When selecting lighting solutions, one of the most important factors to consider is luminous flux. But what exactly is luminous flux, and how does it impact your lighting choices? In this blog, we’ll explore the concept of luminous flux, how it relates to the brightness of light sources, and its importance in lighting design. Whether you’re a lighting professional or just curious about lighting technology, understanding luminous flux can help you make informed decisions about your lighting needs.
Luminous flux is a measure of the total amount of visible light emitted by a light source, typically expressed in lumens (lm). It quantifies how much light is perceived by the human eye, considering the varying sensitivity of the eye to different wavelengths of light. While light sources can emit radiation across a broad spectrum (including ultraviolet and infrared), luminous flux only relates to the visible spectrum that the human eye can detect. This means that wavelengths outside the visible spectrum, such as UV and infrared radiation, are not considered in the calculation of luminous flux.
Unlike total radiant power, which measures all electromagnetic radiation emitted by a light source, luminous flux focuses only on the light that is visible to humans. The human eye is more sensitive to certain wavelengths, particularly those in the green-yellow part of the spectrum, and less sensitive to red and blue. This is why luminous flux accounts for the photopic response of the eye, giving a more accurate representation of how bright a light source appears.
In physics, luminous flux is defined in relation to the amount of light produced by 1 watt of radiated power at the wavelength of green light (555 nm). Under these conditions, 1 watt of radiated power at 555 nm corresponds to 683 lumens. However, since the human eye is more sensitive to some wavelengths than others, the relationship between watts of radiated power and lumens varies depending on the wavelength. For example, light at 555 nm will appear brighter to the human eye than light at 455 nm (blue) or 755 nm (red), even if both emit the same amount of energy.
In everyday terms, when we talk about the “lumen output” or “lumen package” of a light source, we’re referring to the luminous flux. Essentially, it’s a way to ask, “How much light does this light fixture produce?” You can think of this in the same way you might ask, “How much heat does my central heating system produce?” The answer to the heating question is in kilowatts (kW) or BTUs, and for lighting, the equivalent answer is in lumens.
In the world of LEDs, LM-80 testing is an important process to determine the long-term performance of LEDs. The test measures the luminous flux over time to assess how much light output a particular LED will provide after extended use. Initially, luminous flux is measured as 100%, denoted as L100, which represents the light output at the start of the test.
As the LED continues to operate, the luminous flux gradually decreases—a process known as lumen depreciation. This decline is usually measured over long periods, such as 6,000 to 10,000 hours. After this time, the LED may still function, but its luminous flux will have decreased to L90 or L80 (i.e., 90% or 80% of its original light output). Temperature plays a critical role in lumen depreciation, and LEDs that are kept cooler tend to maintain their luminous flux better over time.
The decline in luminous flux is gradual, and unless a light fixture experiences a component failure (like the driver), the light output will typically decrease at a slow pace. This is a significant difference from traditional lighting technologies like fluorescent or HID lamps, which tend to experience more abrupt failure. For LEDs, manufacturers often talk about the rated life as the point when the luminous flux drops to L70, meaning the light output is reduced to 70% of its initial value. The rated life typically refers to the time it takes for an LED to reach this point.
At ACE LED Light, we understand the importance of luminous flux in lighting design. Our products are engineered to provide high-quality, energy-efficient lighting solutions that meet the demanding needs of industrial environments. From our LED high bay lights to our LED area lights, LED tri-proof lights, and LED street lights, we prioritize luminous flux to ensure our customers receive the brightest, most reliable lighting for their spaces.
By offering luminous flux ratings that meet your specific needs, we help ensure that every installation maximizes energy savings, enhances productivity, and provides safety in industrial, commercial, and outdoor environments. Our commitment to high-performance LED solutions makes us a trusted leader in the lighting industry.
