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Pupil Lumens and Their Impact on Lighting

Pupil Lumens and Their Impact on Lighting

  • Ashby Maxim

The way we perceive and measure light is contingent on many factors. In most cases, lighting efficacy relies on analyzing the illuminance properties of the light itself. However, the way our eyes react to light is just as important to consider in the lighting industry.

Traditional Measurements in the Lighting Industry

Descriptors such as foot-candles, lumens, color rendering index, and correlated color temperature are some of the most common ways to describe and define how much light is necessary for a given task or location. Foot-candles and lumens both measure the illuminance or quantity of visible light available. Meanwhile, the color rendering index refers to the light source’s ability to portray color accurately. Correlated color temperature measures the hue a light produces. These four measurements are vastly popular in describing the efficacy of a light source based on its illuminance and the colors that can impact how we perceive objects in the light.

How Our Vision Impacts Light

The previously described measurements of light aren’t always good options. For example, a light may have a high lumen count with a yellow or grey color. While this light is bright enough to illuminate the area, it may still be hard for the eye to make out fine details because of the way the lumens and colors or hues affect our vision. 

The overall quality of our vision depends on many lighting factors. A few of these include: 

  • Light intensity
  • Light distribution 
  • Color 
  • Contrast
  • Reflection
  • Glare
  • Air quality
  • Motion of subjects
  • The viewer

How Our Eyes Perceive Light

Our eyes utilize two types of photoreceptors: cones and rods. Cones typically handle daytime vision because they control the perception of colors such as red, green, and blue in high lighting conditions. Cones are also responsible for depicting fine detail in bright lights. Conversely, rods most commonly handle nighttime vision or sight in low lighting situations. 

To perceive light in bright situations, the pupil contracts to increase the detail, depth of field, and brightness. For low light, our eyes dilate to let in more light. In the case of light output, photopic lumens describe the amount of light that the eye’s cones register in high lighting situations. Scotopic lumens are the amount of light that the rods record in the eyes.

The Importance of Scotopic Lumens

While standard foot-candles and lumens can measure the amount of photopic lumen output of a light source, they cannot measure scotopic lumen output. Scotopic lumens are just as crucial as photopic lumens, if not more important. For example, smaller pupils increase visual acuity and reduce glare and headaches associated with bright lighting. Because rods control the pupil’s opening and closing, the perception of a room’s brightness is primarily reliant on rods and scotopic lumens. These examples highlight how crucial it is that lighting manufacturers consider scotopic lumen calculations when marketing to consumers. This is where the concept of pupil lumens comes into play.

Pupil Lumens and Their Impact on Lighting

Pupil lumens measure the light that stimulates the rods in the eyes to determine scotopic lumen output and the total visually effective number of lumens. One can calculate the pupil lumens by multiplying the photopic lumens by the scotopic/photopic value (S/P). The S/P value is the number that describes the ratio of scotopic to photopic quantities of a light source. Consumers should always look for a light source with an S/P of at least one. A ratio of one means the light source performs equally as sufficient under scotopic (low light) and photopic (bright light) conditions. The higher the rate, the better your eye will perform under the light source.

The Benefits of Pupil Lumens

In the lighting industry, efficiency is vital. Light sources should be energy-efficient, cost-effective, and provide ample lighting in various situations. 

To make energy-efficient, high-quality light that promotes clear vision, it’s necessary to consider how the eye adapts to light. Otherwise, lighting companies risk creating high-intensity lights that require loads of energy and have little to no effect since the human eye will not perceive it as a more precise lighting solution.

By considering the pupil lumens a light source offers, it is possible to use less wattage to illuminate a space by designing light sources that stimulate both the rods and cones in the human eye. By using less wattage, less energy is necessary, which makes the light source eco-friendlier. 

In most instances—such as LED light sources, which already have lower energy consumption rates—considering pupil lumens will not only reduce the necessary energy, but it will also decrease cost and improve the lighting conditions. With less wattage, the consumer spends less money on electricity bills. For business owners using LED commercial light fixtures with a high pupil lumen measurement, this can result in serious monthly savings. Additionally, light fixtures will be more effective in depicting accurate portrayals of light and objects when taking pupil lumens into account. 

In commercial settings, such as warehouse facilities and factories, this can be extremely useful. The ability for employees to see small details without additional effort can increase worker efficiency as well as safety. Many business owners may overlook the importance of ample lighting or be unaware of pupil lumens’ importance. By providing the best light sources, owners offer their employees the opportunity to achieve tremendous success in their roles. The better the pupil lumen measurement of the lights they choose to use, the better the lighting source will be for employees. 

Pupil lumens and their impact on lighting are often an overlooked topic in the lighting industry. Most average consumers are unaware of the importance of pupil lumens, especially with so many other terms in the industry that describe the color and luminosity of light fixtures. But the way our eyes perceive light is just as important to consider when calculating the efficacy of a light source. No matter how bright or dim the light is, the luminosity does not matter unless one accounts for the human eye’s perception at the same time. Check out our offerings at Eco LED Mart for the best LED lighting options with ample pupil lumens for any task.

Pupil Lumens and Their Impact on Lighting

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