For most applications, lamps can be divided into three categories: incandescent, fluorescent and high intensity discharge.

• tungsten standard lamps

• tungsten halogen lamps

Where used: widespread applications where intended hours of use are low.

Strengths

1. Low initial cost.

2. Excellent colour rendition.

3. Inexpensive dimming capability.

4. Simple to operate and install.

1. Relatively short useful life with poor over-voltage tolerance.

2. Very inefficient source of light. On average, less than 10% of the wattage goes to produce light; the remainder becomes heat.

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• linear fluorescent lamps

• compact fluorescent lamps

• induction lamps

Where used: spaces that require cool white and warm white lamps to provide acceptable colour.

1. More efficient than incandescent.

2. Low heat generation.

1. Can require a relatively expensive fixture.

2. Magnetic ballasts in fluorescent fixtures can have an objectionable hum, go for electronic ballasts as in new CFL's.

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• high pressure sodium

• low pressure sodium

• metal halide

• mercury vapour

Where used: security lighting, street lighting, industrial installations, office installations and shop displays.

1. New generation metal halide lamps have good colour rendition.

2. More efficient than incandescent.

3. Long lamp life.

1. Sodium vapour lamps have a yellow light that can distort colour.

2. Takes from five to 10 minutes to reach full light output.

3. Can be costly to install.