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In the world of lighting, there are several specific terms that are recognized as units of light measurement. Each of the terms has a different meaning and acts as a different capacity for measuring the amount of light put out by a specific source and the intensity of that light. Light, much like sound, travels in wavelengths. Each color has its own wavelength and is characterized by a specific type of light. For example, red light has the lowest frequency wavelength, making it the most difficult to see from a distance. Conversely, blue light has a long wavelength, which allows the color to easily be seen from a distance. Look to these common terms of light measurement to understand the unique principle that is lighting.
The first term of light measurement is candela. Taken from the root word candle, a candela is a measurement unit the rates the intensity of light. In addition to identifying the specific intensity of light, a candela also takes the direction of the light source into account. The name originated by the source of the first usable lighting device, the candle. For this reason, the formula for measuring a candela is based on this rather historic method of lighting. However, the new standard for a candela is based on the glow measured from molten hot platinum, allowing this light measurement to venture into the modern age. A common term that is often associated with light measurement is the Watt. However, the Watt, named after famed inventor James Watt, is a measurement of energy. So the number you see listed on light bulbs that is followed by the unit Watt is actually a measurement of the energy that specific bulb is capable of using instead of the amount of light that bulb is capable of emitting. However, since Watts are generally the basis for energy units, they are often included in the mathematical equations for other units of light measurement. A more historic unit of light measurement is the footcandle. This unique unit was first used to determine the amount of light shed by a standard candle. Since all candles were hand made (and most were homemade), this measurement often varied depending on the specific candle used. Even though you may have ten different candles from the same batch, you will have ten different measurements for a footcandle due to these inaccuracies. Today, footcandles are the main light measurement for stage lighting, photography, and architecture. Finally, one of the most widely used units of light measurement is the lumen. The lumen is a measurement of the flow of light instead of the intensity of light. Just like waves in water, light waves tend to ebb and flow, allowing the creation of wavelengths. When a lumen rating is given to a lamp, then that unit signifies the total amount of light produced by that specific fixture. As previously mentioned, the Watt plays a role in this equation, since that is the amount of available energy used to create the light. The lumen production in light bulbs and light fixtures can decrease over time, so generally the amount listed on a fixture is the maximum light measurement possible. |
Lighting Types and Bulbs