How to Choose the Right Light Bulbs

There are four main considerations that deter­mine whether a filament lamp (bulb) is suitable for a particular application - wattage, life rating, finish and cap fitting. You need to specify all four carefully when you are buying new lamps. 

The amount of energy a lamp uses is measured in watts. The light given off is roughly in proportion to the wattage. So, for example, a 150 watt lamp will produce roughly twice as much light as a 75 watt one of the same type. The amount of electricity used is directly proportionate to the lamp wattage; that means a 150 watt lamp will use twice as much electricity as the 75 watt one. 

Lamps (bulbs) can be clear or frosted. Clear lamps transmit the most light, giving brilliant iUumination. But they do create harsh shadows and so are most often used where a sparkling effect is desired, such as in a chandelier or inside enclosed fittings with opaque diffusers. 

Frosted lamps have internal finish that gives a more even light with more diffuse shadows and are therefore the most popular for general lighting use. 

A lamp should have a life of around 1,000 hours, subject to normal usage. Double-life lamps are intended to last for 2,000 hours, though there are fewer ratings to choose from -usually 40, 60, 100 and 150 watt. 

Filament lamps have an Edison screw fitting, with large and small sizes available. The most Common lamp is the familiar pear-shaped type, which comes in 15, 25, 40, 60, 75, 100 and 150 watt sizes and in both clear and frosted finishes. 

Colored lamps (bulbs)

Lamps are available in a range of different shades including pink, red, amber, yellow, blue and green. And they are usually rated at 15, 25, 40 and 60 watt. They have a poor light output for their wattage, with the darkest colors being the weakest. 

Globe (spherical) lamps have a frosted finish to enable them to be used without a shade. They come in several different sizes. The choice of rating is not so wide - 25, 40 and 60 watt in the smaller sizes, together with 100 and 150 watt in the larger ones. 

Candle lamps are available in plain and twisted versions. They are mainly used in candelabras and in some decorative wall fittings. Both shapes are generally obtainable in both clear and frosted finishes. 

Night lights are rated from 8 to 12 watts and provide continuous light at low cost for chil­dren's rooms and access areas where required. 

Reflector spots, which are used with spot­lights, come in two types - ISL and PAR. The former gives a soft-edged beam and is often used for spotlights, canlights (potlights) and uplighters. The ratings available are from 40 to 150 watt. PAR reflectors, which are more expensive, have a beam of exact width for highlighting specific objects. These come in 100 and 150 watt ratings. 

Tungsten tubes are used for lighting display cabinets, mirrors and other fittings and are available with single cap (3V2in long and 25 or 40 watt) or double cap (9 and 11in and 30 or 60 watt) in either a clear or frosted finish.

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