![]() ![]() Both of these flashlights can claim that they output 18,000 candelas even though they are clearly not performing at the same level.įlashlight A illuminates half of our subject, as does Flashlight B. Since candela is the measure of light intensity-not total light output. This gives us a general idea of the capabilities of the flashlight but leaves much to be questioned about the performance. ![]() Long Story Short: Lumens is a measure of total light output, while candela is a measure of light intensity.Ī LED flashlight, for example, with the variable zoom and variable LED output, can change zoom (increase or decrease the light intensity - candela) or can change the LED total light output (increase or decrease the total amount of light - lumens).Candela is a term that refers to the amount of visible light at any one point, within a specific light pattern.Ĭandela values measure the intensity of light at a specific location, and this number, just as lumen values, can be used to mislead.įor instance, you could have two different flashlights (Flashlights A and B) that both claim to be 18,000 candelas. ![]() So, if You have a 1000 lumens LED flashlight, depending on the exact LED light source, You can expect a power requirement of 10-15 Watts from the flashlight's battery pack. Also, they depend on the LED light color, if the light is dimmed and similar. Note: These values change over time with technological advancements, especially for LED light sources. ![]() The following comparison chart lists typical luminous flux (lumens) for various light sources and their electric power consumption (given in Watts): Lumens So, depending on the beam angle, the very same 1500 lm provides the light intensity of ~119 and ~15789 candelas. If the light is focused in a 20° beam (0.095 sr), the light intensity is: If we assume that a 14W LED bulb provides 1500 lumens, then if the light is radiated in all directions, the intensity is: Φ v = 1 cd * 12.56 sr = 12.56 lm 14W LED Bulbġ4W LED bulbs are very often used in homes to replace old 100W incandescent bulbs and 25W fluorescent lights.Īs such, they are able to provide a light output of ~1400-1700 lumens, depending on the model, light temperature, and similar. If that light is radiated in all directions uniformly, the light (luminous) flux is: Since a sphere has a solid angle of 4π sr (~12.56 sr), a light source that radiates 1 (one) candela of light in all directions features a total luminous flux of:ġ cd x 4π sr = ~12.56 cd sr = ~12.56 lm Few Examples CandleĪn ordinary candle emits light with the luminous intensity of roughly 1 cd - hence the name "candela." The lumen (lm) is related to the candela (cd) and steradians (sr) as: "Particular direction" is a solid angle (also known as a spatial angle) given in steradians (sr) and labeled as Ω.įor example, a sphere features a solid angle of 4π sr (~12.56 sr), while a cone with a 60° angle features a solid angle of one steradian (1 sr). Simplified, candela (cd) measures the amount of light in a particular direction given by a light source, while lumens (lm) measure the total amount of light given by a light source. Lumens: What Is The Difference?Ĭandelas and lumens are used to describe the performances of various light sources, making it very useful to know what they actually mean.īoth candelas and lumens are units of the International System of Units, and both refer to (simplified) the amount of light. ![]()
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