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Saturday, April 28, 2012

How to select the type of light reflector for home

Electric (Artificial) Lighting

Lamp types
(1) Incandescent lamps produce a warm light,are inexpensive and easy to use but have limited lumination per watt (20 to 40) and a short life. Normal voltage lamps produce a point source of light. Most common shapes are A, R, and PAR. Low voltage lamps pro- duce a very small point of intense brightness that can be focused into a precise beam of light (for merchandise or art).These are usually PAR shapes or designed to fit into a parabolic reflector. Sizes are designated in 1⁄8 inch of the widest part of lamp.Tungsten-Halogen (quartz) and low voltage are a special type of incandescent. Quartz is another type of incandescent that has high-intensity white light with slightly longer life.

(2) Gaseous discharge lamps produce light by passing electricity through a gas. These lamps require a ballast to get the lamp started and then to control the current.

  1. Fluorescent lamps produce a wide, linear, diffuse light source that is well-suited to spreading light downward to the working surfaces of desks or displays in a commercial environment with normal ceiling heights (8′ to 12′). Lamps are typically 17, 25, or 32 watts. The deluxe lamps have good color-rendering characteristics and can be chosen to favor the cool (blue) or the warm (red) end of the spectrum. Dimmers for fluorescent are expensive. Fluorescent lamps produce more light per watt of energy (70–85 lumens/watt) than incandescent; thus operating costs are low.The purchase price and length of life of fluorescent lamps are greater than for incandescent and less than for HID. Four-feet lamp lengths utilize 40 watts and are most common. Designations are F followed by wattage, shape, size, color, and a form factor.
  2. High-intensity discharge (HID) lamps can be focused into a fairly good beam of light. These lamps, matched with an appropriate fixture are well-suited to beaming light down to the working place from a high ceiling (12′ to 20′).Dimming HID lamps is difficult. The lamps are expensive but produce a lot of light and last a long time. If there is a power interruption, HID lamps will go out and cannot come on again for about 10 minutes while they cool down.Therefore,in an installation of HID lamps, a few incandescent or fluorescent lamps are needed to provide backup lighting. Since they operate at high temperatures, they would be a poor choice for low ceilings, wall sconces, or any other close proximity light source. They would also be a poor choice in assemblies and other occupancy where power outages could cause panic. Mercury vapor (MV; the bluish street lamps). Because they emit a blue-green light, they are excellent for highlighting foliage, green copper exteriors, and certain signage. Deluxe version is warmer. 35 to 65 lumens/watt. This is not much used anymore. Metal halide (MH) are often ice blue cool industrial-looking lamps. Deluxe color rendering bulbs are 50 to 400 watts, and almost as good as deluxe fluorescent for a warmer effect. Efficiency is 80 lumens/watt. High-pressure sodium (HPS) produces a warm golden yellow light often used for highways. Bulbs are 35 to 400 watts. Deluxe color rendering is almost as cool as deluxe fluorescent for a cooler effect. Efficiency is 100 lumens/watt. Low-pressure sodium (LPS) produces a yellow color which makes all colors appear in shades of grey. They are excellent for promoting plant growth indoors. Bulbs are typically 35 to 180 watts. Used for parking lots and roadways. Efficiency is 150 lumens/watt.
  3. Cold cathode (neon) has a color dependent on the gas and the color of the tube. Can be most any color. Does not give off enough light for detailed visual tasks, but does give off enough light for attracting attention, indoors or out.

Types of reflectors

Common types of reflectors

Lighting systems and fixture types

Note: Costs include lamps, fixture, and installation labor, but not general wiring. As a rule of thumb, fixtures are 20% to 30%, and distribution (not included in following costs) is 30% to 70%.

(1) General room lighting; A large proportion of commercial space requires even illumination on the workplace.This can be done a number of ways.

  1. Direct lighting is the most common form of general room lighting.
  2. Semidirect lighting; All systems other than direct ones necessarily imply that the lighting fixtures are in the space, whether pendant-mounted, surface-mounted, or portable. A semidirect system will provide good illumination on horizontal surfaces, with moderate general brightness.
  3. General diffuse lighting; A general diffuse system most typically consists of suspended fixtures, with predominantly translucent surfaces on all sides.Can be incandescent,fluorescent,or HID.
  4. Direct-indirect lighting; A direct-indirect will tend to equally emphasize the upper and lower horizontal planes in a space (i.e.,the ceiling and floor). Typical fixture:same as semidirect.
  5. Semi-indirect lighting; A semi-indirect system will place the emphasis on the ceiling, with some downward or outward-directed light.
  6. Indirect lighting; A fully indirect system will bounce all the light off the ceiling, resulting in a lowcontrast environment with little shadow. Typical fixture:Same as Direct-Indirect.
  7. Accent or specialty lighting; Used for special effects or spot lighting, such as lighting art objects or products on display.

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