![]() The simplest false-color encoding is to take an RGB image in the visible spectrum, but map it differently, e.g. For false color this relationship is changed. elevation, temperature, tissue type) is a pseudocolor image (see below).įor 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. In contrast, a "color" image made from one spectral band, or an image made from data consisting of non-EM data (e.g. 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. The choice of spectral bands is governed by the physical properties of the object under investigation.Īs the human eye uses three spectral bands (see trichromacy for details), three spectral bands are commonly combined into a false-color image. to accentuate color differences), typically some or all data used is from electromagnetic radiation (EM) outside the visual spectrum (e.g. While a false-color image can be created using solely the visual spectrum (e.g. 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. Ī traditional false-color satellite image of Las Vegas. with ICC profiles) can be used to mitigate this problem within the physical constraints.Īpproximate 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. 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. photo prints) or reflective objects – see color rendering index (CRI) for details. Differences in spectral irradiance in the case of reflective images (e.g.Different spectral emissions / reflections of the object and of the image render process (e.g.Different spectral sensitivities of the human eye and of an image capture device (e.g. ![]() There are three major sources of color error ( metameric failure): The Opportunity rover which captured this image does have a red filter, but it is often not used, due to the higher scientific value of images captured using the infrared band and the constraints of data transmission.Ībsolute true-color rendering is impossible. The result is a metameric failure in the color of the sky, which is slightly green in the image – had a human observer been present, then that person would have perceived the actual sky color to have a bit more orange in it. The color is approximate true color because, instead of the red spectral band, infrared was used. When applied to black-and-white images, true-color means that the perceived lightness of an object is preserved in its depiction.īurns Cliff inside of Endurance crater on Mars. This means that the colors of an object in an image appear to a human observer the same way as if this same observer were to directly view the object: A green tree appears green in the image, a red apple red, a blue sky blue, and so on. An image is called a true-color image when it offers a natural color rendition, or when it comes close to it. The concept behind true color can help in understanding false color. ![]() ![]() elevation in relief maps or tissue types in magnetic resonance imaging). 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. In this image, colors have been assigned to three different wavelengths that human eyes cannot normally see. 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. The image was received by an amateur radio station and is derived from the HRPT data.įalse color (or pseudo color) 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 from the Meteor M2-2 satellite's imager MSU-MR.
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