Candela vs Lux vs Lumens

Picture this: You’re standing in the middle of the lighting aisle, eager to find the perfect bulb to illuminate your home. You pick up one, then another, and another. But instead of the straightforward brightness levels you were expecting, you’re met with terms that sound like they’ve been plucked from a physics textbook: candela, lux, lumens. You scratch your head, wondering why can’t there be a universal language for light? Well, as it turns out, each term has its unique story and purpose in the world of illumination. Before you throw in the towel, let’s embark on a journey to decode these terms and shed some light on the mysteries of lighting measurements.

Understanding the Basics

Candela (cd)

Light plays a pivotal role in our lives, and when we discuss its brightness, the term “candela” often comes into play. Picture yourself holding a candle in a dim room. The gentle radiance it casts is a basic representation of “candela.” Often dubbed as “candlepower,” candela measures the brightness of a light source in a specific direction, much like the focused glow of that candle you’re holding. Represented by the symbol “cd,” it’s the official SI unit (International System of Units) for quantifying light’s intensity in a given direction.

The name “candela” finds its origin in the Latin word for candle. Historically, the brightness of a standard candle was the benchmark. To give you a clearer idea, a typical candle emits light with an intensity close to “1 cd” in all directions.

So, why is this metric crucial? Candela offers insights into how distant we can be from a light source and still discern its brightness. Consider the piercing beam of a laser pointer or a spotlight; their intense focus in one direction grants them a high candela rating.

Modern interpretations have further honed this concept. For example, a standard 30-watt fluorescent bulb radiates approximately 165 cd uniformly. Yet, when you channel that light into a concentrated 20° beam, its intensity soars to an impressive ~21,000 cd. The bottom line? A more focused light beam results in a higher candela value.

In a nutshell, a lofty candela figure signals a more luminous light, particularly when directed in a specific path.

Lumens (lm)

In today’s world, when you’re looking at light bulbs, “lumens” is the term you’ll encounter most often. It represents the luminous flux, which in simpler terms, is the total amount of visible light emitted by a source. Essentially, the lumen rating tells you how bright a light source is. The higher the lumens, the brighter the bulb. The term “lumens” steps into the spotlight when we talk about the total amount of visible light a source emits. Picture a fountain in a park, gushing water in all directions. The total volume of water it releases is akin to lumens, symbolizing the overall brightness a light source offers.

In technical terms, lumens, denoted by “lm,” is the SI unit (International System of Units) that measures luminous flux or the entirety of visible light produced by a source. To further illustrate, consider a light bulb emitting a certain brightness. If it’s partially obscured, the total visible light it emits changes, but its intensity in any unobscured direction remains constant. This total light output is what we refer to as lumens.

Simply put, the more lumens a light source has, the brighter it is. It’s the difference between a dribbling tap and a roaring waterfall. A soft bedside lamp might only give off around 400 lumens, while a powerful LED tube light in your kitchen could dazzle with 1500 lumens or even more.

So, the next time you’re browsing for light bulbs, remember: a higher lumen count means a brighter light ready to illuminate your space.

Lux (lx)

While lumens give us a sense of a light’s overall brightness, “lux” takes it a step further by considering the area over which that light is spread. Picture a spotlight shining on a stage. The intensity of that light, when concentrated on a specific spot, is measured in lux. Represented by “lx,” lux is the SI unit that describes the amount of light (lumens) falling on a square meter of a surface.

To simplify, imagine pouring a liter of water (lumens) over two different-sized areas: a small bowl and a large tray. The water’s depth (or concentration) will be greater in the bowl than in the tray. Similarly, the same amount of light will have a higher lux value when focused on a smaller area and a lower value when spread over a larger one.

Now, here’s where it gets interesting. If a lamp specifies its brightness in lux, it will often mention a distance. Why? Because the distance from the light source directly impacts the lux level. Let’s visualize this: Imagine you have a 200-lumen bulb in a LED floodlight. If this light shines on a surface that’s just one square meter, that surface receives the full 200 lx. But, if you move the floodlight back so it illuminates four square meters, the brightness dilutes. Now, each square meter gets only 50 lx.

In essence, lux gives us a clear picture of how intensely a surface is illuminated, factoring in both the light’s overall brightness and the area it covers.

Comparison: Candela Vs. Lumens Vs. Lux

Navigating lighting terms like candelas, lux, and lumens can be tricky. But, breaking them down:

  • Lumens: Think of it as the total brightness a light source offers. It’s like the overall glow of a light bulb.
  • Lux: This tells you how bright a specific spot will be when lit by the light source. Imagine how well-lit a book would be under a reading lamp.
  • Candela: It’s about the strength of light in one direction. A laser pointer, for instance, shines intensely in one direction but doesn’t light up an entire room.

