Acceptable norm of dead pixels on TVs. Question about dead pixels. Acceptable number of defective pixels on the monitor

Dead pixels can be found in products from any manufacturer; no one is immune from defects. Be it dead pixels on a phone, on a camera display, on a TV (monitor), or on any other device equipped with a display. Therefore, before purchasing, checking for defective items comes first. The most simple option The check is to display black and white images on the screen. If there is a faulty or dead pixel, against such backgrounds they will immediately catch your eye.

At matrices LG, Panasonic, Philips, Samsung, Sharp, Sony, Thomson, Toshiba 0.3% of the total number of pixels, it is considered technically intact and cannot be exchanged or returned. That's the guarantee :)

For the buyer, one pixel is already a loss, and he wants to return/exchange the product as soon as possible, but not everything is so simple. In general, you need about 4-5 dead pixels, and then the product can be exchanged. In general, if there is at least one or a suspicion of a defective pixel, the product is not worth buying. Fortunately, nowadays there is a great choice.

You shouldn’t be lazy and you need to insist on a scheme: show the product in action - I’ll pay you money. The fact is that on LCD screens it is completely legal to have a certain number of dead pixels. And this is not considered a defect in the product.

The conclusion is that the problem is quite controversial - both sides can be understood. Another thing is that a self-respecting store will offer to look/check the product.

Acceptable number of dead pixels according to ISO 13406-2 standard.

Dead pixel values ​​on TFT monitors are defined by the international standard ISO 13406-2.
This standard defines the limit values ​​for the number of dead pixels on TFT monitors in units per million. According to it, LCD panels are divided into 4 classes depending on the number of dead pixels of different types, as indicated in the table below.

TYPE 1 – constantly glowing pixels.
TYPE 2 – permanently turned off (“dead”) pixels.
TYPE 3 – defective red, green and blue subpixels.

It should be noted that some monitor manufacturers and/or sellers give Better conditions guarantees/purchases. For example, they offer to replace the monitor if at least one “dead” pixel of any type is detected or if a group of three or more “dead” pixels are spaced together, or no further than a certain number of points from each other and/or from the center of the screen.

More

"Defective pixels"– a defect in an electronic device that receives or reproduces an image and has a pixel structure. It manifests itself in the invariance of the output signal of the digital camera matrix) of several pixels. "Hot Pixels"– a defect in which the value of the output signal has an incorrect dependence on the input signal, or the output signal is most dependent on other factors. "Dependent pixels"- a slang term meaning the dependence of a particular pixel on the value of its surroundings. Typically not noticeable in realistic images. It can only be detected on the monitor by a “checkerboard” fill or a “grid”. The reason for the appearance of such a defect is a malfunction of the matrix element, in the case of a “dead pixel” - a constant malfunction. Since manufacturing a matrix is ​​an expensive and time-consuming process, and it can be checked for malfunctions only after complete production, manufacturers try to reject products as rarely as possible, classifying them according to test results into one of the quality classes. For electronic information storage devices, the term “broken cell” is traditionally used ", "faulty cell", "faulty block", because, unlike photographic and display devices, there is no obvious connection with the location of the defect in the image.
Pixel graphics- a form of digital painting created on a computer using a raster graphics editor, where the image is edited at the pixel level, and the image resolution is so small that when viewing the image, the pixels can be distinguished by the naked eye. Older computers, Game Boy games, older console games, and many mobile phone games rely heavily on pixel graphics because it's the only way to make small images look sharp on the low-resolution screens found on these devices.

Having ordered a TV online and gone to the store to receive the goods, the consumer often forgets to check the TV for dead pixels, as a result of which he runs the risk of being disappointed in the item he just purchased when he gets home.

Since the absence of defects in the liquid crystal matrix is ​​guaranteed only by manufacturers of premium display models, the average user has to be careful and check the screen themselves before purchasing.

Pixels are the units of the LCD screen matrix, thanks to which any image is created. The main property of a pixel is its ability to change color: electricity, the amount of which is regulated by a transistor hidden in the TV, causes microelements of liquid crystals to change their location.

Thanks to the rearrangement of red, green and blue subpixels and the intensity of the backlight, one or another color is formed at a certain point on the monitor - if a TV device has 4K resolution and displays content at a speed of 30 FPS, more than 250 million such “castlings” can occur per second.

Dead pixels on a TV are the smallest elements of the display that do not change color under any conditions.

Although this defect is practically invisible to the human eye during dynamic cinematic scenes, the user may experience discomfort when viewing static images: “broken” dots stand out clearly against the general background and make it difficult to concentrate on the TV picture displayed.

Allowable number of dead pixels

Each TV manufacturer declares the acceptable level of dead pixels in the matrix - products, during a pre-sale inspection of which a number of defects exceeding the established limit were identified, should be considered defective.

