Industry Dead Pixel Standards

The following page sets out laptop screen industry standards with regards to dead pixels and provides background information regarding LCD screen technology.

Dead Pixels

Notebook LCDs vary in size and resolution. Resolution is defined as the number of small pixels that make up a notebook screen. The dot is the smallest unit that makes up an image.

Most notebook screens sold today are TFT active matrix notebook LCDs. TFT active matrix is a technology in which each dot has a transistor attached to it to control the backlight shining through. Each dot is made up of 3 sub-pixels (red, green and blue) with each having its own transistor. Each of these pixels turns on and off and filters light through colored sub-pixels which results in an image.
Occasionally, these individual transistors will short or remain open resulting in a bright or dark dot on the notebook screen. There are two occurrences which define a bright or dark dot: an illuminated dot, which appears as one of possibly several randomly placed white, red, blue and/or green dot elements on a dark background; or a "missing" dot, which appears as a black dot on light-colored background. Together, bright and dark pixels are also known as "dead pixels."

Failure Rate

Considering the number of pixels contained in a notebook LCD, the defective rate should dead pixels be present is usually quite minute. For a typical notebook screen, a 15.4 inch screen with WXGA resolution (1280 x 800 pixels), has a total of 1,024,000 pixels and 3,072,000 red, green and blue sub-pixels (1280 x 800 x 3). So a notebook LCD with 5 dead pixels has a defective rate equal to 0.0005%.

Why Has The Industry Established an Acceptable Level of Dead Pixels ?

To better answer this question, a comparison between a TFT active matrix LCD screen and a CRT monitor will help illustrate why the market players have established standards for LCD screens.

Dot defects can be noted in both CRT monitors and LCD screens. During the manufacturing process for both CRT monitors and LCD screens, dot outage is difficult to assess. Only upon completed assembly can an individual display be assessed for dead pixels. The more units classified as defective in a production line due to dot malfunction, the lower the overall yield. The lower the overall yield results in scrapped materials from those defective units and therefore higher production costs. With higher volume production and lower material costs as well as improved manufacturing methods for CRT monitors, if there is a decrease in yield it has a minimal effect. However, for LCD screens which have lower production yields and higher material costs based on current manufacturing methods, every attempt is made to reduce the number of scrapped displays. The higher production costs of LCD screens is the main reason this issue is more prominent with LCD screens than it has been with CRT monitors.

As a result of higher production costs of LCD screens, like their CRT counterparts, LCD screen manufacturers and notebook makers have set limits as to how many defective pixels are acceptable for a given LCD screen, based on user feedback and manufacturing cost data. The goal in setting these limits is to maintain reasonable product pricing while minimizing distraction from defective pixels for maximum user comfort. LCD screen manufacturers (i.e. AU Optronics, LG.Philips, Samsung and Sharp) and notebook makers (i.e. Apple, Dell, Fujitsu, HP Lenovo, Sony and Toshiba) have worked together to strike a balance between functionality of a screen and affordability of a notebook. The very price that a customer has paid for a notebook computer is directly related to the dead dot limits set by these industry players. The cost of accepting only perfect displays could significantly increase the price of a portable computer using an LCD screen. This is true of all notebook computers using LCD technology.

Industry Standards

There is no one clear industry standard regarding an acceptable level of dead pixels. Each notebook LCD screen manufacturer and each notebook maker have their own dead pixel standards. And unfortunately, in most cases the end-user is not aware of their respective notebook brand's dead pixel policy until after a notebook is purchased and dead pixels are noticed. LCDs4Less, however, would rather take the approach of educating our customers about industry standards and being proactive in informing our customers about our dead pixel policy.

The following table is a summary of various notebook brands' and LCD screen manufacturers' dead pixel policies. The data provided below is subject to change by the notebook manufacturers and LCD screen manufacturers and vary depending on size, resolution and brand. The amounts represent in general the number of dead pixels required for screen replacement.

^(a) HP: 6 or more pixels for XGA and WXGA resolutions, 7 or more pixels for WXGA+ and SXGA+ resolutions, 8 or more pixels for WXGA+ and UXGA resolutions and 9 or more pixels for WUXGA resolution are required for replacement. Also, for any of the resolutions above, any 2 bright pixels within 25 mm or any 2 dark pixels within 15 mm of each other are allowed for replacement.

ISO 13406-2 Standard

To regulate the accceptability of defects and to protect the end-user, ISO has created a standard for manufacturers to follow. ISO 13406-2 recommends how many defects are acceptable in an LCD screen before it should be replaced, within the terms and conditions of warranty.

ISO 13406-2 states that all reputable manufacturers should conform to and support the ISO 13406-2 standard.

Conclusion

LCDs4Less recognizes the importance of customer satisfaction and providing a quality product. In keeping with the industry, LCDs4Less.co.uk either meets or exceeds industry standards. While LCDs4Less.co.uk strives to provide the best dead pixel policy, we can not exceed those standards provided to us by the manufacturers and still provide the best prices in the industry. We continuously monitor the industry’s standards to improve our policy as manufacturing methods and production costs improve.

We have established two types of screen purchases and two types of warranty. A standard screen purchase, "Customary", allows up to 2 dead pixels and is replaced if it has 3 or more during the warranty period. To accommodate more demanding customers we have established a "Premium" screen purchase. A Premium screen purchase is shipped with 0 dead pixels, allows up to 2 dead pixels and is replaced if it has 3 or more during the warranty period. The price for a Premium screen can be seen in the table below.

The following table sets out our return policy regarding screens with dead pixels.

Return Policy for Dead Pixels

LCDs4Less has two types of warranty: "Standard" and "Extended". The Standard Warranty is included for all screen purchases and covers items such as lines, dead pixels (amount depending on Customary or Premium purchase) and premature backlight outage for up to 180 days. The Extended Warranty covers the same items for a period of 12 months. The Extended Warranty fee is based on the pricing schedule below.

	Why buy from LCDs4Less.com?
	"The screen worked out nicely, and came at a time when the need was great. Service was prompt and more than satisfactory. Thanks again!"
	Anne R  / USA / January, 2005