In short, these terms help you pick the right light for the right purpose, ensuring you get just the brightness you need. Here’s a comparison table:

MeasurementDefinitionPractical Implication
LumensMeasures the total light output or how much light is emitted.Indicates the overall brightness a light source can provide when it’s not covered.
LuxIndicates the brightness of a surface at a specific distance from the light source.Tells you how illuminated a surface will be, especially useful for task lighting.
CandelaGauges the visible intensity of light in a particular direction from the source.Highlights the intensity of light in a specific direction, like a laser pointer’s beam.

Lumens vs. Candela: What’s the Difference?

Lumens: This term is all about the total light output. When a light fixture says it has 100 lumens, it means the light source can produce this amount of light in every direction. However, lumens don’t consider the design or how the light is directed. It’s like the raw power of a light bulb without considering how it’s used. So, while lumens give you an idea of a bulb’s potential brightness, they don’t paint the full picture of how the light will behave in a space.

Candela: Now, this is where direction comes into play. Candela measures the intensity of light in a specific direction. Think of it as the focused strength of the light. The term “steradian” might sound technical, but it’s just a way to describe the three-dimensional angle of the light. Imagine a spotlight shining on a stage; the area it illuminates is where candela comes into play.

For those who love a good comparison: 1 candela is equivalent to 12.57 lumens. But remember, it’s not always apples-to-apples. A laser light, for instance, might have a huge candela rating (because it’s so focused) but a low lumen value.

In essence, while lumens tell you about raw brightness, candela gives you an idea of how that brightness is directed. It’s the difference between a room filled with soft, even light and a focused beam highlighting a piece of art.

Lumens vs. Lux: What’s the Real Difference?

Lumens: Imagine you have two LED lamps, both boasting a 200 lumens rating. You’d think they’d shine with the same brightness, right? Not necessarily. Lumens tell you about the total light output, but they don’t factor in how that light is used or directed.

Lux: This is where the plot thickens. Lux measures how much of that light actually lands on a specific area. Think of it as the concentration of lumens on a given space. For a visual, imagine how a square meter area is lit up by a light source.

Here’s a simple equation to remember: 1 Lumen = 1 Lux over a square meter.

Now, consider two scenarios: a spotlight and a broad light. Both might have the same lumens, but the spotlight focuses its light, giving it a high lux value. In contrast, the broad light spreads its lumens over a larger area, resulting in a lower lux value. The design of the light fixture plays a crucial role in determining its lux.

In essence, while lumens tell you about the total light a source emits, lux gives you an idea of how that light is distributed over a space.

Foot-candles (fc)

A foot-candle is a unit of measurement for illuminance, which represents the amount of light that falls onto a surface. Specifically, one foot-candle is defined as the illuminance on a one-square-foot surface from a uniform source of light that is one foot away. In other words, it measures how bright the light appears to be on the surface it illuminates.

The term “foot-candle” is derived from the early English system of measurement, where it was considered the amount of light a single candle could produce on a one-square-foot surface located one foot away from the candle.

To relate it to more modern units: 1 foot-candle = 10.764 lux.

Foot-candles are commonly used in the United States, especially in the fields of photography, film, real estate, and interior design, to ensure adequate lighting levels for various tasks or settings.

How Can You Measure Light Using These Units?

Measuring the luminous intensity of light sources isn’t a task for the average consumer. It requires specialized equipment and is typically conducted in dedicated research laboratories. However, manufacturers understand the importance of these measurements and provide the relevant values on their product packaging or specifications. By familiarizing yourself with these units and their implications, you can make informed comparisons between different lighting products, ensuring you choose the right illumination for your project.

How to Choose Between Lights with Equal Lumens?

Choosing the right light bulb goes beyond just looking at brightness. While lumens indicate the brightness of a bulb, they don’t reveal its efficiency. To make an informed decision, especially when comparing bulbs with the same lumen output, it’s essential to understand the relationship between lumens and watts.

Lumens, Watts, and Efficiency – Breaking It Down

In any lighting store, the term “watts” is prominently displayed on most bulbs. Contrary to popular belief, watts don’t measure brightness. They represent the energy a bulb consumes. In simple terms, watts tell you about a bulb’s energy “appetite.”

On the other hand, lumens measure the total light output or brightness. Here’s the catch: two bulbs with the same wattage might not emit the same lumens. For example, a 1W LED bulb can shine brighter than a 1W halogen bulb because LEDs are more energy-efficient. They turn more of their consumed energy into light, while traditional bulbs like halogens lose much of it as heat.

