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Brightness (Lumens)

Brightness, usually measured in lumens (lm), refers to the total amount of visible light emitted by a light source. The higher the lumen value, the brighter the light source, meaning it emits more light.Lumens is the international standard unit used to describe luminous flux, which is the amount of light emitted by a lamp or light source.

When selecting lighting, the lumen value is often used to determine the brightness requirement. For example, a 60W incandescent bulb emits approximately 800 lumens, while a LED bulb providing the same brightness may only use 10W of power.

Candela (cd) is the international unit of luminous intensity, used to measure the amount of visible light emitted by a source in a specific direction. Unlike lumens (lm), which represent the total luminous flux, candela measures light in terms of energy, time, and angle, emphasizing brightness in a particular direction. One candela is approximately equal to the luminous intensity of a standard candle in a given direction.

Candela holds significant importance in scientific research; however, its relevance is limited when evaluating how the human eye perceives light. In practice, candela is often applied to lighting applications that require high directional intensity, such as spotlights, automotive headlights, and signal lights.

Lux (lx) is the SI unit of illuminance, which measures how much luminous flux (lumens) falls on a given surface area. In other words, lux indicates the perceived brightness of light on a surface.One lumen evenly distributed over one square meter produces an illuminance of one lux.

Lux is widely used in lighting design and engineering to ensure proper brightness levels for different environments such as offices, roads, factories, sports arenas, and horticulture facilities.

Luminous efficacy is a measure of how efficiently a light source converts electrical power (watts) into visible light (lumens). It is expressed in lumens per watt (lm/W). A higher luminous efficacy means the light source produces more visible light with less energy

CRI (Color Rendering Index) is a quantitative measure of how accurately a light source reveals the true colors of objects compared to a natural reference light (such as sunlight or an ideal blackbody radiator).The index range is from 0 to 100. The higher the CRI, the better the color accuracy.

Color temperature is the degree of warmness or coolness of a light source, measured in kelvins (K). It indicates whether the light looks warm (yellowish), neutral, or cool (bluish). The higher the correlated color temperature (CCT), the “cooler” the visible light appears, with more blue tones. Conversely, the lower the CCT, the “warmer” the visible light appears, with more red tones. The typical color temperature range is 2700K to 6500K. CCT is critical in lighting design, as different color temperatures affect mood, productivity, and visual comfort. For example, warm light is preferred in homes and hotels, while cool light is better for offices, hospitals, and factories.

Diffuse reflection occurs when light strikes a rough or matte surface and is scattered uniformly in many directions, rather than being reflected in a single, mirror-like direction.It is a key principle in lighting design, as it helps reduce glare, soften shadows, and create a more uniform illumination.

SDCM is a measure used to quantify the variation in the color of light emitted by LED modules or light sources. It defines how much the color of an LED can deviate from its nominal color value and is often used in conjunction with MacAdam Ellipse to specify color tolerance.The range of SDCM is between 0 and 7, where 1 SDCM indicates no color deviation in LED strips, and 2-3 SDCM indicates virtually imperceptible color deviation.

Dielectric strength is the maximum electric field that a material can withstand without breaking down or becoming electrically conductive. It is typically measured in volts per unit thickness (V/mil or kV/mm) and is an important property in electrical insulation materials, including those used in LED drivers and modules. Dielectric strength represents the material’s ability to resist electrical breakdown under high voltage conditions.

Beam angle refers to the angular spread of light emitted from a light source, typically measured in degrees. It defines the distribution of luminous intensity and determines how concentrated or wide the light appears when projected onto a surface.

A narrow beam angle (e.g., 15°–30°) produces a focused light, ideal for accent lighting or spotlighting objects. A wide beam angle (e.g., 90°–120°) distributes light over a larger area, making it suitable for general illumination. Beam angle directly influences illuminance (lux) on the target surface, as a narrower beam delivers higher brightness within a smaller area.

Lumen Depreciation refers to the gradual reduction in light output (lumens) of an LED light source as it ages. Over time, the LED’s luminous flux decreases due to various factors, including the degradation of the LED chip, thermal stress, and the wear of other components.