Top companies such as Samsung and LG allow no more than two completely dark pixels and no more than 5 incorrectly functioning subpixels per million pixels: for example, the already mentioned 4K resolution consists of 8 million matrix units (3840x2160) and therefore can include up to 16 defective pixels and up to 40 “stuck” subpixels.

Since pixels that work properly during factory tests can fail already during the operation of the TV, the manufacturer is obliged to guarantee the full functionality of the matrix for a period regulated by international or internal requirements term.

If there are “extra” dead pixels on the TV display, the user has the right to free repair or replacement of the device.

Interestingly, the generally accepted ISO 13406-2 standard limits a company's liability to one year, while LG's Zero Bright Dot program limits it to three.

Reasons for appearance

The reason for the appearance broken points on the matrix of a color TV can become:

• overheating or hypothermia of the device. As a result of exposure to high or low temperatures, subpixels harden and lose their ability to move inside the liquid crystals;
• ambient humidity. High humidity is dangerous for the LCD substrate: when moisture gets on the matrix, illuminated areas or white dots on the display are formed;
• voltage surges. A failure in the electrical network can lead to the failure of the transistor, as a result of which the energy supplied to the RGB matrix will force the subpixels to take a fixed position;
• violation of production technology. It is worth saying that in most cases, manufacturing defects are caused by only the three factors presented above - during the production of the matrix, repeated procedures of washing, drying and lithography are carried out, the slightest non-compliance with the technological processes of which leads to defectiveness of the final product;
• using a monitor to display static content. When displaying the same picture for a long time, the display transistor may burn out and the crystals may “freeze.” Even TVs that support HDR technology (10-bit and Dolby Vision) are not immune to this problem.

Also, the matrix may be damaged during careless transportation of the TV device to the point of sale: despite the strong fixation in the substrate, liquid crystals are very sensitive to sudden mechanical shocks.

How to check your TV for dead pixels

To see broken elements of the TV matrix, it is recommended to use a special gallery of monochromatic images - there are no programs compatible with Smart-TV for checking the display.

The screen testing algorithm is presented using the example of searching for white dots:

1. Upload a special collection of images to a flash drive.
2. Connecting a removable drive to the TV via a USB interface.
3. Opening a monochromatic picture on the TV (in this case, black).
4. Inspection of the display: white broken elements should be clearly visible against a dark background.

To search for black dead pixels, you will need to use a light image, and to identify RGB defects, you will need to use any background that contrasts with the bug you are looking for.

Unfortunately, the user must rely only on the acuity of his own vision, since it is impossible to automate the described process.

External inspection upon purchase

Some resellers provide a paid service for checking the LCD display for dead pixels: the user selects a TV, and the sales consultant tests the display using images uploaded to the device.

It is worth saying that paying for such a service makes sense only if you need to check a 4K monitor, the defective pixels of which are almost invisible against the backdrop of millions of working units.

Warranty case

The service center does not have the right to refuse the consumer to exchange a defective TV for a new one only if the manufacturer violates ISO 13406-2 regulations.

The standard describes the permissible number of broken display matrix elements for a particular class of device:

You can find out the display class from the technical documentation supplied with the TV. Next we will tell you what to do if you receive a refusal from the service center.

Treatment for dead pixels on TV

Treatment of a color TV (for example, made by Samsung) from broken matrix elements at home is as follows:

• launch of a special video. You will need to download a video clip that “warms up” the matrix onto a flash drive and play this video on the TV for 40-50 minutes;
• “massage” of inoperative units. It is necessary to press on the dead pixels using a regular cotton swab - it is important to understand that if you put excessive pressure on the matrix, the final result may be the opposite of the desired one.

It is worth saying that dead pixels can be eliminated in this way on any digital technology.

Bottom line

Now you know what dead pixels are and how to check for their presence in the matrix of a new TV yourself.

It is important that the consumer has the right to free service only after the device is recognized as not conforming to the declared ISO 13406-2.

Dead pixels and subpixels on TFT matrices of monitors, laptops and TVs, unfortunately, are the norm for display manufacturers, defined by the standard ISO 13406-2

Standard ISO 13406-2 defines 4 monitor quality classes:
Class 2- the most common and allows for no more than 9 defective pixels per million pixels. Practically All manufacturers' products comply with class 2 and, if you come across a product without defective pixels, YOU ARE LUCKY! But be prepared that the luck factor decreases greatly as resolutions increase and, for example, if you buy a laptop with a WUXGA matrix without defective pixels - YOU ARE VERY VERY LUCKY! If there are 1-5 of them, you are very lucky.
Class 3- allows for the presence of no more than 70 defective ones for every million pixels of the matrix.
Class 4- the lowest, allows for the presence of no more than 700 defective ones for every million pixels of the matrix. Fortunately, to our knowledge, LCD manufacturers do not produce Class 4 monitors for sale to end users through a distribution line.
Class 1- the highest, does not allow the presence of defective pixels, but none of the manufacturers known to us corresponds to this class throughout model range. However, recently a series of products from individual manufacturers have begun to appear that do not have defective pixels.

