Aquarium LED Lighting Terms: Part 1
Posted By: Matt Allen
LED lighting is becoming more and more popular for lighting home aquariums and offers many benefits over traditional, fluorescent aquarium lighting. The benefits include higher efficiency, longer lifespan, lower heat production, more light control, and more customization. Because LEDs are such a unique lighting technology, the terms used to describe and compare light fixtures can be overwhelming. This week we will begin a 3 part series of posts discussing common lighting terms used to describe LED light fixtures, their performance, and how it pertains to the aquarium hobby.
The first two lighting terms we will dive into are Lumen and Lux.
Lumen: the SI unit of luminous flux, a measurement of the total amount of visible light emitted (light output) from a light source in all directions. There are two important things to remember when reviewing lumen output of any aquarium light fixture. First, luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light. This means wavelengths of light the human eye is more sensitive to (greens and yellows) are “weighed” more heavily than those our eye is less sensitive to. Although lumens are a good measurement of visible light we perceive, they may under-represent wavelengths of light that have other benefits in our aquariums, like those used for photosynthesis. Secondly, although lumens accurately measure total light output, they do not tell us anything about how well the light fixture does at directing that light to where it is needed. All the lumen output in the world does not help us unless it is being properly directed to where it is needed.
Lux: the SI unit of illuminance which is equal to 1 lumen per square meter, can also be considered luminous flux density. Lux is a measure of how well a surface at a given distance from the light source is illuminated (light intensity). Measuring lux or reviewing lux data at various distances from the light fixture will tell you how well the fixture directs the lumens it is producing into the target area. In our situation the target area would be the footprint of our home aquarium. Design features including the shape of the light fixture, distribution of the LEDs, and any secondary optics or reflectors the fixture uses will all impact lux measurements.
Next week we will discuss PAR (Photosynthetically Active Radiation), PPFD (Photosynthetic Photon Flux Density), and the concept of photosynthetically usable radiation as it pertains to the quality of light produced by an LED light fixture.
View our collection of aquarium LED lighting.