LED Display Contrast Ratio

Sep 23, 2022 | knowledgebase | 1 comment

LED Display Contrast Ratio Definition

According to the definition of industry-standard SJ/T11281-2007 “Light Emitting Diode (LED) Display Test Method,”Contrast is a term that describes how bright or dark the image on an advertising LED screen is. It is calculated by comparing the brightness of the white and black colors on the screen. The contrast ratio is a number that shows how much brighter the white is than the black.

For example, an LED display contrast ratio of 1000:1 means that the white is 1000 times brighter than the black. The higher the contrast ratio, the more clear and colorful the image is. The lower the contrast ratio, the more dull and blurry the image is.

Table of Contents

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LED Display Contrast Ratio Definition
Static and dynamic contrast ratio
Different Contrast ratios Among COB, GOB, SMD led displays

SMD LED Display: Black SMD LEDs VS White LED Screen.
Contrast Ratio: GOB LED Display VS SMD LED Display
LED Display Contrast Ratio: COB VS GOB
LED Display contrast ratio Flip chip COB vs Lateral Chip COB

High Contrast COB LED Display
High Contrast Outdoor LED Display
Black LED Rental Display

Static and dynamic contrast ratio

: The contrast ratio can be measured in different ways, such as static contrast ratio and application contrast ratio. The static contrast ratio is measured in a completely dark room environment, and it is usually very high, as high as millions to one. The application contrast ratio is measured at an ambient illumination of 10±10% lx, and it is more realistic and practical. According to industry standards, an LED display application contrast ratio greater than or equal to 5000:1 is the highest level of C.

Different Contrast ratios Among COB, GOB, SMD led displays

SMD LED Display: Black SMD LEDs VS White LED Screen.

Black SMD LED in small sizes, make them perfect for incorporation into instruments and devices. The smaller the chip size, the higher the contrast ratio of the LED display. This is because a smaller chip leaves more black space on the display, which reduces the brightness when the LED is off. Even though a smaller chip also reduces the brightness when the LED is on, the contrast ratio still increases significantly.

Black LEDs have a higher contrast ratio than white LEDs, which means they can produce darker blacks and more uniform colors. The contrast ratio of black LEDs is 8000:1, while the contrast ratio of white LEDs is 3000:1.

Power consumption: Black LEDs consume less power than white LEDs, which makes them more energy-efficient and eco-friendly. The power consumption of black LEDs is 350/m2, while the power consumption of white LEDs is 410/m2.
Brightness: White LEDs have a higher brightness than black LEDs, which means they can be more visible in bright environments. The brightness of white LEDs is Max. @2000cd/m2, while the brightness of black LEDs is Max. @1500cd/m2.
Display effect: Black LEDs can display black or gray colors more accurately and smoothly than white LEDs, which can cause distortion or noise in the same colors. Black LEDs have more stable and softer colors, although less bright than white LEDs.

Contrast Ratio: GOB LED Display VS SMD LED Display

LED Display Contrast Ratio: COB VS GOB

The contrast ratio of the COB led screen is higher than the SMD and GOB led screens. This is because the COB package does not use a bracket structure to support the chip device, which limits the size of the package body and the light-emitting pixel point. The COB package can use smaller chips according to different viewing needs, which increases the black area on the display and improves the contrast.

cob-led-display-visionpi-painting high contrast ratio copy

LED Display contrast ratio Flip chip COB vs Lateral Chip COB

The LED display contrast ratio of the flip-chip is higher than the front-mounted chip. This is because the flip-chip does not have electrodes and bonding wires on the light surface, which occupy part of the area that should be light. The flip-chip also has a larger light-emitting area and a higher luminous efficiency. This makes the LED brighter when it is on and darker when it is off, which enhances the contrast.

High Contrast COB LED Display

As aforementioned, the importance of high contrast for mini LED displays is obvious. The combination of full flip-chip and COB packaging technology of the mini LED display is an outstanding contribution to improving the contrast. Therefore, a full flip-chip COB display will be the best solution for a high-contrast ultra-fine-pitch LED display.

With several years of experience as the leading mini LED display manufacturer in China, VISIONPI offers COB LED displays with high contrast, high brightness, high color, high definition, and other excellent performance. For instance, our COB series displays have achieved a contrast ratio of 15,000:1 while offering affordable prices. Therefore, our COB series mini LED displays can showcase unparalleled display effects to enrich users’ viewing experience.

