What is Candela and Lumens?
Candela (cd)
- Definition: Candela is the SI unit of luminous intensity. It measures the amount of light emitted by a source in a particular direction.
- Meaning: Think of candela as the “brightness” of a light source when viewed from a specific direction. For example, a laser beam, which focuses light in one direction, has a high candela value.
- Practical Example: A common candle emits light with an intensity of roughly 1 candela. This is where the unit gets its name.
Lumens (lm)
- Definition: Lumens measure the total amount of visible light emitted by a source in all directions. It is the SI unit for luminous flux.
- Meaning: Lumens describe how much light a source produces overall, regardless of the direction. A higher lumen value means a brighter light overall.
- Practical Example: A standard 60-watt incandescent bulb produces around 800 lumens.
Candela to Lumens Conversion
Formula: Candela to Lumens
The luminous flux (\( \Phi_v \)) in lumens is calculated as:
\[ \Phi_v (\text{Lumens}) = I_v (\text{Candela}) \times \Omega (\text{Steradians}) \]
Where:
- \( \Phi_v \) = Luminous flux in lumens
- \( I_v \) = Luminous intensity in candela
- \( \Omega \) = Solid angle in steradians
Formula: Solid Angle (\( \Omega \))
The solid angle is calculated as:
\[ \Omega (\text{Steradians}) = 2 \pi \times (1 - \cos(\frac{\theta}{2})) \]
Where:
- \( \theta \) = Cone apex angle in degrees
Combined Formula
Combining the two formulas:
\[ \Phi_v (\text{Lumens}) = I_v (\text{Candela}) \times [2 \pi \times (1 - \cos(\frac{\theta}{2}))] \]
Example Calculation
If the luminous intensity is 10 candela and the cone apex angle is 60 degrees:
\[ \Omega = 2 \pi \times (1 - \cos(60^\circ / 2)) = 2 \pi \times (1 - \cos(30^\circ)) \]
\[ \Phi_v = 10 \times \Omega = 10 \times [2 \pi \times (1 - \cos(30^\circ))] \]
Difference Between Candela and Lumens
| Aspect | Candela | Lumens |
|---|---|---|
| What it Measures | Luminous intensity (brightness in a specific direction) | Total light output (overall brightness) |
| Direction | Directional (focused light) | Omnidirectional (all light emitted) |
| Example | A flashlight with a narrow beam | A light bulb lighting a whole room |
Relationship Between Candela and Lumens
The connection depends on the geometry of the light source. Specifically:
Lumens=Candela×Solid Angle (steradians)
A light source with a high candela value but a narrow beam might produce fewer lumens than a source with a lower candela value but a wider beam.
Analogy
- Candela: How bright the light seems from a specific angle (like the beam of a flashlight).
- Lumens: How much light the source spreads out in total (like the brightness of a light bulb in a room).
Candela to Lumen conversion Table
| Question | Answer |
|---|
| 100,000 candela to lumens | 628,318.53 lumens |
| 66,000 candela to lumens | 414,498.88 lumens |
| 1 million candela to lumens | 6,283,185.31 lumens |
| 1000 candela to lumens | 6,283.19 lumens |
| 1600 candela to lumens | 10,053.07 lumens |
| 3000 candela to lumens | 18,876.62 lumens |
| 544,000 candela to lumens | 3,418,706.94 lumens |
| 42.3 billion candela to lumens | 265,330,313,655.88 lumens |
| Candela to lumens conversion | Dependent on values of candela and angle |
| 300 candela to lumens | 1,884.99 lumens |
| 7 million candela to lumens | 43,964,203.06 lumens |
| 10,000 candela to lumens | 62,831.85 lumens |
| 230 candela to lumens | 1,444.80 lumens |
| 18,000 candela to lumens | 113,588.07 lumens |
| Candela to lumens formula | Φv = Iv × (2Ï€(1 – cos(θ/2))) |
How to use Candela to Lumen calculator
How to Use the Candela to Lumen Calculator:
– Step 1: Enter the luminous intensity in candela (cd).
– Step 2: Enter the cone apex angle in degrees (°).
– Step 3: The calculator computes the solid angle using:
Ω = 2Ï€ × (1 – cos(θ / 2))
– Step 4: It calculates the luminous flux (lumens) using:
Φv = Iv × Ω
– Step 5: View the result, showing the luminous flux in lumens (lm).
Example:
– Enter 10 cd for luminous intensity.
– Enter 60° for the apex angle.
– The result will show luminous flux as 7.54 lumens.