Ever noticed the label of your bulb carefully? You may have noted that its light output is displayed in something called ‘lumens’.
Lumen vs ANSI Lumen
The difference between lumen and ANSI lumen is that ANSI lumen is standardized by the American National Standards Institute and is more specific and accurate than the lumen which is standardized by the International System of Units.
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Lumen (lm) is the SI unit for measurement of luminous flux i.e. the intensity (in candela) of light emitted per solid angle. ANSI lumen is also used to measure luminous flux but is standardized by the American National Standards Institute.
The reason for introducing a new unit in the form of ANSI lumens is that it usually provides a more realistic brightness measurement since it is well structured and based on a greater number of experimental values.
Comparison Table
| Parameter of Comparison | Lumen | ANSI Lumen |
|---|---|---|
| Symbol | The symbol for lumen is ‘lm’ | ANSI lumen does not have any specific symbol |
| System of units | Lumen is the unit of luminous flux under the SI system of units | ANSI lumen is not an SI unit for measuring luminous intensity |
| Standardization | It is not standardized by ANSI | It is standardized by the American National Standards Institute |
| Accuracy | It is less specific and accurate than ANSI lumen | It is more specific and accurate than lumen since it is based on greater no. of experimental values |
| Applications | It is used for rating lamps and light bulbs | It is used for displaying the light output of projectors |
What is Lumen?
Lumen s derived from the Latin word lumin meaning light. It is the standard unit used for measuring the amount of light intensity across a solid angle of one steradian i.e. it measures luminous flux. Its symbol is ‘lm’.
1 lm = 1 cd x sr
(cd-calendula: SI unit to measure light intensity
sr-steradian: SI unit to measure solid angle)
Since 2010, lighting equipment is labelled primarily in terms of luminous flux (in lumens, lm) as an alternative to electrical power (in watts, W).
The more is the lux (for constant lumens), the farther is the reach of the light from the source. On the other hand, more are the lumens (for constant lux), more is the brightness of light through a given area.
What is ANSI Lumen?
ANSI Lumens another unit for measuring luminous flux, and is assigned by ANSI-American National Standards Institute but I, not an SI unit. It finds applications majorly in the rating of projectors.
For commercial purposes, the projectors that undergo this procedure have their luminous flux quoted in ANSI lumens.
Method for measuring ANSI lumens for projectors: The light output of the projector is recorded at nine points around the screen and then its average is calculated.
The product of the average value with the area of the screen gives the brightness of the projector in ANSI lumens. The specification for the ANSI lumen measurement of projectors does not depend on the size of the image that is projected.
Major Differences Between Lumen and ANSI Lumen
- Lumen is the SI unit for the measurement of luminous flux to rate the light output of an artificial source of light, Whereas ANSI lumen is not an SI unit.
- ANSI lumen is described and structured by the American National Standards System which also has a specific procedure to measure the luminous flux but lumen is not standardized by the ANSI
- https://iopscience.iop.org/article/10.1088/0026-1394/11/3/001/meta
- https://www.spiedigitallibrary.org/conference-proceedings-of-spie/2650/0000/New-ANSIIEC-standard-for-projectors/10.1117/12.237015.short
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
