The light terms explained
Lumen, lux and candela: If you are involved with lighting, you will probably have heard these terms before. However, when you are not a specialist, these terms can be somewhat confusing. These light terms are used to measure light with different dimensions.
In this blog, you will read about the differences between lumen, lux and candela and why it is important to know these differences.
When talking about the unit lumen, this refers to the total luminous flux within a beam of light. To compare two light sources, it is best to use lumens instead of watts.
In fact, two lamps of the same wattage can differ greatly in light output. For example, an 8W LED bulb gives significantly more light than, say, an 8W halogen bulb. With Led lighting, such as our downlights, the lumen/Watt ratio is very high.
The photometric unit lumen determines how the human eye experiences light. So the color of the light also plays a role in determining the total luminous flux in lumens.
A 1 watt green light source (550nm) will emit about 640 lumens while an orange light source (650nm) will emit only 73 lumens.
So look not only at the wattage of an LED bulb, but also at the color of the bulb.
Lux measures illuminance per square meter. When a light beam of 1 lumen falls on a 1-meter plane, the illuminance is 1 lux. Thus, 1 lux is equal to 1 lumen per square meter.
So Lux and lumen differ because lux takes into account the area over which the light is spread. Thus, the amount of lux depends on both the light source and the surface.
So if you use a 2000 lumen light source and spread it over 1 m2, this room will be illuminated with 2000 lux. However, as soon as this light source shines on an area of 20 m2, the area will be illuminated with 200 lux.
Candela is the Latin word for “candle. Logically, then, 1 candela corresponds to the luminosity of 1 standard candle. This unit is considered the standard for measuring light intensity and dates back to the time when artificial light was unknown.
Today, candela is still used as a unit for measuring light intensity. For example, an ordinary flashlight has a brightness of about 1 candela and a 100-watt incandescent lamp has about 120 candela.
Officially, candela is defined as follows:
“The candela is the luminous intensity in a given direction of a source emitting monochromatic rays at a frequency of 540 x1012 Hz and whose irradiance in that direction is 1/683 watts per steradian.”
Source: nist.gov
The terms lux, lumen and candela are widely used during lighting projects. We hope that with this blog we have given you more clarity on these lighting terms for your next lighting project.
Are you interested in lighting for your space? Please feel free to get in touch!
Partner with Clearlight to achieve the highest possible returns? Fill out the contact form and you will receive a call within 2 business days
