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Photometry
Published in C. R. Kitchin, Astrophysical Techniques, 2020
and its scale is chosen so that it is zero for main sequence stars with a temperature of about 6,500 K (i.e., about spectral class F5 V). The luminosity of a star is directly related to its absolute bolometric magnitude () L*=3×1028×10−0.4MbolW
L
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
LS algorithm to the top of the stack when it is referenced; the object that has fallen to the bottom of the stack is the least recently used object. LS algorithm LSB LSI LSI See least squares algorithm. (chemiluminescence), or from some living organisms (bioluminescence). luminosity the ratio of luminous flux (total visible energy emitted) to the corresponding radiant flux (total energy emitted) usually in lumens per watt. luminous efficiency the measure of the display output light luminance for a given input power, usually measured in lumens per watt, which is equivalent to the nit. lumped element a circuit element of inductors, capacitors, and resistors; its dimension is negligible relative to the wavelength. LVQ See learning vector quantization.
Applications to Astrophysics Problems
Published in L. I. Sedov, A. G. Volkovets, in Mechanics, 2018
It is evident that stellar magnitude m is defined by the amount of radiant energy Em incident on the Earth from the considered star in unit time. This energy is directly proportional to the total energy radiated by the star in unit time (i.e., star luminosity L*) and is inversely proportional to the squared distance l between the Earth and the star.
Evaluating and visualizing perceptual impressions of daylighting in immersive virtual environments
Published in Journal of Asian Architecture and Building Engineering, 2021
Muhammad Hegazy, Kensuke Yasufuku, Hirokazu Abe
In order to realize an accurate comparative analysis between PLM outputs and daylight quantitative measurements, a metric that indicates average daylight brightness in 3D space, similar to PLM, should be used. Therefore, we developed a novel image-based metric of daylighting in a virtual environment based on luminosity histogram analysis. In photography, a luminosity histogram is a graphical representation of pixel brightness within a digital image expressed by the tonal range of each pixel in units from 0 (darkest) to 255 (brightest) based on RGB (red, green, blue) channel brightness scale units (Nikon 2019). In the same context, luminosity can be hereby considered a lighting metric that qualitatively represents the brightness of a given scene. In such a case, the brightness mean value of an image would express its average relative luminance based on the average tonal value for all pixels in the image. Similarly, the standard deviation of brightness values expresses the discrepancies between pixel brightnesses and the mean value. Thus, a low standard deviation can suggest a low contrast in the image exposure (i.e. lighting) and vice versa. Research work by Inanici et al. has investigated luminance-based design metrics based on HDR images as a tool for predicting human visual comfort of lighting (Kumaragurubaran and Inanici 2013; Van Den Wymelenberg, Inanici, and Johnson 2010).