Introduction
Are you in the market to add some lighting to a new project and in doing so, run into some different lighting ratings that are a bit foreign? You’re not alone here. When it comes to lighting, there are various units of measurements to describe the light intensity of a given lighting source such as foot-candle, lumen and lux.
Understandably, if you’re new to lighting, these terms can be confusing. On top of this, understanding when a given unit of measurement is appropriate over another requires a fundamental understanding of these uses and the slight differences in what they represent.
In this article we will provide a top-down explanation of foot-candles versus lumen output, discuss the scenarios in which they are appropriate for use and provide some guidance as you approach those lighting projects!
Lumen Output
By Definition a Lumen is an SI unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle of one steradian from a uniform source of one candela. Without turning this into a physics discussion, the importance of a lumen in regards to lighting is it’s a measurement of the light emitted from a lighting fixture.
Why is this important? Well, what lumens don’t take into consideration is how that light is dispersed from a lighting fixture. Imagine a fixture has a standard lumen output, but the light is shining through a dark amorphous glass enclosure. In this example the light fixture may be giving off a great deal of light, but we wouldn’t know it because of how the light is limited by the dark glass enclosure. See the issue here? You could be buying a light fixture that has a high lumen rating, but doesn’t actually provide a good light source due to how the lighting fixture is encased. This is where foort-candles come into play.
Foot-Candles
Foot-candles by definition are a unit of illumination (now little used) equal to that given by a source of one candela at a distance of one foot (equivalent to one lumen per square foot or 10.764 lux). Okay, so what’s the difference here? The importance here is that foot-candles give insight into how bright a light source is perceived, hence the ‘per lumen per foot’. So foot-candles will not necessarily give insight into the intensity of the light but how that light will actually illuminate a space. This is a critical differentiator in how lumen output and foot-candles are different in the information they provide.
Next Steps
Hopefully this article has helped clear up some of the confusion around these common lighting units of measurement. If you’re in the early stages of a new lighting project and you could benefit from working with a trusted lighting supplier in the space we here at Energy Avenue would love to help. We have a full staff of knowledgeable lighting professionals that would be happy to help you with that project! Contact us today, to learn more about how we can help!
