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When appearing on light bulb packages, brightness means luminous flux, while in other contexts it means luminance. [5] Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky.
Brightness, the subjective perception elicited by the luminance of a source; Luminance, the photometric equivalent of radiance (lm·sr −1 ·m −2) Photometry (optics), measurement of light, in terms of its perceived brightness to the human eye; Radiometry, measurement of light, in absolute power units; Luminosity
As an example, if one uses a lens to form an image that is smaller than the source object, the luminous power is concentrated into a smaller area, meaning that the illuminance is higher at the image. The light at the image plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens.
The difference between brightness and lightness is that the brightness is the intensity of the object independent of the light source. Lightness is the brightness of the object in respect to the light reflecting on it. This is important because the Helmholtz–Kohlrausch effect is a measure of the ratio between the two. [3]
Standard SMPTE cinema screen luminance [10] 80 cd/m 2: Monitor white in the sRGB reference viewing environment 250 cd/m 2: Peak luminance of a typical LCD monitor [11] [12] 700 cd/m 2: Typical photographic scene on overcast day [7] [9] [12] 10 3: kcd/m 2: 1 kcd/m 2: Cloudy sky at noon [4] [12] 2 kcd/m 2: Average cloudy sky [5] [12] 2.5 kcd/m 2 ...
For example, examine the following images of a fire breather (fig. 1). The original is in the sRGB color space. CIELAB is a perceptually uniform lightness prediction that is derived from luminance , but discards the and , of the CIE XYZ color space. Notice this appears similar in perceived lightness to the original color image.
In contrast, the term brightness in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to ...
Contrast is the difference in luminance or color that makes an object (or its representation in an image or display) visible against a background of different luminance or color. [1] The human visual system is more sensitive to contrast than to absolute luminance; thus, we can perceive the world similarly despite significant changes in ...