Pixel pitch covers P0.4-P1.8 to meet different requirements of users

1,200nits brightness
18Bit grayscale
up to100,000:1 contrast ratio
120% NTSC color gamut
7,680Hz refresh rate
Extremely high protection performance
Single Module Calibration Technology
onforms to industry standards and specifications
Self-developed optical display technology greatly protects the eyes
Multi-scene applicability

High Contrast Outdoor LED Display

The high contrast outdoor LED display designed to perform under direct sunlight incorporates features that optimize visibility and readability, even in challenging lighting conditions. Here’s a closer look at why black LED technology stands out and how it contributes to enhancing display performance in outdoor settings:

Outdoor Black LED Display Advantages

1. Higher Contrast Ratio: By using black LEDs, the display achieves a much darker black than traditional white or grey LEDs. This results in a significantly higher contrast ratio.

2. Sunlight Readability: Traditional LED displays can become washed out under direct sunlight due to their inability to produce true black colors, reducing their contrast.Black LEDs maintain their color integrity and contrast even in bright conditions. The deep blacks create a stark difference against the colored pixels, making the content more readable.

3. Lower Brightness Required:Traditional LEDs often require higher brightness levels to improve visibility in sunlight, consuming more energy.With black LEDs, the need for excessive brightness is reduced, lowering energy consumption while maintaining visibility.

high contrast outdoor led display black led

Black LED Rental Display

The superior visual performance of our Black Rental LED Display, designed to enhance contrast ratios and minimize reflections in any lighting condition. Featuring advanced black LED technology, this display excels in both outdoor and indoor environments, making it an ideal choice for broadcasting, filming, and live events. Under sunlight, its visibility surpasses traditional displays due to its exceptional contrast levels, even outperforming many indoor LED displays. Additionally, the wide color gamut covers 99.9% of DCI P3, ensuring rich, vivid colors that bring camera captures to life with stunning clarity and depth. Whether for an event, broadcast, or filming project, our Black Rental LED Display offers unmatched visual quality that adapts flawlessly to every environment.

black led for rental led display indoor and outdoor

How to Remove Moisture from LED Display

Mar 24, 2021 | ledtips | 0 comments

HANDLE MOISTURE IN LED

How Does Moisture Damage led display

Water can cause many problems with the performance and reliability of electronic devices. It is estimated that one in five electronic devices suffers from moisture-induced corrosion worldwide. Moisture can also affect the quality, lifespan, and user experience of LED displays by causing abnormal-luminous LED pixel columns and dead pixels.

Moisture can damage your LED video wall by harming the critical components, such as lamps and IC. These components are sensitive to moisture and can short-circuit or malfunction. This can lead to LED caterpillar failure, which is when some LED pixels light up randomly or not at all. This usually happens during the wet season, in high-humidity environments, or after a long period of inactivity.

What is dehumidification?

Dehumidification is a service that can help you protect your LED module(s) from moisture damage. It works by displaying a dark screen and gradually changing it to a lighter screen. This way, the circuitry heats up slowly and removes the humidity. The whole process takes about 70 minutes.

Humidity can shorten the lifespan of your LED display, so using this service can prevent that. You should use this service when your LED display has been exposed to a high-humidity environment. See “When should dehumidification be done for my dvLED?” for more details. You should also avoid using your LED display in a humid environment for too long.

When an LED screen is not in use, the LEDs will start absorbing moisture from the air, no matter if it is an indoor or outdoor screen. The longer the time and the higher the humidity of the air, the more moisture will be absorbed by the LED. When the LED contains moisture, there is a risk of damaging the LED when the LED heats up too aggressively.

When to take Dehumidification?

being installed for the first time,
in a rainy season, a snowy season, and/or in a coastal area,
un-used for a long time (3+ months)

Therefore, VISIONPI recommends that if you have not used a screen for a prolonged time and/or the screen was stored in a very humid environment, you slowly heat up the screen. In our manuals, we have a 12-step recommendation for heating up the screen (and thus drying out the LEDs):

“The moisture needs time to evaporate and come out of the LED”

How to handle moisture in LED screens

Basically the slower you ramp up and the longer time you spend at each step, the better. The moisture needs time to evaporate and come out of the LED. In case it is not possible to follow the above schedule, any reduced form of the above schedule is better than not doing anything at all.

One extreme example of a reduced schedule is when you would first power the screen up on site when the wall has just been built. Don’t immediately put it at 100%, but start at a lower brightness and gradually increase it. With this recommendation, we hope to have helped you keep your products healthy.

