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. 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.
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