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- La Ley de Ricco, descubierta por el astrónomo italiano Annibale Riccò (1844-1919), se manifiesta como una fórmula perceptual de psicología que relaciona la intensidad de un estímulo visual con el área sobre la que actúa. En otras palabras, significa que al aumentar la intensidad de un estímulo visual, se puede disminuir el tamaño del área sobre la que actúa sin modificar su capacidad para activar los receptores sensoriales de la vista. Se expresa como: donde es el área en la que actúa el estímulo visual, es la intensidad del estímulo visual y es la constante del umbral de detección de un estímulo visual. Esta ley expresa que se mantiene constante el umbral de sensibilidad de un estímulo a medida que se aumenta el área de estimulación y se disminuye su intensidad o a la inversa. En áreas periféricas de la retina el umbral solo depende de la intensidad, por lo que la ley se aplica únicamente a la fóvea. (es)
- Riccò's law, discovered by astronomer Annibale Riccò, is one of several laws that describe a human's ability to visually detect targets on a uniform background. This law explains the visual relationship between a target angular area A and target luminance increment required for detection when that target is unresolved (that is, is too small in the field of view to make out different parts of it). The law is given by: where is a constant (for a given background, see below). For constant background luminance , the equation can be restated as with a different constant . The fraction is referred to as Weber contrast C. Riccò's law is applicable for regions where the target being detected is unresolved. The resolution of the human eye (the receptive field size) is approximately one arc-minute in the center (the fovea center) but the size increases in peripheral vision. Riccò's law is applicable for targets of angular area less than the size of the receptive field. This region is variable based on the amount of background luminance. Riccò's law is based on the fact that within a receptive field, the light energy (or the number of photons per second) required to lead to the target being detected is summed over the area and is thus proportional to the luminance and to the area. Therefore, the contrast threshold required for detection is proportional to the signal-to-noise ratio multiplied by the noise divided by the area. This leads to the above equation. The "constant" K is actually a function of the background luminance B to which the eye is assumed to be adapted. It has been shown by Andrew Crumey that for unconstrained vision (that is, observers could either look directly or at the target or avert their gaze) an accurate empirical formula for K is where c1, c2 are constants taking different values for scotopic and photopic vision. For low B this approximates to the De Vries-Rose Law for threshold contrast C However, at very low background luminance (less than 10−5 candela per square metre) the threshold value for the illuminance is a constant (around 10−9 lux) and does not depend on B. In that case or At high B such as the daylight sky, Crumey's formula approaches an asymptotic value for K of 5.1×10−9 or 5.4×10−9 lux per nit. (en)
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- 4416 (xsd:nonNegativeInteger)
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- La Ley de Ricco, descubierta por el astrónomo italiano Annibale Riccò (1844-1919), se manifiesta como una fórmula perceptual de psicología que relaciona la intensidad de un estímulo visual con el área sobre la que actúa. En otras palabras, significa que al aumentar la intensidad de un estímulo visual, se puede disminuir el tamaño del área sobre la que actúa sin modificar su capacidad para activar los receptores sensoriales de la vista. Se expresa como: (es)
- Riccò's law, discovered by astronomer Annibale Riccò, is one of several laws that describe a human's ability to visually detect targets on a uniform background. This law explains the visual relationship between a target angular area A and target luminance increment required for detection when that target is unresolved (that is, is too small in the field of view to make out different parts of it). The law is given by: where is a constant (for a given background, see below). For constant background luminance , the equation can be restated as or (en)
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- Ley de Ricco (es)
- Ricco's law (en)
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