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Brightness
subjective sensation that occurs in conciousness of a human behavior
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Luminance
objective measurement of intensity per unit of projected area
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Luminaire (lighting fixture)
emits light downward, upward, or multidirectional and concentrated or diffuse
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Glare
is a bright light which can interfere with visual perception
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Diffuse Light
a distribution of light that is dispersed in a wide pattern and not incident from any particular direction
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Direct/Indirect
light emitted in a downward and upward direction, with little or no light emitted at angles near the horizontal
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Cutoff
measured up from the nadir (straight down 0 degree angle), the angle of the first line of sight at which the care light source is not visible
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Downlight
a recessed surface mounted, or pendant-mounted luminaire which emits light in a downward direction with no upward component
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Indirect
an upward distribution of light which produces illumination on the horizontal workplane via reflection from the ceiling and upper walls
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Grazing Light
from luminaires located close to a surface being lighted, strengthens highlight and shadows
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What is grazing light used for?
inspection to detect surface blemishes and errors in workmanship
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What is grazing light appropriate for?
lighting heavily textured surfaces such as rough plaster, masonry, or concrete; disastrous for flat walls of smooth plaster or gypsum board
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Visual Comfort Probability
rating is defined as the percentage of people who, if seated in the least desirable location in an office work space, will find a lighting installation comfortable.
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Reflected Glare
excessive uncontrolled luminance reflected from objecs or surfaces in the field of view
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Two additional lighting problems that cause concern for VDT users:
- 1) proper lighting for the non-VDT tasks the worker must also perform
- 2) lighting of the area in the worker's field of view
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