Allowable number of dead pixels
TV manufacturers from little-known brands to well-known brands Samsung and LG are guided by generally accepted quality standards ISO 13406-2. The document regulates such parameters as the level of brightness, contrast, degree of screen reflection, readability of text information, uniformity of backlighting, color and fill, and other characteristics. It also defines the quantitative values of defective points that are allowed in the screen matrix, depending on the classification. According to this document, all produced screens are subdivided into classes.
Most of the TVs on the market are equipped with screens of the 2nd and 3rd class. These are devices of the mid-price and budget segments. Premium class models are equipped with class 1 screens. TVs are expensive and inaccessible to the mass consumer. Monitors of the 4th class are not used in mass production of TV-receivers.
Using test pictures
To do this, you need to write a set of one-color test pictures to a USB drive in advance and use them to identify image defects. The verification mechanism consists in sequential display of single-color images of blue, green, black and white colors from a flash drive. It is required to carefully examine the screen in each color to see defects in the form of white, black and colored dots.
Broken pixels: how to identify defects when buying a TV
Buying a modern TV receiver or monitor is a costly event for the family budget. The choice of a high-quality digital device is especially important for the buyer, so as not to waste time and nerves later on returning, exchange or warranty repairs.
When buying, it is worth checking the TV matrix for operability and identifying the presence of dead pixels. In this case, the buyer needs to take into account an important nuance that does not fall under the concept of marriage, but at the same time affects the image quality. How not to bring home a TV panel with dead pixels.
How to check your TV screen for picture defects
Some outlets provide a screen check for matrix defects on a paid basis. With some knowledge, you can determine the dead pixels on the TV yourself. There are two options for checking, both are described below.
What are dead pixels
A pixel or luminous point is a key element in the construction of the screen matrix. An important parameter of image formation is determined from the number of pixels per inch. resolution. In LCD and LED TVs, pixels are realized in the form of liquid microcrystals, illuminated from behind or from the side. To obtain a color image in each cell of the matrix there are RGB filters, the so-called subpixels.
When not in use, the cells of the TV screen are opaque. Under the influence of an electric current, the orientation of the crystals changes towards one or another degree of transparency. Light transmitted through RGB matrix filters draws a color image on the screen. In the process of image formation, defects may occur, characterized by the appearance on the screen of individual dots that are knocked out of the overall picture. This phenomenon is called dead pixels.
Depending on the color of problem points on the monitor, broken pixels are divided into the following types.
- Hot pixels appear as white dots on the screen. The issue is caused by a glitch in the control of the RGB filters of the cell, when all three subpixels are constantly open and allow 100% of light to pass through.
- “Dead pixels”, otherwise called “dead”, are characterized by the appearance of individual black dots on the monitor. The problem is caused by insensitivity of the crystals to light, or a failure in the supply of electrical impulses.
- Stuck pixels appear as colored dots that do not change when the picture changes. A defect is caused when the crystal solidifies in a semitransparent state.
The figure clearly demonstrates the appearance on the screen of “hot”, “extinct” and “stuck” pixels from left to right, respectively.
Is it possible to recover dead pixels
You can try to get rid of defects of the 3rd type found during operation (stuck / stuck colored dots). There are two ways to remove dead pixels on your TV. Both methods, as practice shows, give a short-term result, moreover, careless actions are fraught with damage to neighboring cells.
- Through the program. The effect of the utility is to change the colors of each pixel at a high speed within a certain period of time (10-20 minutes or more), which makes it possible to return the frozen pixel to work. Special programs for such manipulations are Bad Crystal or JscreenFix, but they are paid.
- Mechanical impact. Turning off the TV, you need to use soft circular motions with a cotton swab in the defective area to try to make the frozen pixel work.
Advice! Do not hope that individual dead pixels can be recovered. The best option is to check your TV before you pay. This approach will help avoid potential problems with returns and repairs.
What pixel defects are there
Any abnormal pixels visible against the general background are called broken, but this is not entirely correct. Really broken or dead pixels are only those in which the transistor is out of order. They do not glow with any color and just remain black, falling out of the matrix grid. Clearly visible on a white background.
Hanging pixels on the left and right, broken ones in the center / digital-boom.ru
There are also frozen or stuck pixels. these are red, green, blue or white dots that are clearly visible on a black background. They occur when subpixels are stuck on a color update.
How to check a monitor or TV for dead pixels and get rid of the problem
You will need a free app, a Q-tip, and a little patience.
