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Difference Between Gray Scale and Brightness of LED Display Screens

by | Mar 11, 2024 | Blogs | 0 comments

From giant outdoor LED advertising screens to indoor wall, LED displays are everywhere. When you’re shopping for LED displays, you’ve probably heard of the concepts of grayscale and brightness in LED displays, but how are they related and different?

What is LED display grayscale?

LED display grayscale

The Grayscale of an LED displays is the range of brightness levels between the darkest black and the brightest white that can be displayed. Essentially, it is the spectrum of gray levels that an LED pixel can produce. Each pixel in an LED display can be altered in intensity to produce different shades of gray, which enhances the depth and detail of the overall image. The number of gray levels an LED display can produce directly affects its ability to display detailed, lifelike images. Higher gray levels allow for finer transitions between tones, which improves image quality through more detailed textures and smoother gradations.

What is LED Display Brightness?

Difference Between Gray Scale and Brightness of LED Display Screens 1

The brightness of an LED screen is measured in nits or candelas per square meter (cd/m²) and refers to the intensity of light emitted by the screen. It measures the amount of light produced by the screen and affects how content is viewed in various lighting conditions. Brightness is a key attribute of LED displays, especially for outdoor LED displays in direct sunlight. Conversely, indoor screens may require lower brightness, but still need to be adjusted for ambient light conditions to ensure comfort and prevent eye strain.

The Difference Between Gray Scale and Brightness in LED Display Screens

Grayscale and brightness are intertwined in defining the visual quality of an LED display. Grayscale depth requires precise control of the brightness level of each pixel to render the various shades between black and white. They are a balancing link. Increasing the brightness of an LED screen without properly adjusting the grayscale can result in a faded image that loses exquisite detail. Conversely, a monitor with excellent grayscale but insufficient brightness may not achieve the desired effect, especially in bright environments.

Enhancing both attributes at the same time ensures that the display produces vivid, lifelike images with rich detail and contrast. Some top LED display manufacturers, such as DOITVISION often strive to optimize both for the intended use of the display, whether for indoor or outdoor environments where brightness is critical.

To clarify the difference between grayscale and brightness in LED displays, you can refer to the following:

AspectGrayscaleBrightness
DefinitionRefers to the range of shades between black and white that an LED can display, without involving color. It represents the variation in intensity of the light that pixels can produce to create different shades.The perceived intensity of the light emitted from the display, influencing how bright or dim the screen appears to the viewer.
Main PurposeUsed to transmit pictures, determining the clarity and detail of the image by allowing for the representation of different shades of gray.Controls the overall visibility of the display, affecting how easily the content can be seen under various lighting conditions.
Information ConveyedContains only brightness information to represent different shades from black to white, enabling the depiction of images in varying degrees of light without color.Represents the level of light intensity that the screen emits, impacting the display’s luminance and visibility.
Impact on Picture QualityAffects the detail and texture of the image, allowing for nuanced visual content with depth and realism through the representation of multiple shades.Influences the display’s ability to be seen and interacted with, especially in environments with varying light conditions, and affects the overall vibrancy of the image.
Relationship with ColorDoes not contain color information; focuses on brightness levels to achieve the perception of depth and detail in images.Works in conjunction with both color and grayscale to enhance the visual impact of the display, affecting how vivid and dynamic the content appears.

How to Adjust the Gray Scale of an LED Display

Adjusting the grayscale of an LED display screen involves calibrating the display to ensure that it accurately renders the full spectrum of grayscale tones between black and white. There are two main ways to control the grayscale of LEDs: adjusting the current and using pulse width modulation (PWM).

Adjusting the current flowing through the LED

The first method involves varying the amount of current flowing through the LED. Typically, LEDs have a continuous operating current of about 20 mA, except for red LEDs, which may exhibit saturation above a certain level. For most LEDs, the grayscale output is proportional to the current flowing through them, so adjusting the current can adjust the brightness level.

Pulse Width Modulation (PWM)

The second method is Pulse Width Modulation, which utilizes the visual ephemeral properties of the human eye. By rapidly turning LEDs on and off in very short periods of time (adjusting the duration (or width) of the “on” pulse relative to the “off” period (duty cycle)), PWM can simulate a variety of brightness levels. As long as the cycle of light pulses is repeated fast enough (ensuring a high refresh rate), the human eye perceives a steady light output without flickering, allowing control of gray levels. Given its suitability for digital control, PWM is widely used in LED displays, managed by microcontrollers or computers for dynamic content display.

LED Display Control Systems

Modern LED screens typically utilize PWM for grayscale control and integrate it into their control system, which consists of the main control box, the scanner board and the display panel itself. The control box receives pixel brightness data from the computer’s display card and redistributes it to multiple scanner boards. Each scanning board manages a specific number of rows (or columns) on the LED display, transmitting control signals to individual LEDs in serial mode.