Intelligent Dehumidification

Intelligent Dehumidification Technology can also help to get the moisture out during daily use of the LED screens. Three dehumidification modes are set to dehumidify the video wall based on measurements of a variety of complex environments and the unused duration of the LED wall. Simply run the current-gain dehumidification program automatically or manually to easily complete the dehumidification maintenance of your LED video wall.

COB LED VS Mini LED

Mar 25, 2019 | General | 0 comments

The packaging technology of LED display modules can be divided into two types, one is SMD (Surface Mounted Devices) and the other one is COB (Chip On Board). 4in1 LED is still a number of SMD. The comparisons of these two products are as follows:

I. Production Cost: As compared to the flip-chip COB module, the 4in1 LED module has more production workstations (as shown in the picture below), which increases production cost. In addition, the flip-chip COB module adopts the mass transfer method to set LEDs on PCB boards; however, the 4in1 LED module applies the traditional single-chip per transfer method to set LEDs on PCB board one-by-one. Thus, the production capacity is ten to hundred times different. The cost advantage of flip-chip COB module may help speeding up the construction and expansion of virtual production environments.

As compared to the flip-chip COB module, the 4in1 LED module has more production workstations

II. Display Performance: In terms of display performance, the area of the Flip-Chip is smaller on the PCB board, and the duty cycle of the substrate is increased. It has a larger light-emitting area, which can present a darker black field, higher brightness, and higher contrast.COB LEDs are precisely placed on PCB boards so that the flatness and accuracy of the module are outstanding. Moreover, the viewing angle of the flip-chip COB module is around 175°, which is wider than the 160° viewing angle of the 4in1 LED module, and there is no pixel granularity on the flip-chip COB module. In addition, the flip-chip COB module can effectively suppress the moiré effect.

III. Product Reliability: Flip-Chip COB can achieve true chip-level spacing, reaching the level of Micro LED. This is because, from the perspective of the LED chip, the Flip-Chip does not require wire bonding, which breaks the pixel pitch limit of the formal chip and solves the problem of metal migration in the formal LED.
LED surface of the flip-chip COB module is packaged with an integral epoxy resin mold to avoid oxidation; the exposed solder joints of the 4in1 LED module are susceptible to interference by water and oxygen.

Please refer to the following comparison table of product reliability. Comparing the various characteristics, the overall reliability of the flip-chip COB module is much better. It is more suitable for the film and TV industry that requires frequent disassembly and assembly of LED modules.

In summary, from the perspective of production cost, display performance and product reliability, the flip-chip COB module is significantly better than the 4in1 LED module. As an upgraded product of formal COB, flip-chip COB is based on the advantages of formal COB ultra-small dot pitch, high reliability, and non-glaring surface light source. Further, improve the reliability, simplify the production process, better display effect, perfect near-screen experience, and real chip-level spacing can be realized.

Thesaurus of led display technology

Mar 24, 2018 | ledtips | 1 comment

LED PIXEL PITCH

LED display resolution

The number of distinct pixels in the respective dimension that can be displayed, generally mentioned as pixel per width × height, is the LED display resolution.

Pixel pitch

Pixel pitch is the distance from the center of an LED cluster (or pixel) to the center of the next LED cluster/pixel measured in millimeters. This is not necessarily the same as the pixel size, which refers to the size of an individual pixel. The shorter the viewing distance (closer shooting distance) the smaller pixel pitch is required.

Driver IC

The driver IC will control the LED. It will generate the PWM signals to have the LEDs display the required brightness. The modern driver IC’s use many advanced technologies to get the best possible performance out of the LED.

Receiving card

The receiver card is the link between the LED processor (with video input) and the driver ICs (connected to the LEDs, video output). Except for decoding and distributing the video signal, the Receiver card will do a lot of extra corrections, such as brightness, gamma, calibration, etc.

Color gamut

Color gamut is “the color triangle”. The larger the surface you can cover in this triangle with your LED panel, the more colors you can show.

Refresh rate

Refresh rate is how many times per second a frame is redrawn on the display. (Typically, 1920, 3840, 7680Hz)

Scan rate

Scan rate, also named scan mux or multiplexing. One driver IC output pin drives multiple LEDs. This is done by completing the circuit for each LED one by one (multiplexing). During one refresh cycle, all the LEDs will light up once. Typical scan rates are 16:1, 11:1, 8:1.

