LED Lighting Technical Terms Explained
Lumens, Lux, Candela, Watt, CRI, Color Temperature, Beam Angle, IP Rating — everything you need to know to read any LED spec sheet with confidence.
When comparing LED products from different suppliers, the spec sheets are full of technical jargon — lumens, lux, candela, CRI, Kelvin, IP rating. Understanding these 10 core terms is the key to choosing the right LED light for your project and avoiding costly mistakes.
1. Luminous Flux — Total Light Output
Luminous Flux / 光通量
What it measures: The total amount of visible light energy a light source emits in all directions. This tells you how much light a lamp produces overall.
Unit: Lumen (lm)
Symbol: Φ
In simple terms: Higher lumens = brighter total light output. A 100W incandescent bulb produces about 1,600 lm, while a 20W LED can produce the same.
2. Luminous Intensity — Focused Light Strength
Luminous Intensity / 发光强度
What it measures: The concentration of light emitted in a specific direction. Two lamps with the same lumens can have very different intensity if one focuses the beam.
Unit: Candela (cd)
Symbol: I
In simple terms: A flashlight has high candela because all the light is focused forward, even if total lumens are modest.
3. Illuminance — Light on a Surface
Illuminance / 照度
What it measures: The amount of light that actually reaches and covers a surface — a desk, a wall, the floor, or a work area.
Unit: Lux (lx)
Symbol: E
In simple terms: Lux tells you how bright a surface looks. An office desk typically needs 300–500 lux for comfortable reading.
4. Luminance — Perceived Brightness
Luminance / 亮度
What it measures: The brightness your eyes perceive when looking at a surface or light source. It depends on how much light the surface reflects toward your eyes.
Unit: cd/m² (candela per square meter)
In simple terms: This is the brightness you actually see — a phone screen at 500 cd/m², or a road sign at night.
5. Power Consumption — Electricity Used
Power / 功率
What it measures: How much electricity the lamp consumes.
Unit: Watt (W)
Symbol: P
Important: Watt is NOT a measure of brightness. A 10W LED can be brighter than a 60W incandescent bulb. Always check lumens, not watts, when comparing brightness.
| LED Wattage | Lumens | Equivalent Incandescent |
|---|---|---|
| 5W | ~400 lm | 40W bulb |
| 10W | ~800 lm | 60W bulb |
| 20W | ~1,600 lm | 100W bulb |
| 50W | ~5,000 lm | 300W bulb |
6. Luminous Efficacy — Energy Efficiency
Luminous Efficacy / 光效
What it measures: How much light you get for every watt of electricity consumed. This is the key metric for energy efficiency.
Unit: lm/W (lumens per watt)
In simple terms: Higher lm/W means more light with less electricity. Modern quality LEDs achieve 130–180 lm/W, while incandescent bulbs only reach 10–15 lm/W.
7. Color Temperature — Light Color
Color Temperature / 色温
What it measures: The color appearance of the light, from warm yellow to cool blue-white. Measured in Kelvin (K).
2700K – 3000K
Warm White
Homes, hotels, restaurants
4000K
Natural White
Offices, retail, schools
5000K – 6500K
Cool White
Warehouses, factories, outdoor
8. CRI — Color Rendering Index
CRI / 显色指数
What it measures: How accurately the light reveals the true colors of objects, compared to natural sunlight.
Range: 0–100. Higher CRI = more accurate color reproduction.
| CRI Range | Quality | Best Applications |
|---|---|---|
| ≥ 80 | Good | Offices, corridors, general commercial |
| ≥ 90 | Excellent | Retail stores, hotels, museums, galleries |
| ≥ 95 | Superior | Photography studios, color-critical work |
9. Beam Angle — Light Spread
Beam Angle / 光束角
What it measures: The angle at which light is emitted from the lamp, determining how widely or narrowly the light spreads.
| Beam Angle | Type | Best For |
|---|---|---|
| 10° – 24° | Spot / Narrow | Track lighting, accent lighting, artwork |
| 36° – 60° | Medium | Downlights, retail displays |
| 90° – 120° | Flood / Wide | Panel lights, office lighting, general area |
10. IP Rating — Dust & Water Protection
IP Rating / 防护等级
What it measures: The level of protection against dust and water. Format is IPXX — first digit = dust protection, second digit = water protection.
| IP Rating | Protection Level | Typical Applications |
|---|---|---|
| IP20 | No special protection | Indoor — living rooms, offices |
| IP44 | Splash-proof | Bathrooms, covered outdoor areas |
| IP65 | Dust-tight + rain-proof | Outdoor flood lights, street lights |
| IP66 | High-pressure water resistant | Industrial, harsh environments |
| IP67 / IP68 | Waterproof (submersible) | Underwater, tunnel, extreme outdoor |
How All Terms Connect
The Lighting Chain
Here is how these concepts flow from power to what you actually see:
Watt (W) — The lamp consumes electricity
→
Lumen (lm) — The lamp converts it into total light
→
Candela (cd) — Light travels in a focused direction
→
Lux (lx) — Light reaches a surface
→
Luminance (cd/m²) — Your eyes perceive the brightness
Quick Reference
Need Help Choosing the Right LED Lights?
At ANGLIGHTING, every product listing includes clear specifications for lumens, wattage, CRI, color temperature, and IP rating. Our team can help you select the perfect lighting solution for your project.
