(6) Light Distribution and Glare & Principles of Lighting Design Flashcards
excessive brightness in the field of vision that causes discomfort or, in extreme cases, produces a disability from a temporary loss of vision
glare
a rating of a lighting installation expressed as a percentage of individuals who, when viewing from a specified location and in a specified direction, will be expected to find it acceptable in terms of discomfort glare
visual comfort probability (VCP)
typically made from clear UV-stabilized plastics
lenses
slats in a light fixture that create openings for emitting light
louvers
opaque or translucent elements that shield a light source from direct view
baffles
formula for the average illuminance
E = lm/A
formula for the illuminance from a single point source
E = l/d^2
formula for the illuminance for the cosine Law of Incidence
E = (l/d^2)cosϴ
the currently accepted method for calculating average illuminance levels for indoor areas unless the light distribution is extremely asymmetric
zonal cavity method
the product of all considered factors that contribute to a lighting installation’s reduced light output over a period of time
light loss factor
the quantity of lamps found in the specified or existing luminaire
number of lamps in luminaire (N)
the minimum required or the given number of luminaires in the space
number of luminaires (#)
the ratio of the amount of light (lumens) illuminating the work plane to the output of the lamp(s) in a fixture; a number indicating cavity proportions from length, width, and height
coefficient of utilization (CU)
an approximate maximum spacing-to-mounting height ratio required to ensure uniform illumination on the work plane
S≤(CS x MH)
spacing criterion (CS) ratio
the power consumed for illumination (W) divided by the area served by the lighting installation; it is expressed in W/sq. ft or W/sq.m
unit power density (UPD)