Contrast

Contrast is the difference in luminance or color that makes an object (or its representation in an image or display) distinguishable.

Frame rate

Frame rate is the number of frames per second. This is typically determined by the video source. (Typically, 24, 50, 60Hz)

Scan lines

Scan lines is the effect your eyes or the camera pick up when the refresh rate is too low. A camera is more sensitive than our eyes to pick up scanlines. Typically higher refresh rates are desirable and genlocking (synching) the refresh rates between the screen and camera may be needed.

Are microLEDs the next big thing for display technology?

Mar 1, 2018 | knowledgebase | 1 comment

Are microLEDs the next big thing for display technology?

Sized to be individual display pixels, microLEDs are under heavy development, with emphasis on singulating, packaging, and assembling these LEDs into displays.

What is a microLED?

The term microLED typically refers to the size of the emitting area of the LED device. However, there is no clear industry clarity on the size that qualifies as “micro”—and the definition can vary based on the application. For example, for virtual-reality and augmented-reality(AV/VR) glasses, the desire is to have microLED elements that are smaller than 10 μm. For direct-view displays, some like the definition to be 50 or 100 μm. Above this size is a new category called miniLED; again, no clear emitter size range has been agreed to.

To make things even more confusing, many display companies are simply calling their latest very-fine-pitch display pixels “microLEDs” regardless of the size of the emitter being used. This is because for a display device, it is the pixel pitch (the space between full-color pixels) that is more important than the LED emitter size.

The most-familiar type of direct-view LED (DV-LED) display is a so-called “videowall.” These are modular displays made from a number of “cabinets,” with each cabinet composed of several “modules.” Each module in turn has red, green, and blue(RGB)LEDs mounted on a circuit substrate along with drivers and electrical interconnections.

Over the last few years, there has been a clear trend toward narrow- or fine-pitch LED video walls. These are generally defined as pixel pitches of under 1.5 mm, with the latest prototypes now at 0.4 mm. Such displays are designed for closer viewing distances. For perspective, 0.4 mm is very close to the pixel pitch on a 65 in. 4K-UHD resolution TV. As a result, major TV brands are very interested in this technology.

DV-LED displays can meet and often exceed LCD or OLED performance in terms of luminance, dynamic range, color gamut, viewing angle, black levels, and so on. The main disadvantage is price. One of the main cost drivers for DV-LED displays are the RGB LEDs. Moving to smaller LED emitters mean less LED device material is needed—a substantial cost reduction. The other major cost factor is the packaging of the LEDs and assembly onto the module circuit boards.

Historically, LEDs are diced from the epitaxial wafer, placed in a surface-mount package, wire-bonded in place, and encapsulated with epoxy or silicon (so-called SMD top LED). Variations in the way these LEDs are assembled on the printed circuit board (PCB) can be described as glue on board (GOB) and adhesive on board (AOB). Several newer approaches seek to reduce costs and allow smaller pixel pitches. These can be described as SMD chip LED, integrated matrix devices (IMDs), and chip on board (COB). A photo of the small-scale demo along with a table describing the configurations and strengths/weaknesses of each are shown as below:

However, it is likely that they are in the range of 100 to 300 μm in length or diameter, so either microLED or miniLED, depending on the microLED definition.

At ISE, Visionpi (Shenzhen, China) showed a state-of-the-art 0.4-mm-pitch DV-LED microLED video wall. This is a flip-chip COB approach probably to a PCB backplane. This prototype is a single-chip solution.

Note that the distance between each RGB set of LEDs is 0.4 mm, so the active LED diameter is around 70 μm, which is below the 100 μm microLED threshold that some use as a definition. Also note that as the active LED area gets smaller, the surrounding black area gets larger. This creates a display with a better black level and higher contrast. Sony’s Crystal LED video wall has a pixel pitch of 1.2 mm with emitters that are thought to be about 100 × 35 μm in size, leading to a display with 99% of the area being black with really great performance.

Visionpi is a company that offers display solutions to its mainly rental and staging customers. Their showcase at ISE was designed to help illustrate the difference in image quality one gets with these different packaging and manufacturing approaches. Visionpi uses a single flip-chip approach overcoated with a thin layer of adhesive silicon and black adhesive between the flip-chip devices. This display uses microLEDs with a pixel pitch of 0.83 mm and has a luminance of 2000 nits.

