Online Candela to lumens Calculator
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Candela to lumens calculator
Candela (cd) to lumens (lm) calculator and how to calculate.
Candela to lumens calculator
Enter the luminous flux in lumens, apex angle in degrees and press the Calculate button
to get the luminous intensity in candela:
Candela to lumens
Lumens are now the most common measurement for a light bulb. The lumen (lm) is a measurement of luminous flux, or the total amount of visible light. To put it simply, the lumen rating is how much total visible light is produced by a light source. To show the difference between lumens and candela, let’s go back to the example previously used for candela with the partially obscured light bulb. For a bulb emitting 1 cd, that bulb would also have a luminous intensity of 12.57 lm. Obscuring half the bulb (making it a hemisphere instead of a full sphere), a 1 cd bulb will emit only 6.28 lm. This is because lumens measure the total amount of visible light from a light source.
So why all of the different ratings? Since candelas, lux, and lumens are all measuring something different, you can gain insight into how a lamp is useful. A laser pointer will have an extremely low lumen value but a very high candela rating, since a laser pointer doesn’t give off very much light but is visible from great distances. Light bulbs are usually listed in lumens to show how much illumination the uncovered bulb produces. And lamps will often display a lux value for a set distance to give you an idea of how bright your surface will be for task lighting.
For uniform, isotropic light source, the luminous flux Φv in lumens (lm) is equal to the luminous intensity Iv in candela (cd),
times the solid angle Ω in steradians (sr):
Φv(lm) = Iv(cd) × Ω(sr)
The solid angle Ω in steradians (sr) is equal to 2 times pi times 1 minus cosine of half the cone apex angle θ in degrees (°):
Ω(sr) = 2π(1 - cos(θ/2))
The luminous flux Φv in lumens (lm) is equal to the luminous intensity Iv in candela (cd),
times 2 times pi times 1 minus cosine of half the apex angle θ in degrees (°):
Φv(lm) = Iv(cd) × ( 2π(1 - cos(θ/2)) )
So
lumens = candela × ( 2π(1 - cos(degrees/2)) )
Or
lm = cd × ( 2π(1 - cos(°/2)) )
Lumens and candela are both lighting measurement units, but they measure different aspects of a lighting device. Knowing about the difference between lumens and candelas will help you choose lighting devices that are ideal for your workplace. More importantly, this knowledge will ensure that your lighting supplier does not cheat you. Some may try to convince you about the merits of a lighting device by quoting impressive lumens or candela numbers. However, they may not be relevant for your needs.
Defining Lumens and Candela
Lumens refers to the total amount of light a lighting apparatus emits. We represent lumens as L. The higher the lumens value of a lighting device, the greater the area it illuminates. On the other hand, candela refers to the amount of light emitted by a lighting device in a particular direction. We represent candela with CD.
The lumens unit does not consider the spread or divergence of the light being emitted by the device. But the candela value of a lighting device is concerned primarily with a focused beam of light. For instance, a standard fluorescent lighting device that emits a wide-spread beam can have a rating of 1,700 lumens and 135 candelas. But if the light emitted from this apparatus narrows and must shine within a 20-degree beam, then its candela value will increase to 18,000.
Candela is another word for candlepower. Candlepower measurement is from times when the candle was the primary source of illumination. The word candlepower was substituted with the term candela in 1948. One candela is approximately equal to the light that a candle with specific dimensions, produces. In this context it is worth mentioning that the term Maximum Beam Candlepower (MBCP) is often used to refer to the maximum intensity of the focused beam of light emitted usually from the center of the lighting device, which is usually the source, and projected in a single direction.
So what is the difference?
The difference between lumens and candela can be better understood in the context of a comparison between a pencil torch and an incandescent or a fluorescent bulb. The torch has a high candela value because its light concentrates into a single point. It projects in a single direction as a high-intensity beam. While buying a torch, don't concern yourself with its lumens value because you will only use this device to illuminate a very small area. On the other hand, an incandescent light or a fluorescent light bulb has a low candela value but a high lumens value. This is because it emits a greater amount of light spread over a larger area than the pencil torch.