To illustrate:

  • A 10W halogen might emit 140 lumens.
  • A 10W LED could dazzle with up to 1000 lumens.

So, while watts show a bulb’s energy consumption, lumens reveal its brightness. But how do you choose when faced with bulbs of the same brightness?

The Efficiency Factor: Lumens per Watt

Think of it this way: two dishes at a buffet might look and taste the same, but one could be less calorie-dense, making it a more efficient choice for those watching their diet.

Similarly, two bulbs might emit the same brightness, but one might be more energy-efficient. This efficiency is captured as lumens per watt. A bulb that gives more lumens for every watt it consumes is the more efficient choice.

In essence, when comparing bulbs with the same lumen output, look at their lumens per watt ratio. A higher ratio means you’re getting more brightness for less energy, benefiting both your wallet and the environment. To explore more, you could check this: Lumen To Watts: How To Choose The Right LED Lights?

Choosing the Right Light Measurement: What’s Best?

The ideal measurement for light depends on its purpose. For general room illumination, a bulb with a high lumen rating is ideal. But if you’re aiming to highlight architectural features or focus on specific areas, look for higher candela and lux values. When comparing bulbs of the same brightness, also consider the lumen/watt ratio to gauge energy efficiency. Reflect on your lighting needs, and with the insights from the guide above, you’ll be poised to make an informed choice.


Navigating the world of lighting might seem daunting, but with the right knowledge, it becomes a walk in the park. Remember, the perfect light for your space is not just about brightness but also about efficiency and purpose. If you’re still unsure about which LED to choose, don’t hesitate to consult an expert. At Sinolumi LED Ltd., we’re here to guide you to the ideal lighting solution tailored to your needs. Illuminate your spaces the right way. Contact us today for more information!”

While both lumens and lux measure light, they do so in different ways. Lumens represent the total amount of visible light emitted by a source. Lux, on the other hand, measures how much of that light actually lands on a specific area. In essence, lumens tell you about the total light a source emits, while lux gives you an idea of how that light is distributed over a space.

Candela measures the intensity of light in a specific direction. It’s like the focused strength of the light. While lumens tell you about the overall brightness a light source can provide, candela gives you an idea of how that brightness is directed in a particular path. For instance, a spotlight might have a high candela rating because of its focused beam, even if its overall lumen output is moderate.

To gauge the efficiency of a light bulb, you should consider the lumens per watt ratio. This ratio tells you how many lumens (brightness) a bulb produces for every watt of energy it consumes. A higher lumens per watt ratio indicates a more energy-efficient bulb. For example, an LED bulb that produces 1000 lumens while consuming only 10 watts has an efficiency of 100 lumens per watt.

While lumens measure the total light output, other factors can influence how we perceive brightness. The design of the bulb, the color temperature, and the directionality (how the light is spread) can all affect our perception. Additionally, the lux value, which considers the area over which the light is spread, can also play a role. Two bulbs with the same lumen rating might have different lux values depending on how they distribute their light.

Color temperature, measured in Kelvin (K), describes the color characteristics of light, ranging from warm (yellowish) to cool (bluish). A lower Kelvin number indicates a warmer light, while a higher number means a cooler light. For instance, a candle might have a color temperature of around 1,800K, while daylight is around 5,000K to 6,500K.

CRI, or Color Rendering Index, measures the ability of a light source to accurately reproduce colors compared to a natural light source. A CRI of 100 is considered perfect, meaning colors appear as they would under natural light. A high CRI value (close to 100) indicates that the light source will render colors more accurately. Both color temperature and CRI can influence how we perceive the brightness and quality of light, affecting the ambiance and mood of a space.

The beam angle is the degree of width that light emanates from a light source. Specifically, it defines how spread out the light is. A narrow beam angle, like that of a spotlight, focuses light onto a smaller area, creating a more intense and concentrated light. Conversely, a wide beam angle, like that of standard room lighting, spreads light across a broader area, resulting in a softer and more diffused illumination. When selecting lighting, it’s essential to consider the beam angle to ensure the light is distributed appropriately for the intended space or purpose.

While lumens measure the total light output, other factors can influence our perception of brightness in a room. These factors include the color temperature of the bulb (warm or cool light can be perceived differently), the directionality of the light (how it’s dispersed), the room’s color and reflectivity, and any obstructions or shades on the light fixture. Additionally, the human eye can perceive lights of different colors at varying brightness levels, even if their lumen outputs are the same. Therefore, it’s essential to consider the overall lighting environment and not just the lumen rating when evaluating brightness.

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