How to check the display
You can visually determine the absence of defective pixels upon close examination on a solid white, black, red, green and blue background. To do this, you need to download such pictures to a USB flash drive and play them on the device you like. If none of the dots are out of the general color, then everything is in order with the screen.
Another option is to use special software if you can run it. In fact, these are the same color pictures, but in a more convenient format for applications or online services.
- Dead Pixel Tester is a simple open source utility for Windows. After starting, you need to select a mode and carefully look at the screen.
- InjuredPixels is another free Windows app. Colors are switched by mouse or using arrows.
- Dead Pixel Buddy is an online color checker tool. Works in any browser, including mobile ones. Don’t forget to enable full screen mode.
- LCD DeadPixel Test is another online service. Choose a color, expand the window to full screen and check.
What are dead pixels
In all LCDs, the image is formed from a grid of pixels. They are made up of three separate subpixels in red, green and blue, which are responsible for full color image formation. Each subpixel has a transistor that controls it on and off.
It looks like a broken pixel on the screen / overclock.net
Even the matrix of a conventional HD monitor contains over 6 million subpixels, and in 4K displays their number reaches 37 million. With such a huge number, some of the transistors can malfunction. Then certain subpixels remain on or, conversely, off.
The method consists in the cyclic output of rapidly changing images, which, due to frequent color changes, increase the chance of returning the hung pixels to the ability to switch again.
There are many options for implementing this method through utilities, online services, and even YouTube videos. They can be used on a computer as well as on a TV when connecting a PC with an HDMI cable.
- Bad Pixel is a professional paid utility for Windows, the creators of which promise to remove defective pixels in just 10 minutes.
- DeadPix is a universal program for Windows and Android that helps you find and then fix problem pixels using color cycling.
- PixelHealer is another utility for Windows. Eliminates stuck pixels by fast flickering RGB colors.
- JScreenFix is an online service to run on computer, TV and mobile devices. Outputs an area with digital noise that can be moved to the desired area of the screen.
- PixelFixel is a 12-hour YouTube video that is suggested to run and leave overnight. Attention! The colors in the video change at a very high rate and can cause an epileptic seizure. Do not look at the screen, but rather turn it to the side.
How many dead pixels are allowed
It seems logical to replace a computer monitor or TV with dead pixels, but manufacturers do not consider the latter to be a factory defect. When you contact the service with such a complaint, you will most likely be denied service.
Dell Dead Pixel Policy / dell.com
Different suppliers have their own standards for the number of defective pixels, depending on their location, resolution and display diagonal. So, LG considers up to 10 stuck and 3 broken pixels on 20-inch screens to be the norm. Samsung has 7 dead pixels for monitors, while Dell has 1–6 stuck and 6–13 bit pixels, depending on the line of displays.
How to remove dead pixels
Since black pixels are the result of damage to the transistor, they cannot be repaired without replacing these components. And this is almost unrealistic even in laboratory conditions. The situation is different with colored dots, which appear due to freezing of subpixels. You can try to remove them.
How to check your TV for dead pixels yourself
The buyer in the salon can himself test the matrix for defects. Such a procedure is provided for at the legislative level. If the seller-consultant denies the possibility of inspection, insists on paying for the inspection service, it is better to refuse to purchase at this outlet.
To carry out the test, you must prepare a USB flash drive in advance by throwing on it monochrome pictures of black, white, green, blue, red, or 4K videos for checking TV, capable of showing the operation of the LED panel:
Before testing, the TV must work for a few minutes, since defects appear only on a warmed-up screen. If there is a defect on the screen, it will be noticeable when checking.
When buying a Smart TV, you can do without a flash drive, just install a tester application (among popular programs for Android: Dead Pixel Detector Fixer, Screen Check, Dead Pixel Test), or go to a website that provides such services (for example, Dead Pixel Buddy, where 9 high-resolution color images are presented, or LCD DeadPixelTest, where the pictures are conveniently located by links).
- connect a TV to it via an HDMI cable;
- open a website or an application (for example, Dead Pixel Tester, available for free for Windows 7,8,10);
- view pictures, videos to determine the presence of burnt zones.
How to recover
It happens that the TV is bought, and a dead pixel is revealed at home. Also, the presence of a marriage can manifest itself during operation.
In such a situation, you can try to fix the problem (you can restore performance only when the dot glows in color), but the presented methods are considered insufficiently effective. The defect often returns after a few days of viewing.
