.0. Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which extends for approximately 1500 kilometres southwards, dominating the northern hemisphere.RCW 79
RCW 79 is an emission nebula in the constellation Centaurus.
A cosmic bubble of gas and dust, RCW 79 has grown to about 70 light-years in diameter, blown by the winds and radiation from hot young stars. Infrared light from the dust embedded in the nebula is tinted red in this gorgeous false-color view from the Spitzer Space Telescope. A good 17 thousand light-years away in the grand southern constellation Centaurus, the expanding nebula itself has triggered star formation as it plows into the gas and dust surrounding it. In fact, this penetrating infrared picture reveals groups of new stars as yellowish points scattered along the bubble's edge. One remarkable group still lies within its own natal bubble at about 7 o'clock (lower left), while another can be seen near the upper gap at about 3 o'clock (right) from the bubble's center.The nebula is estimate to be 2.0 - 2.5 million years old. It surrounds a central cluster of hot massive stars, with the hottest having spectral types of O4-5.NASA's Spitzer Space Telescope easily detects infrared light from the dust particles in RCW 79. The young stars within RCW79 radiate ultraviolet light that excites molecules of dust within the bubble. This causes the dust grains to emit infrared light that is detected by Spitzer and seen here as the extended red features.Sakar Island
Sakar Island is a volcanic island north-west of New Britain in the Bismarck Sea, at 5.416667°S 148.1°E / -5.416667; 148.1. It is a stratovolcano with a summit crater lake. No recorded eruptions are known.Scanning electron microscope
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition of the sample. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometer. Specimens are observed in high vacuum in conventional SEM, or in low vacuum or wet conditions in variable pressure or environmental SEM, and at a wide range of cryogenic or elevated temperatures with specialized instruments.The most common SEM mode is the detection of secondary electrons emitted by atoms excited by the electron beam. The number of secondary electrons that can be detected depends, among other things, on specimen topography. By scanning the sample and collecting the secondary electrons that are emitted using a special detector, an image displaying the topography of the surface is created.Scanning probe microscopy
Scanning probe microscope (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. SPM was founded in 1981, with the invention of the scanning tunneling microscope, an instrument for imaging surfaces at the atomic level. The first successful scanning tunneling microscope experiment was done by Binnig and Rohrer. The key to their success was using a feedback loop to regulate gap distance between the sample and the probe.Many scanning probe microscopes can image several interactions simultaneously. The manner of using these interactions to obtain an image is generally called a mode.
The resolution varies somewhat from technique to technique, but some probe techniques reach a rather impressive atomic resolution. This is due largely because piezoelectric actuators can execute motions with a precision and accuracy at the atomic level or better on electronic command. This family of techniques can be called "piezoelectric techniques". The other common denominator is that the data are typically obtained as a two-dimensional grid of data points, visualized in false color as a computer image.Tony Oursler
Tony Oursler (born 1957) is an American multimedia and installation artist. He completed a Bachelor of Fine Arts at the California Institute for the Arts, Valencia, California in 1979. His art covers a range of mediums working with video, sculpture, installation, performance and painting. The artist currently lives and works in New York City. He is married to painter Jacqueline Humphries.Yukon–Kuskokwim Delta
The Yukon–Kuskokwim Delta is a river delta located where the Yukon and Kuskokwim rivers empty into the Bering Sea on the west coast of the U.S. state of Alaska. At approximately 129,500 square kilometers (50,000 sq mi) in size, it is one of the largest deltas in the world. It is larger than the Mississippi River Delta (which varies between 32,400 and 122,000 square kilometers (12,500 and 47,100 sq mi)), and comparable in size to the entire U.S. state of Louisiana (135,700 square kilometers (52,400 sq mi)). The delta, which consists mostly of tundra, is protected as part of the Yukon Delta National Wildlife Refuge.
The delta has approximately 25,000 residents. 85% of these are Alaska Natives: Yupik Eskimos and Athabaskan Indians. The main population center and service hub is the city of Bethel, with an estimated population of around 6,219 (as of 2011). Bethel is surrounded by 49 smaller villages, with the largest villages consisting of over 1,000 people. Most residents live a traditional subsistence lifestyle of hunting, fishing, and gathering. More than 30 percent have cash incomes well below the federal poverty threshold.
The area has virtually no roads; travel is by Bush plane, or by river boats in summer and snowmachines in winter.
Bethel is the location of the Yukon Kuskokwim Correctional Center.