All of us have an idea of what brightness and luminescence is. However, sciences, disciplines, and industries measure it differently. How they measure it is relevant to their respective purpose and goals: how to increase the understanding of the phenomena and improve the lives depending on that understanding.
Candela, lux, and lumens are the ways we measure what we collectively but vaguely know as brightness. This article will discuss the three ways, and depending on the way, purpose, and goal, know which can be a matter of curiosity and which can be relevant and have practical use for our daily lives.
1. What is Candela?
The word candela comes from the Latin word for candle. According to a government institution, candela is the most human-oriented method for measuring light because it measures light as human vision perceives it.
The SI unit for candela is the basis for the science of measuring light, known as photometry. Because candela is the standard, most sciences and disciplines use candela to measure brightness. Disciplines as diverse as astronomy and photography employ candela.
Various industries, like those in electronics and communications, also use candela for measurement. The exact measurement of candela is monochromatic radiation with a frequency of 540×10 and a radiant intensity of 1/683 watts per steradian (unit of solid angle in SI).
The exact measurement provided by Candela has practical applications for things such as optic fibers, light bulbs, lighting in theater, automotive headlights, and illumination in buildings, factories, and other structures.
Though there are different ways of measurement, candela is always the defining yardstick.
2. What is Lux?
Meanwhile, lux is the amount of light that strikes a particular area. In scientific terms, it is the luminous flux (perceived power of light) per unit area. It sounds a bit complicated, but lux, to simply put it, is how bright a particular area is.
Lux has nothing to do with what the eyes see; instead, its primary concern is how much light a particular area receives, regardless of human vision or the presence of any observer.
The practical application of lux resides in the amount of light a particular area needs to receive for it to be efficient or for people working or doing things here to benefit or be efficient.
We measure it using the lux scale (lx), which measures about 1 lumen per square meter. The practical applications of lux are evident even to those of us who need to be more knowledgeable or have a pedestrian knowledge of science. A place or area that is too bright or has too little luminosity can affect people and things.
Remember, sunlight benefits our health, and knowing enough or too much sunlight can spell the difference between getting vitamin D or sunburn. We can say the same thing about lux. Having too much or too little can have an effect, and lux is how to know that. Lux has practical applications,
Foremost among them is illuminating almost all areas where there is human activity and where you use light: Streets and parks, coliseums and stadiums, theaters and cinemas, factories, schools, hospitals, and almost every place where you need illumination for various purposes.
However, since the measurement of lux depends on lumens, it is essential to know this final way of measuring brightness and luminescence.
3. What are lumens
Lumens, expressed as “lm”, is the total amount of light coming from a device. In common parlance, it answers how bright a device is. Scientifically, though, lumens is the expression used to measure luminous flux.
Though it answers how bright something is, lumens are less precise than candela. The reason is that candela always considers the direction of light, which, eventually, is a crucial factor for practical applications of light and brightness.
However, saying it is not as precise as candela does not mean it is an imprecise measurement. That is not the case. Lumens has always been measured against candela and is the unit of measurement for lux.
For this reason, the most rigorous of sciences and disciplines use candela. They need to be as precise and accurate as possible in relation to human eyesight. They must be exact to benefit from a particular light or brightness.
Meanwhile, we see lumens as an illustration of the brightness of specific objects, like light bulbs. It is not uncommon for us to see some manufacturers and companies advertise and sell their lights and other illuminations as having this or that number of lumens.
4. Why Knowing About Candela, Lux, and Lumens is Important
There is an exact science and mathematics underlying the interconnection of the three ways of measurement. It will be best to provide actual situations to illustrate their interconnection and how a basic understanding of them, even intuitively, impacts and affects our daily lives.
We must clarify that even though candela is the most human-oriented of the measurement of light, it is an exact measurement, as mentioned earlier. It is a light measurement having an exact radiant intensity and spectrum. For this reason, it is accurate and came to be known as the measuring stick.
The idea that candela must be the base measurement, the SI unit for measuring light, stems from the fact that humans, ultimately, are essential because we perceive light. Since we are always in a location, measuring light based on luminosity and direction makes much sense.
Imagine yourself using a smartphone. The light travels from the gadget to your eyes. The lights of the smartphones are too bright; you adjust them so that they will not irritate or damage your eyes. You do so because the light intensity is too much.
Candela’s practical applications stem from this understanding. Sciences and disciplines need to know the intensity of light to avoid damage to people and things and make it beneficial by generating just enough luminescence pointed toward a specific direction.
Knowledge of the intensity of light has practical applications in many sciences and disciplines, as mentioned already. Suffice it to say that there is such a thing as light intensity because brightness or light will be put or deployed in a particular direction, space, or locale, as well as to objects, things, and even humans.
The importance of knowing lux lies in the direction, space, or location that eventually will experience brightness, light, and luminescence. Knowing the luminous flux per unit area is fundamental for all lighting mechanisms anywhere.
You may not know the exact mathematics per se, but undoubtedly, you know whether an area is too dim or too light, and you need to adjust the lighting in that area. You may do this for health, safety, or aesthetics, such as watching TV, playing games, or doing something like reading or cooking.
Whatever the case, you intuitively understand lux and its importance. Based on that understanding, you will adjust light, illumination, and brightness accordingly. In that case, an area will receive the appropriate brightness.
You need to know how much light an area must receive and adjust accordingly. But how will you adjust? Going back to the smartphone, you adjust the light settings. If you are repairing your home or doing some furnishing, you will buy the appropriate lights or lamps.
Here, an intuitive understanding of lumens comes into play and is imperative. It is the light output you control that makes it beneficial and practical.
Knowing lumens is so essential. Industry players and government regulators of light bulbs and different types of lighting worldwide made it mandatory to label products to indicate how bright or powerful the light emits. Most devices state the number of lumens they have.
It has set the standards for luminosity in terms of lumens for particular devices illuminating certain locations and for specific purposes. Government and industry regulators do so to optimize and maximize the benefits of lighting while not being detrimental to the health and safety of people.
Having labels about the number of lumens a device emits is the source of confusion as to why most people regard lumens as the actual measure of brightness. However, if we understand the total light output of a particular device as brightness, the understanding may not be off the mark.
To summarize the interconnection of candela, lux, and lumens and to illustrate how our daily lives already imply an understanding of the interconnection of the three:
- You have a source emitting a total light output (light bulbs, fire, etc.). You measure the total light output in lumens.
- That light source illuminates a particular area or location (streets, parks, bedrooms, your eyes, etc.). You measure the light in an area in lux.
- Depending on many factors, the light intensity directed toward a particular area will differ (too bright, too dim, appropriate brightness, etc.). You measure the intensity of the light output in candela.
5. Final Thoughts
There are differing ways of measuring brightness because they have different applications. Candela is the base SI measurement for light because science considers human activity and brightness’ effects on everything to be paramount.
Meanwhile, lux has practical applications for illuminating areas. Lumens are essential because they indicate how much light a device emits despite effects, intensity, and location.
Knowing the interconnection of three measurements, even intuitively, you will know the appropriate brightness for health, safety, and aesthetic pleasure.