Does the warranty cover
Matrix is a panel that requires complex, time-consuming production. The defect can only be identified after the TV is fully assembled.
If the manufacturer eliminated all defective panels, even with one defective pixel, the cost of the panels would increase significantly. Therefore, a compromise solution was spelled out in the standard:
When the presence of dead pixels is recognized as a defect
The permissible number of dead pixels on a new LCD panel is determined by the international standard ISO 13406-2.
The document describes the normal operating parameters of the display. So, the standard defines 3 types of dead pixels:
- open. highlighted in white, cannot be restored;
- closed. black dots to be repaired in a service center;
- colored. a broken pixel glows with a red, blue, green tint, which indicates a breakdown of the transistor.
Most manufacturers divide matrices into four segments:
- there should be no dead pixels in class A. This technique belongs to the premium class;
- category B allows from 2 to 4 black dots, up to 5 colored dots per million;
- in class C, a TV is not considered defective if there are up to 5 black, 15 white and 50 color pix. Such matrices are typical for state employees;
- category D. devices with up to 700 defective points. Such TVs are practically not found on sale.
There are a number of free and paid apps available to fix the flaw. Among the popular ones:
- Bad Pixel. According to the developer, the program helps in 90% of cases. Offered for a fee.
- PixelFixel. Activates a video sequence that changes colors on the panel for 12 hours. Active influence helps to activate the transistor.
- DeadPix. A program for a computer, smartphone that can bring a broken point back to life.
- JScreenFix. A specialized site where the screen is configured online, while the user can indicate the damaged zone, start the recovery process.
How dead pixels affect the image
Pixel. the point from which the image is formed on the screen. A separately taken unit consists of three subpixels: green, red, blue. A transistor is responsible for each, turning on or off one of the colors on command.
In the simple model, the matrix consists of more than 6 million subpixels, and in the new panels that support the 4K format, their number can go up to 37 million. With this indicator, the probability that several transistors will fail is high.
By applying physical effort to the damaged area, you can restore the contact between the diode and the transistor. To do this, gently massage the area around the broken pixel with a leaf. In this case, manipulations should be carried out with the TV off, the desired place is determined in advance.
After making circular motions, there is a chance that the point will work. The main thing is not to overdo it, as you can damage other pixels, exacerbating the situation.
We use software. For this, applications are used, there are both free publicly available and paid ones.
- Bad pixel.
The program is paid, but the developers claim that after launching it, you can eliminate up to 90% of all defects on the screen in a few minutes.
A video in which colors change at high speed for 12 hours. It is recommended to turn it on at night, but you cannot look at the screen as there is a possibility of causing an epileptic seizure.
A universal program that can be installed on both a computer and a smartphone. The site has a detailed video instruction for installation and configuration.
The site on which you can run the setting online. You can manually specify the damaged area of the screen and start treatment.
How to recover
But what to do if the TV has already been purchased and during the testing process they found a broken pixel, what to do in such a situation, we will figure it out further. Pixels can also be damaged as you use the TV. Immediately, we note that only colored dots can be normalized. However, their serviceability is only a temporary phenomenon. After a few days, the defect will appear again.
Types of defects and how many are allowed
The permissible number of dead pixels on a new TV is strictly regulated by the international standard ISO 13406-2. The document is quite voluminous, it describes in detail all aspects of the screen. over, there are 3 categories of damaged points in it:
- Open. permanently glows white, cannot be restored.
- Closed. dead pixels, always black, can be repaired, but in a service center.
- Colored. the breakdown lies in the control transistor, as a result, the pixel glows in one of the following colors. blue, red, green.
With the help of special software, you can deal with the problem at home. In Samsung, and many other well-known companies, TVs are divided into four classes. Most of the produced TVs are of the second class. First class devices shouldn’t have any defective points at all.
Checking the TV for dead pixels. How to fix a defect
We put in physical effort. In this case, you need to gently massage the damaged area with a cotton swab or eraser on a pencil. To do this, we find all the defective points, turn off the TV and make circular movements in the right place. However, even doing everything correctly, the desired result may not be achieved, but it is quite possible to damage neighboring elements.
How to remove dots manually
What is a dead pixel
First you need to figure out what a pixel is on a TV screen or computer monitor. A pixel is a kind of grid of cells that form an image. Each pixel is made up of three subpixels. red, green and blue. Each color is controlled by a separate transistor, which at a certain point in time turns it on or off, thereby creating the picture that we see.
