deliberate use of light to achieve practical or aesthetic effects
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Terms in this set (56)
rays that travel in a straight line until they encounter some objectlightsThe ratio of light absorbed by a material to the incident light falling on it. All materials absorb some light; darker objects absorb more than lighter-colored objects.absorptanceratio of light reflected by a surface to the incident light falling on itREFLECTANCE, REFLECTION FACTOR, OR REFLECTANCE COEFFICIENT2 combination of reflection1. specular reflection 2. diffuse reflection"regular reflection" (kind of reflection observed in a mirror) angle of reflection is equal to the angle of incident lightspecular reflectionThe reflected light is scattered in all directions so that the reflecting surface appears equally bright from any angle of view. Any surface with a sandpaper texture reflects light diffuselydiffuse reflectionratio of light transmitted through a material to the total incident light falling on it Light transmission may be either direct, diffuse, or a combinationTRANSMITTANCE, LUMINOUS TRANSMITTANCE, TRANSMISSION FACTOR, ORlight passes through clear, transparent materialsdirect transmissionlight is scattered evenly in all directions, appearing equally bright from any angle of view. Materials that transmit light in a diffuse pattern are known as translucent materials.diffuse transmissionbending of a ray of light as it passes obliquely through a materialrefractionan index of the intensity of light being emitted, transmitted or reflected from a surfacefootlambert (fl)A quantitative unit for measuring brightnessbrightness (luminance)effect of excessive brightness in the field of view, causing annoyance or discomfort andglaretrue or false: Brightness is the perceived light Luminance is a measured quantitytruethe brightness is from a surfacefootcandlethe illumination is on a surfacefootlambertThe surface on which the visual task is performed and at which the illumination is specified and measured.workplaneThe immediate contiguous area in which a worker performs visual tasks (desk, desk return, table that function as one task location, conference table shared by several workers)workstationA luminous source where light energy is generated and transmitted directly to a task.primary sourceSurfaces that derive their brightness from reflected incident illuminationsecondary sourceA generic term for artificial light sourcelampA complete lighting unit consisting of a lamp or lamps, together with parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to a power supply; referred to as a "fixture."luminairedevice for redirecting the radiant energy of a lamp by reflecting it in a desired directionreflectordevice for redirecting the radiant energy of a lamp in the desired direction by refraction through a lensrefractorthe ratio of light output (luminous flux) to the light produced by the lampefficiencythe ratio of output of luminous flux, expressed in lumens, to the power input in watts, expressed in "lumens per watt."efficacy3 types of lighting1. general lighting 2. task 3. accentincreases light levels over the work and immediate surroundings. Local lighting often allows the user to adjust and control lighting and provides flexibility for each user.taskprovides an area with overall illumination; provides fairly uniform lightinggeneral lightingDirectional lighting to emphasize a particular object or draw attention to a display item.accenta lighting source that closely replicates natural sunlight can be considered ______________natural light source4 different types of lighting fixtures1. direct 2. direct-indirect 3. indirect 4. shieldedtypes of light fixtures: distribute 90 to 100 percent of the light upwardindirecttypes of light fixtures: distribute light equally upward and downwarddirect-indirecttypes of light fixtures: Direct lighting tends to create shadows.directtypes of light fixtures: diffusers, lenses and louvers to cover bulbs from direct view to prevent glare and distribute lightshieldedtranslucent or semi-transparent (see-through) covers made of glass or plastic; bottom or sides of light fixtures to control brightnessdiffuserclear, transparent glass, plastic covers; incorporates prisms and flutes to distribute light in specific wayslensesbaffles that shield the bulb from view and reflect light; can be contoured to control light and decrease brightness. Parabolic louvers are specially shaped grids that concentrate and distribute light.louvers5 types lighting system1. direct 2. indirect light 3. semi direct 4. general diffuse 5. direct indirectmain source of light during daytimedaylightingWalls and ceiling must have a high-reflectance finish Room illumination is diffuse, shadowless, uniform, and with low glare Inefficient, since all of the useful light reaches the working plane only after a double reflection - within the fixture and off the ceilingINDIRECTMore efficient than indirect Allow higher levels of illumination without glare Employs a translucent diffusing element through which the downward component shines Ceiling is the principal radiating source, and the character of the room lighting is still diffuseSEMI INDIRECTThe minor upward component serves to illuminate the ceiling Shadowing in the space not a problem upward component is at least 25 percent and the ceiling reflectance is at least 70 percentSEMI-DIRECTFixtures distribute approximately an equal amount of light upward and downward Provide a bright ceiling and upper wall background for the luminaire General-diffuse fixtures (diffusing globe) emit light equally in all directions Direct-indirect fixtures have an open top, luminous side, and diffusing bottom Their light output has very little horizontal componentGENERAL-DIFFUSE AND DIRECT-INDIRECTInherently efficient; basically all light is directed downward Illumination of the ceiling is entirely due to light reflected from the floor and room furnishings Require a light, diffuse, high-reflectance floor, unless a dark ceiling is desired for aesthetic purposes Since illumination is largely independent of wall reflectance, walls may be any color.DIRECT