Lamps used in stage and studio applications are mainly of the tungsten halogen or discharge types. Within each of these categories there are numerous variations in lamp design. The most obvious variations are the ones we can easily see by looking at the lamp such as the type of lamp base or end cap, and whether the lamp is single ended or double ended. A less obvious variation is the filament design. Variations we cannot see include the colour temperature, luminous efficacy and rated life hours. To obtain detailed information for any particular lamp type is is necessary to refer to the lamp manufacturer's product catalogues.
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Tungsten Halogen Tungsten Halogen lamps, like all incandescent lamps, produce light by passing an electric current through a fine tungsten filament causing the filament to glow white hot and thus produce visible light. Incandescent lamps burn out because the filament is gradually depleted as tungsten molecules boil off and are deposited onto the inside of the envelope, causing it to blacken, until the ever weakening filament eventually breaks. In halogen lamps a small amount of a halogen gas is added to the gas mix in the envelope. The halogen gas interacts with the tungsten molecules causing them to be re-deposited onto the filament, in a process known as the halogen cycle, greatly increasing the lamp life. The lamp envelope is made of quartz to withstand the high temperature and pressure required for the halogen cycle to operate. Halogen lamps produce approximately 30% more light than ordinary lamps of the same wattage. |
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Discharge Lamps Discharge lamps have no filament, instead they produce light by passing an electric current through the gas inside a glass, quartz, or translucent ceramic arc tube ionizing the gas in the process. The high intensity light produced is usually either visible, ultraviolet (UV), or a combination of both. The color of the light depends on the mixture of gases and other materials inside the arc tube as well as the gas pressure and amount of electric current. Some lamp types include a phosphor coating inside the envelope to convert UV light into visible light. Discharge lamps require a ballast device and are more difficult to control than tungsten halogen lamps. They typically take a few minutes to warm up before producing their full light output and if switched off may require a cool down period of several minutes before they can be restarted. Their high output makes discharge lamps especially useful for projectors and followspots. |
Luminaire manufacturers take considerable care to match their optical system designs to the most suitable lamp types. In some cases luminaires are designed to allow the use of several different lamp types so the luminaires can be closely matched to the users application. To get the best performance from your luminaires always choose high quality lamps of the correct types.