Side-Emitting SMD LED Brightness and Lumen Value
Professional Guide to LED Optical Performance & Core Parameters
The brightness of side-emitting SMD LEDs is highly related to the LED beam angle. Smaller angles deliver higher brightness. Different manufacturing processes also affect service life. Color temperature is irrelevant to brightness, but brightness is directly linked to lumen value.
Side-Emitting LED Brightness & Beam Angle Relationship
LED beam angle is a critical factor affecting brightness perception. Narrower beam angles concentrate light, resulting in higher luminous intensity, while wider angles disperse light and reduce intensity.
| LED Type |
Beam Angle |
Luminous Intensity |
| 5mm White LED |
180° |
Only hundreds of mcd |
| 5mm White LED |
15° |
10,000 – 20,000 mcd |
| High-Power LED (Outdoor) |
– |
Extremely high brightness |
High-power LEDs for outdoor use include 1W, 3W, 5W single chips. Multi-chip high-power modules can reach hundreds of watts for large-scale lighting projects.
Core Optical Concepts of Side-Emitting SMD LEDs
1. Brightness (Luminance)
Brightness describes the light intensity perceived by human eyes from a specific direction. Unit: candela per square meter (cd/m²), symbol: L.
It represents luminous flux per unit area and unit solid angle, equal to 1 candela of luminous intensity emitted from a 1-square-meter surface.
2. Luminous Intensity of Side-Emitting SMD LED
Luminous flux refers to the total light energy emitted by a light source into space. Light distribution varies among different light sources.
Unit: candela (cd). Definition: luminous flux emitted within one steradian (solid angle unit).
Formula: 1 cd = 1 lm / 1 sr
3. Luminous Flux (Lumen Value)
Human eyes have different sensitivity to different wavelengths, so radiant power cannot directly measure light energy. We use luminous flux — based on human visual perception — as the standard unit.
Symbol: Φ
Unit: lumen (lm)
4. Color Rendering Index (CRI / Ra)
Ideal artificial light should match natural light for accurate color recognition. Color rendering defines how well a light source reveals the true colors of objects.
Abbreviation: Ra
Testing standard: DIN6169 uses 8 standard color samples. Smaller color difference between test and standard light source = better color rendering.
Side-Emitting LED LED Brightness Lumen Value LED Beam Angle Luminous Intensity Color Rendering Index SMD LED
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