TV brands are also very interested in microLED technology. At CES 2020 (January 7-10; Las Vegas, NV), Samsung expanded its line of microLED-based displays called “The Wall,” while others exhibited various prototypes that they hope to bring to market in 2020 (see Table 2).

Challenges remain for all these technologies, which impacts their high costs. For example, most DV-LED displays still wire-bond the LED inside the package or to the PCB. Flip-chip devices eliminate all the wire bonding, but require that the surface of the LED epiwafer be planarized so the n and p contacts are at the same level. The device can then be flipped over to directly solder to the PCB.

Wire-bonded multi-in-one IMD devices are available today, as are single flip-chip LEDs, but they are not yet very common. IMD flip-chip devices are still only available as prototypes.

Singulating the individual die or IMD devices also has its issues, too. When a laser is used to separate the die, it can leave rough edges that reduce the black level. Overcoats of epoxy can also have thickness variations leading to variations in black level over the display. In addition, bad LEDs need to be removed and replaced in the manufacturing process, which can vary from doable to nearly impossible.

As Lucas. W, Director of LED & Displays at visionpi, noted, “Each LED videowall supplier working on COB has some unique processes to optimize cost and performance parameters. The reality is that some have optimized one set of parameters and another a different set, but none have optimized all just yet. However, the fact that most of them can be solved already makes us confident for the future of COB.”

Developing next-generation microLED manufacturing

One fundamental issue with DV-LED displays is that the LED pitch on the epiwafer is very small, while the pitch on the DV-LED display can vary widely. Current mass transfer methods can transfer one to dozens of LED chips at once. To truly become cost-competitive with LCD or OLED displays, the transfer rate must increase to millions per minute. As a result, this is where a lot of innovation is concentrated now.

The most-common approach is a stamp transfer that can pick up thousands of microLEDs at a time and transfer them to a separate substrate with a different pixel pitch. Another approach uses laser pulses to transfer LEDs from a carrier substrate to the display substrate. Few details about these and other approaches are ever revealed, as they are considered proprietary intellectual property.

The next problem to worry about is yield. Not only must the mass transfer be extremely fast, but placement must be very accurate. As the size of the microLED gets smaller and smaller, the ability to pick up and accurately place it becomes more and more difficult. If a defect is found, is there a repair process that does not take far longer to complete than the initial mass transfer time? And this just applies to mechanical/electrical yield.

All the LEDs must also fall within a certain range of luminance and wavelength to provide the kind of performance demanded by end users. This is pushing the LED wafer makers to improve the way the LEDs are fabricated. New MOCVD chambers with much better uniformity and layer control are now available to enable most of the wafer to fall within quality control guidelines. Traditional gallium nitride (GaN)-based blue and green LEDs are grown on sapphire epiwafers with a 2 to 6 in. substrate size. To lower costs, larger wafer sizes are desirable. Consequently, GaN-on-silicon epiwafers are also being used to grow green and blue microLEDs at 8 in. sizes now, with the potential to go to 12 in. wafers later.

Many of these requirements point to the need to have a way to fully characterize the microLEDs at the wafer level prior to any mass transfer method. Companies are working on this need as well.

All these LEDs also need to be driven with signal to create an image. DV-LEDs mount the LEDs on a PCB and use a lot of driver chips to send signals, and next-generation DV-LEDs may well be mounted on glass substrates with active-matrix driving using TFTs at each pixel location. This will provide better control of each microLED and can leverage the TFT-on-glass fabrication infrastructure already in place for LCD displays.

Finally, since the display needs RGB LEDs, all the above improvements and techniques must be done three times for the RGB wafers.

LED Display Contrast Ratio Definition

Static and dynamic contrast ratio

Different Contrast ratios Among COB, GOB, SMD led displays

SMD LED Display: Black SMD LEDs VS White LED Screen.

Contrast Ratio: GOB LED Display VS SMD LED Display

LED Display Contrast Ratio: COB VS GOB

LED Display contrast ratio Flip chip COB vs Lateral Chip COB

High Contrast COB LED Display

High Contrast Outdoor LED Display

Black LED Rental Display

How Does Moisture Damage led display

What is dehumidification?

When to take Dehumidification?

Intelligent Dehumidification

LED display resolution

Pixel pitch

Driver IC

Receiving card

Color gamut

Refresh rate

Scan rate

Contrast

Frame rate

Scan lines

Are microLEDs the next big thing for display technology?

Developing next-generation microLED manufacturing

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