Even the simplest display consists of at least six million subpixels, and in 4K displays their number can go up to 37 million. Such a number of transistors can fail, then any of them, when you need to turn on, it turns off. and vice versa. A dot appears on the screen that stands out noticeably. this is a dead pixel.
How to check yourself
For the test, you will need a regular flash drive, you need to throw off monophonic images on it. white, black, green, etc. You need to start checking after the TV has been running for several minutes, since defects appear only on a heated matrix.
To start checking for dead pixels on the TV when buying, ask the seller to insert a previously prepared USB flash drive into the TV. Then display the images. So, on a white screen, dark pixels will be clearly visible, and on a black one you can see white dots.
Special testing programs are also available. There are a lot of them, but most often they are used:
- Dead Pixel Tester.
Free application for a computer on Windows 7,8,10. The site also contains detailed instructions for checking, which is very convenient.
- Dead pixel buddy.
A site that has 9 color pictures that can be opened in full screen both on a TV / computer and on your mobile phone.
Another program with many settings and high resolution pictures for tests.
- LCD DeadPixelTest.
The easiest site to use. Everything is very simple, there are names of pictures, click on each of them and make it full screen.
In terms of application, the second application is simpler, and it was developed specifically for testing LCD screens. Illuminates any area of the display in the desired shade. As a result, all defects can be quickly detected.
If you do not know how to check the TV using these programs, follow the instructions on how to connect a laptop to a TV. By doing this, you will be able to transfer the image from the computer to the TV screen.
Why not a warranty case
In general, a certain number of dead pixels are allowed. This is explained by the fact that the matrices are quite complex and laborious in production. Few manufacturers are able to provide it. However, it is possible to identify the defect when the TV is in a fully assembled state. If manufacturers filter out all products with a defect, even an insignificant one, then the cost of TVs will increase significantly. Therefore, a balanced decision was made:
- all companies that produce TVs maintain the production at the proper level, but do not increase the cost either;
- buyers agree to the presence of dead pixels, but have the right to test the display before purchasing.
There is no cheating, the buyer has every right to check the purchased device. If he didn’t, he can only take offense at himself.
How to check
To check the screen for defects, you need to consistently submit pictures of the primary colors to it, and at the same time carefully look at it, trying to find points of a different color. This is what broken pixels look like. For example, when there is a white picture on the screen, it is easy to detect black and colored dots. If the color is black, then it is easy to find white dots, etc. Before the test, with the TV turned off, make sure there are no dust particles or other debris on the screen.
How many dead pixels are acceptable? The answer to this question is contained in the international quality standard for LCD TVs ISO 13406-2. It identifies 3 types of defective points:
- Open or white. such pixels freeze in the open state and constantly glow white.
- Closed or black. such pixels freeze when closed and constantly glow black.
- Colored. the control transistor of such pixels fails, and they are constantly lit in one of 3 colors: red, green or blue.
Also LCD devices are divided into 4 classes. The first class is the highest, the presence of defective points is generally not allowed in the matrix of devices of this class. The bulk of the devices on the market are of the second class. The standard defines the allowable number of different types of defective dots depending on the maximum resolution it supports. Information for popular 2nd class devices is shown in the table below.
|pixel type \ max resolution||1280 × 720 (720p, HD Ready)||1920 × 1080 (1080p, Full HD)|
Test the screen for dead pixels yourself
When buying a TV or monitor, sellers offer to use an additional service. check for dead pixels. over, the service is paid and higher. If you find a defect at home, you will no longer be able to return the TV back, they explain. After all, this is not a guarantee case, and they are right. In fact, you can perform such a matrix test yourself and for free, there is nothing complicated about it. It is enough just to bring a special video or pictures with you on a flash drive for verification, having read our article before.
Why are some dead pixels allowed? The fact is that the technology for the production of LCD matrixes is very complex, and not even every device manufacturer can afford their own production. And such a defect can only be detected on the assembled device. If the manufacturer scraps screens even with minor defects, then the price of TVs and monitors will increase several times. Therefore, such a compromise was found:
- Manufacturers keep production at the same level and do not raise prices.
- Buyers allow the presence of a certain number of dead pixels, which is not a warranty case. In this case, the buyer has the right to check the display before purchasing.
- Programmatic approach. A matrix picture is fed to the screen, in which dots of different colors are randomly displayed. Within 20 minutes, the problem pixel should be restored;
- Mechanical approach. Turn off the TV, press the broken pixel with your finger through the napkin, turn on the device and stop pressing. This method can harm the matrix.
