Don't let your annoyance over not knowing the distinction between candela, lux, and lumens while you're standing in a hardware store comparing light bulbs and cursing your school for not teaching you Latin get the better of you. The terminology used for light output measurements can vary depending on each package's specifications. It may be as frustrating to not understand the distinction between the words used to measure lighting as it is to not understand the difference between the metric and imperial systems.
So that you can grasp the specifications the next time you purchase lightbulbs or fixtures without needing to be proficient in a dead language, we shall define candela, lux, and lumens.
Candela
Candela, which in Latin means "candle," refers to candlepower. Luminous intensity, commonly known as candela, or cd, quantifies how much light the fixture produces in a certain direction.
Candela is suitably called since it was created when candles were the most popular kind of illumination. The quantity of light a candle emits in one direction is about equal to one candela. Because candela only measures in one direction, if you partially cover a light source that only measures one cd in your room with your hand, the remaining portion of the light will still measure one cd. For measuring fixtures with a focussed beam of light, the candela unit works well.
For instance, because the objective is to focus the light beam in one direction, it would be preferable to measure a spotlight that is pointed at your home in the yard using candela units. In such case, a high candela number would be more significant than a high lumen value.
Lumen
The luminous flux, often known as the lumen or lm, is a unit of measurement for the total quantity of visible light that a lighting fixture produces in all directions. The most common unit of measurement for illumination is lumens.
12.57 lumens are equal to one candela. The lumen number would drop to 6.28 lm if you covered half of the identical one-cd bulb in your room since it measures the total quantity of light, which has been reduced in half as a result of the obstructed lighting.
Imagine that you are in charge of lighting a large area, such as a garage or a meeting room. In either scenario, the lumen value rather than the candela value of the fixture would be more important. For optimal lighting of the whole room, a high lumen number will ensure that the light is shining in all directions.
Lux
Lux, which in Latin means "light," is a unit of measurement for the amount of light that must illuminate a certain surface per unit area. In other terms, it counts the amount of light.
A single lumen per square meter is equal to one lux, denoted by the symbol lx. The lux value of the source you choose for task lighting should be higher. The most used method for measuring lamps is lux.
To Put It Plainly...
Candela
Candela measures the amount of light that the fixture produces in a certain direction.
Torches, spotlights, laser pointers, and other lighting sources that need illumination in a single direction across long distances require higher candela levels.
Lumen
The total quantity of visible light that a lighting fixture produces in all directions is measured in lumens.
Higher lumen ratings are crucial for light bulbs that must provide a lot of lighting across a large area.
Lux
The amount of light needed to illuminate a surface is measured in lux.
To estimate how much light will illuminate your surface area, lights need to have lux values.