How many pixels are there on the matrix?
It's very easy to calculate; you just need to multiply the number of vertical lines by the number of horizontal lines.
Examples:
XGA - 1024x768 = 768,432
WXGA - 1280x800 = 1024000
SXGA - 1280x1024 = 1310000, etc.

What pixel defects are there?

The standard distinguishes 4 types of defective pixels:

Type 1: Constantly lit pixels, visible as a white dot.

Type 2: Constantly lit pixels, visible as a black dot.

Type 3: Pixels with other defects, including defects in the subpixels and RGB cells that make up the pixel. This means red, green, and blue pixels that are constantly lit or flashing. Experience shows that this is the most common defect.

Type 4 (Group of Bad Pixels): Multiple bad pixels in a 5 x 5 pixel square.

Now look at how many defective pixels are allowed for every million pixels of the matrix according to ISO 13406-2 standard:

Specific values ​​are shown in the following table:

P.S. If there are 1 million and one pixels on the matrix, the defective pixels are rounded up.
For example, for a class 2 WXGA matrix with 1,024,000 pixels, defects of type 1 - 3 pcs., type 2 - 3 pcs., type 3 - 6 pcs., clusters of type 3 - 3 pcs. are allowed.

Values ​​for all class 2 monitors.

All of the above does not mean that you will definitely get a display with dead pixels. Often, displays either contain 1-2 defective pixels or do not contain any at all.

Only if the number of defective pixels of each type on the corresponding TFT display is greater than that indicated in each corresponding cell, the product is considered defective and is subject to warranty service.

If you want to exchange an already purchased monitor with dead pixels, keep in mind that there is an international standard ISO 13406-2 regulating the permissible number defective pixels on the LCD monitor. Thus, the seller may refuse to exchange your monitor or refund your money if the number of defective pixels is .

Acceptable number of defective pixels on the monitor

The permissible number of defective pixels depends on the display class (pixel fault class). The ISO 13406-2 standard distinguishes four classes: first does not allow the presence of defective pixels. As a rule, everything is modern LCD monitors relate to second grade. Below you can calculate the acceptable number of defective pixels according to the ISO 13406-2 standard for monitors second class:

Note. In the calculation, the fractional number of defective pixels is rounded to a whole number by discarding the fractional part.

The ISO 13406-2 standard identifies the following defects: always-on white pixels (type I), always-off black pixels (type II), subpixel defects (type III), which appear as colored pixels always on/off in primary colors (red, green). , blue, cyan, magenta, yellow).

In addition, for resolutions of 1 million and higher, accumulation of color defective pixels (type III) is allowed nearby in a 5 x 5 pixel square. This defect is called a cluster. Second class monitors does not allow the presence of 5 x 5 clusters with defective pixels of type I or II. For more details see.

In practice, such a large number of defective pixels as specified in ISO 13406-2 is extremely rare. The wide tolerance can be explained by the fact that the standard was developed in 2000. Since then, LCD panel manufacturing technologies have undergone improvements.

How to check your monitor for dead pixels

Examination LCD monitor on presence of defective pixels consists of carefully examining the screen to identify abnormal pixels. The inspection is carried out sequentially for the primary colors: black, white, red, green, blue, cyan, magenta and yellow.

The question is the following - how many dead pixels are allowed in your monitors. I’m asking this because for some reason your technical support (8-800-555-55-55), the ISO-13406-2 standard and your authorized service centers cannot agree. Let’s start with the fact that in the FAQ on TFT monitors, the following is written: The permissible number of defective pixels is indicated on the last pages of the user manual. Open the last page and read: This LCD monitor meets the requirements for the number of non-working pixels ISO13406-2 Pixel fault Class IIAha, i.e. This monitor complies with Class II according to ISO13406-2 (official regulatory document), as officially stated in the instructions. We open the ISO13406-2 standard and read: Maximum number of defects per million pixels: Class____Type 1___Type 2___Type 3I________0_______0_______0II_______2_______2_______5III_______5_______15______50IV_______50______150_____500 where: Type 1 - constantly lit pixelType 2 - constantly off (extinguished pixel)Type 3 - dead subpixels (red, green, blue) So I see , that for a 19" monitor (1280 x 1024 = 1,310,720 pixels) 2 dead lights are allowed, or 2 dead ones not lit, or 5 dead subpixels (red green blue). So why then do your consultants call the number 7 and ask me what I’m not happy with it, but authorized service centers spout all sorts of nonsense - 6, 10, etc., and accuse me of taking up their time. Please explain this situation. Thank you. P.S. I didn’t find the source text of ISO 13406-2. I used the link from a search engine, supported by a dozen more similar ones, and nowhere did I find a number different from 2. If I have some outdated information, and the standard has already been changed, then please post a link to the current document.

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