Serial transmission of display control signals

There are two main methods for serial transmission of display control signals:

Centralized grayscale control: The scanning board breaks down the grayscale value of each pixel (via PWM) and sends pulse signals to activate the LEDs accordingly. This method requires fewer components, but transmits a large amount of data since multiple pulses are required for each pixel at different grayscale levels. Due to device frequency limitations, this method typically limits the display to lower gray levels, such as 16 color steps.

Distributed Pulse Width Modulation: In this method, the scanning board transmits an 8-bit binary grayscale value to each LED, and each LED has its own pulse width modulator to adjust its glow duration. This significantly reduces the need for high-frequency serial data transmission because fewer pulses are required per cycle, making it easier to achieve higher gray levels, such as 256 shades of color, while reducing data bandwidth.

In practice, to adjust the grayscale of an LED display, you may need specialized software and equipment. Below are the abbreviated steps:

Calibration equipment and software: Use a colorimeter or photometer designed for LED displays and calibration software, such as, Novastar LED Correction Software, which they can adjust to match standardized grayscale levels.

Setting the black level: First adjust the black level of the display to ensure that the darkest blacks are as deep as possible without losing detail in dark scenes.

Gamma Correction: This step involves adjusting the gamma value of the monitor. Proper gamma correction ensures that the grayscale is linear to the human eye, thus improving the overall image quality.

Final Test and Adjustment: After the initial adjustments, the monitor is tested with a series of images to ensure that the grayscale rendering is fully accurate.

What happens to an LED display if the grayscale is not set correctly?

Concert LED Display

If the grayscale settings on an LED display are configured incorrectly, it can lead to a variety of detrimental effects that can harm the performance of the display and the viewer’s experience. Examples of potential errors are listed below:

Loss of image detail and color distortion

Problem: Inadequate grayscale settings can reduce the number of brightness levels that can be displayed by the display, resulting in a loss of image detail.

Example effect: Subtle gradations of sky or texture in a natural scene become blurred and may not accurately reproduce colors, resulting in unnatural or skewed tones, especially noticeable in detailed or textured images such as human faces.

Reduced image contrast and sharpness

Problem: Incorrect grayscale affects the monitor’s ability to distinguish between the lightest and darkest elements, which affects overall contrast and image sharpness.

Example effect: Images may appear too bright or too dark, which impairs the depth and richness of visual content. Details may be blurred, making it difficult to distinguish between different elements in the image.

Wasted energy and shortened lifespan

Problem: Excessive grayscale settings may result in excessive brightness, increased energy consumption, and may shorten the life of the monitor.

Example effect: Higher operating costs and environmental impact due to wasted energy, while display quality deteriorates faster over time, including problems such as bad pixels or inconsistent brightness.

Decreased Audience Experience

Problem: The cumulative effect of these problems significantly reduces viewer enjoyment.

Example effect: A combination of blurry images, distorted colors, and insufficient contrast can lead to viewer fatigue, making prolonged viewing of a display uncomfortable or less engaging.

To summarize

Both the grayscale and the brightness of an LED display are important for achieving optimal image quality. Good brightness ensures that the LED display can be easily seen in a variety of lighting conditions, while depth of gray adds nuance and detail to the image, making the content lifelike, realistic and vibrant. Whether it’s outdoor advertising, indoor LED screens for entertainment, DOITVISION will do its best as possible, so feel free to contact us if you need a high quality LED display.

FAQS:

What is the difference between the grayscale of indoor and outdoor LED displays?

The differences between the grayscale requirements of indoor and outdoor LED displays, like this:

FeatureIndoor LED DisplaysOutdoor LED Displays
Grayscale RequirementsHigher grayscale levels (e.g., 10-bit, 12-bit)Lower grayscale levels compared to indoor, but still significant for maintaining color contrast and detail
Environmental LightingRelatively stable indoor lightingVaries significantly with direct sunlight and shadows
Proximity to AudienceCloser viewing distances require finer detail and color changesTypically viewed from greater distances; focus is on brightness and contrast
Image QualityRequires delicate and realistic image effects with richer colors and clearer detailsPrioritizes clear visibility under various lighting conditions, emphasizing brightness and contrast over detail
Grayscale PerformanceAimed at displaying more brightness levels for a nuanced visual experienceEnsures adequate grayscale to maintain color contrast and detail in strong light
Control System OptimizationEssential for enhancing grayscale and color reproductionCrucial for balancing brightness, contrast, and grayscale to optimize outdoor visibility

About the Author

Kris Liang

Kris Liang

Founder/LED display expert

Kiris Liang is the founder of Doitvision. 12 + years in LED visual industry. Full passion of LED, product designer & chief salesman. Looking for teammate of technical/ marketing / sales.

Connecting people relative with LED displays.

Email: kris@doitvision.net