LM-80 is a standardized testing procedure established by the Illuminating Engineering Society (IES) to evaluate the lumen depreciation of LED light sources over time. It specifies how to measure the light output of an LED module, LED chip, or array at set intervals under controlled conditions. LM-80 results are often used to calculate L70 ratings, which indicate the number of hours it takes for the LED’s light output to degrade to 70% of its original value.

Thermal resistance is a measure of a material’s ability to resist the flow of heat. It is a key factor in the thermal management of LED modules and other electronic devices. Thermal resistance determines how efficiently heat is dissipated from the LED chip to the surrounding environment or heat sink. Thermal resistance is typically expressed in °C/W (degrees Celsius per watt), which represents the temperature rise (in °C) per watt of power dissipated. LEDs with high thermal resistance may overheat, causing lumen depreciation and reduced performance. 

LED junction temperature refers to the temperature at the junction (interface) between the LED chip and its package. It is a critical factor in determining the performance and longevity of an LED light source. The junction temperature rises as the LED operates, especially under high currents or poor thermal management. Junction temperature is often higher than the ambient temperature due to the heat generated within the LED chip during operation. If the junction temperature exceeds the recommended limits, it can lead to lumen depreciation, reduced light output, and ultimately, failure of the LED.

Oxidation refers to the chemical reaction between a material,, and oxygen in the environment, resulting in the formation of an oxide layer. This reaction can significantly alter the material’s surface properties, including conductivity, strength, and corrosion resistance.In electronic components like LED modules, oxidation can occur on metal parts such as solder joints, pins, or contacts, causing degradation in electrical conductivity and mechanical stability.

IP Rating (Ingress Protection Rating) defines the level of protection provided by an enclosure against the intrusion of solid objects (dust, debris) and liquids (water). It is expressed as “IP” followed by two digits: IPXX.

The first digit (0–6) indicates the degree of protection against solid objects:0: No protection、6: Dust-tight, complete protection against dust ingress. The second digit (0–9) indicates the degree of protection against water ingress: 0: No protection、8: Protection against continuous immersion beyond 1 meter.

Reverse voltage protection is a circuit design feature that prevents damage to electronic components, including LEDs and LED drivers, when voltage is applied in the wrong polarity. It ensures that current flows only in the intended direction. Reverse voltage occurs when the positive and negative terminals of a power supply are connected incorrectly.

LED lighting can operate on either DC (Direct Current) or AC (Alternating Current) power. DC power provides a constant voltage or current in one direction, ensuring stable operation of LED modules, reducing flicker, and improving energy efficiency. It is commonly used in battery-powered devices, DC adapters, and solar-powered systems. AC power delivers voltage and current that periodically reverse direction and is the standard mains electricity in residential, commercial, and industrial environments. LEDs typically require an LED driver to convert AC to DC for proper operation, making AC suitable for commercial lighting, street lighting, industrial fixtures, and residential lighting.

LED drivers are generally classified as Constant Current (CC) and Constant Voltage (CV) types. Constant current drivers maintain a stable output current, ideal for LED modules that require a fixed current, ensuring consistent brightness and preventing overcurrent damage. Constant voltage drivers maintain a stable output voltage, suitable for multiple LEDs connected in parallel or strip lighting systems, allowing flexible installation and expansion. Choosing the appropriate driver type according to the LED application ensures the reliability, lifespan, and performance of the lighting system.

Power factor (PF) is the ratio of real power (the power actually used by a device) to apparent power (the total power supplied by the source). It indicates how effectively electrical power is being converted into useful work.

Inrush current is the maximum instantaneous current drawn by an electrical device when it is first powered on. In LED drivers and other electronic equipment, this current can be significantly higher than the device’s normal operating current.

Pulse Width Modulation (PWM) is a technique used to control the brightness of LEDs by switching the current on and off at a high frequency. By adjusting the duty cycle—the proportion of time the LED is on versus off—PWM effectively controls the perceived brightness without changing the LED’s color or efficiency.