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Among the core parameters of LED displays, brightness is a critical indicator that determines display performance, scene adaptability and device lifespan, directly affecting picture clarity and user visual experience. Unlike intuitive parameters such as resolution and refresh rate, the selection and interpretation of brightness require consideration of physical principles, usage scenarios and technical characteristics. Many users fall into the misconception that "higher brightness is better" when purchasing or using LED displays. Starting from the core definition of brightness, this article thoroughly breaks down the calculation logic of brightness, the differences in brightness between indoor and outdoor products, and the multi-dimensional impact of brightness on LED displays. It aims to help industry practitioners and ordinary users develop a scientific and rational understanding of brightness.

I. Core Definition of LED Display Brightness

LED display brightness refers to the luminous flux density emitted per unit area of the screen at a normal viewing angle. The industry standard unit is candela per square meter (cd/m², also known as nit), which physically represents the luminous intensity of the display surface in the standard viewing direction. The core value of brightness lies in balancing ambient light and displayed content—screen brightness must match the intensity of ambient light to deliver a clear and comfortable visual experience, rather than simply pursuing a higher numerical value. Key related definitions are as follows:

1. Luminance (L): The brightness of an LED display refers to the maximum luminous intensity per unit area of the screen in the normal direction. For full-color displays, it specifically denotes the brightness of a full white screen when R, G, and B channels are all at maximum grayscale.
2. Unit: 1 nit = 1 cd/m² (candela per square meter).
3. Nominal Brightness (Maximum Brightness): The peak brightness measured under standard conditions (25°C, full white screen, standard voltage), as marked in the product specification sheet.
4. Average Brightness: The average brightness of a uniformly illuminated full screen, which is more focused on in engineering applications.
5. Brightness Uniformity: The consistency of brightness across different areas of the screen, expressed as a percentage of "maximum deviation/average brightness"—a smaller value indicates better performance (industry standard: ≤5%).

II. Calculation of LED Display Brightness (Detailed Outdoor Display Example)

The brightness of an LED display follows the derivation logic: single LED brightness → single pixel brightness → theoretical full-screen brightness → actual brightness correction. Outdoor displays require high brightness and use specialized lamp bead specifications, making their calculation logic more aligned with real-world engineering scenarios. Below is a detailed breakdown of the complete calculation process using a mainstream outdoor P5 full-color display as an example.

(I) Core Basic Parameters (Outdoor P5 Full-Color Display)

Before calculation, four categories of outdoor display-specific core parameters (all standard specifications provided by manufacturers) must be clarified:

1.  Single LED Lamp Bead Brightness: Outdoor full-color displays have much brighter lamp beads than indoor ones, with typical specifications: red 1100 mcd, green 1400 mcd, blue 180 mcd (unit: millicandela, mcd; 1 cd = 1000 mcd).
2. Pixel Configuration: Mainstream outdoor displays use a 1R1G1B configuration (1 red, 1 green, 1 blue), with the brightness ratio of red, green and blue meeting white balance requirements.
3. Pixel Density: A P5 outdoor display has a pixel pitch of 5 mm, with a pixel density of 40,000 DOT/m² per square meter.
4. Scan Mode: Outdoor displays commonly use static scanning (1/1S) or low scan ratios (e.g., 1/4S). This example uses 1/8 scanning (low scan ratios for outdoor displays enhance brightness and stability).
5. Light Attenuation Rate: Affected by packaging technology, dust-proof masks, environmental dust and sunlight aging, the light attenuation rate of outdoor displays is approximately 18%-22% (20% is used for calculation in this example).

(II) Step-by-Step Calculation Formula and Practical Calculation

1. White Balance Brightness Calculation Formula

White Balance Ratio: Red brightness : Green brightness : Blue brightness = 3:6:1

White Balance Brightness Formula (calculated proportionally using the minimum brightness value):

Single pixel brightness (cd) = (Blue LED brightness × 10) ÷ 1000

Practical Calculation:

Single pixel brightness = (180 × 10) mcd ÷ 1000 = 1800 mcd ÷ 1000 = 1.8 cd

2. Theoretical Full-Screen Brightness Calculation

Theoretical brightness refers to the maximum brightness under ideal conditions (no light attenuation, lamp beads operating at full load).

Formula:

Theoretical full-screen brightness (cd/m²) = Single pixel brightness (cd) × Pixel density (DOT/m²) ÷ Scan ratio

Practical Calculation:

Theoretical brightness = 1.8 cd × 40,000 DOT/m² ÷ 8 = 9,000 cd/m²

3. Actual Brightness Correction (Deducting Light Attenuation)

Actual brightness refers to the effective luminous brightness of the screen in a real environment, with deductions for light loss caused by packaging, masks, dust, etc.

Formula:

Actual brightness (cd/m²) = Theoretical brightness × (1 - Light attenuation rate)

Practical Calculation:

Actual brightness = 9,000 cd/m² × (1 - 20%) = 7,200 cd/m²

4. Reverse Derivation (Lamp Bead Brightness Selection Verification)

Given the target brightness of an outdoor display, the required brightness of a single lamp bead can be reversely derived for model verification:

Formula:

Single lamp bead brightness (mcd) = Target brightness (cd/m²) ÷ (1 - Light attenuation rate) × Scan ratio ÷ Pixel density (DOT/m²) × 1000 (1 cd = 1000 mcd) ÷ 10 (white balance ratio 3:6:1, using blue as the unit value)

Example: If the actual brightness of a P5 outdoor display is required to be ≥7,200 cd/m², the single lamp bead brightness is reversely derived as:

Single lamp bead brightness = 7200 ÷ 0.8 × 8 ÷ 40000 × 1000 ÷ 10 = 180 mcd

The overall brightness of an LED display is not a simple superposition of single LED lamp bead brightness. Instead, it requires comprehensive calculation based on lamp bead specifications, pixel configuration, scan mode, screen area and other parameters, which is divided into two core stages: theoretical brightness calculation and actual brightness correction. Below is a detailed explanation of the calculation logic using industry-standard formulas and practical examples.