Some light meters are specially designed to measure the intensity of a light source in lux.
Like most natural phenomenon, light can be measured in various units. One unit, called lux, is a measurement of the amount of light a light source gives off based on the space it illuminates in square meters. While a seemingly convoluted measurement, many lighting data sheets give illumination values in lux and the measurement is often used in the field when the absolute amount of light produced, rather than the relative amount, must be obtained. This is especially useful in scientific processes, where this measurement is most often used.
Instructions
1. Turn on your light meter.
2. Test your light meter with a calibrated light source, if possible. A calibrated light source is a light source of known brightnesses that can be used to test the accuracy of your light meter. While modern digital light meters rarely drift in their readings, as older analog models were prone to do, it is still advisable to check one's equipment before proceeding.
3. Set your light meter to measure the amount of light in lux. This is done differently on each light meter and not all light meters can measure light in lux, so make sure your meter is capable of doing this. For specific instructions, consult your meter's instruction manual.
4. Turn the knob on the lux meter to 2,000. This is the maximum lux value the meter will measure and the lighting of most places will fall below 2,000 lux. If you are measuring an extremely bright source, such as a computer scanner, turn the knob to 20,000 lux. Especially dim sources, like candlelight, can be measured with the lux meter set to 200.
5. Take four to five lux measurements of the space or light source that you are measuring. When doing this, hold the meter at waist level and point it towards and area of even illumination. If your values differ widely, take more measurements and use either the mean (average) or mode -- most frequent reading given -- as your general lux reading.
6. Use the set of readings, their average or their mode to determine if the space you are measuring is over-lit or under-lit, according to your requirements.
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