External inspection upon purchase
First, check the packaging for various damages (dents, breaks), if during transportation there were any blows to the packaging, then the TV got it. Then you check the availability of all correctly completed documents, such as a passport for the device, a warranty card. The coupon must be filled out correctly by the seller (warranty period, date of sale, stamp), the serial number on the coupon must match the number on the TV.
Check the external condition of the TV and the remote control. Look for scuffs, chips, cracks, etc. The screws on the back of the TV must not be tampered with, otherwise your TV was already on sale and being repaired.
By the model name, serial number and product code, you can find out where and when this TV was made and for which country.
After that, you can turn on the TV and check its operation. correct operation of the remote control, work with external sources (USB flash drives, players, etc.). You can take your own flash drive by pre-recording high-resolution videos on it, and pictures to check for dead pixels.
Check for dead pixels
When forming a picture on the TV screen, all display pixels must be involved. With a Full HD screen resolution, the entire display field consists of 1920 × 1080 pixels, which is just over 2 million points.
According to the rules, a certain number of non-working pixels is allowed, different norms allow a different number of defective pixels. So, having identified this defect at home in the form of one or two non-working pixels, you will not be able to return the TV back, so it is better to do this check before buying.
To search for defective pixels on the screen, you need to submit an image with a specific picture and examine the screen from a close distance. You can also use a magnifying glass. You need to look for a pixel that glows in a different color from all the others. The image must match the screen resolution exactly.
Completely inoperative pixels, those that do not respond to the signal and are in a constant position, can be found in a uniform picture (filled with one color). White, black and primary colors (red, blue, green) pictures are alternately fed to the screen and pixels of a different color are looked for on them.
Inoperative pixel on black background Inoperative sub-pixel on screen
There are some defective pixels that start to work poorly when the matrix heats up. You can identify them after the TV has been running for a while.
There are pixels that do not work correctly depending on the work of neighboring sub-pixels. You can find such defects if you present a picture on the screen in the form of a checkerboard fill, color stripes, gradations, a grid. Incorrectly working pixels will stand out from the general structure of the picture.
The necessary pictures for checking the picture on the TV can be downloaded here. Resolution of verification images 1920 x 1080 pixels.
To test Ultra HD 4K TVs test pictures here.
How to use these images can be read here.
Non-uniform screen illumination
When a video signal with a uniform color fill (painted in one color) is input to the TV input, this color should be on the screen without any color shades. But, due to the technological peculiarities of manufacturing displays with LED backlight, such a uniform illumination is difficult to achieve. Therefore, it is advisable to check the uniformity of the color field before purchasing. Usually such a defect is not considered a breakdown and the TV cannot be returned or repaired.
Such screen defects are called banding, flashing and tint.
Tint can be translated as “color tone” and it shows how correctly white is displayed on the screen. When watching a regular video, you may not see this defect, because the picture is constantly changing there. But if the picture is static, then the interference can be very noticeable and interfere with normal viewing.
To identify the tint, you need to submit a white or gray field to the screen. Interference in the form of stripes, spots and other shapes, painted in a different tone, against a uniform background may indicate the presence of a defect in the tint. Such noise is usually pink or greenish in color and is located closer to the edges of the screen.
If the defect is very noticeable, then it is better to choose another TV.
The tint is large and clearly visible. Allowable interference level.
Invalid banding level
Only LED TVs can have glare. To assess the quality of the display by the level of illumination, you need to do this in a completely dark room (turn off the light and shade the windows). In this case, you need to select the maximum backlight level on the TV, for this you can select the appropriate mode (it can be called “bright”, “dynamic” or in another way). You need to disable image enhancement modes such as Dynamic Backlight, Black Level Correction, Eco Sensor, and others. This is done so that the TV does not adjust the backlight when checking.
But even so, errors may occur due to the automation of the TV receiver, when a completely black frame is fed. Indeed, with a black picture, the TV turns off the backlight. Therefore, to detect highlights, it is better to submit a black picture with some bright elements, for example, white titles on a black background at the end of the film.
Then look from a distance for screen glare, especially in the corners. Some minimal highlights are fine for normal viewing.
Invalid backlight level
Finding an LED TV completely free of these defects (tint, banding, lightning) is unlikely to work, but you need to choose a model with a minimum level of these interference.