A dead pixel policy is a manufacturer's set of rules regarding specific defects found in various types of monitors and televisions. These defects, known as dead pixels, occur when one or more of the tiniest of elements of the screen dies or becomes stuck. Such problems range in severity; dead pixels can affect the viewing of a picture or they can be practically invisible. The main consideration in comparing one dead pixel policy to another is whether or not the policy allows the devices to be returned, exchanged or repaired when this somewhat common problem occurs. Dead pixel policies also can apply to products directly off the assembly line, where they can be rejected before they even reach the consumer.
LCD displays, flat panel monitors, digital televisions, and high-definition televisions are all types of devices with viewing screens comprised of up to millions of tiny pixels. In any given picture on a screen, each of these minuscule dots will be in one specific state of color; collectively they make up the images that are shown. Each pixel changes as the picture changes, but occasionally one or more will not work at all. When this happens, it is called a dead pixel; it can best be seen as a tiny black dot against a bright background. Stuck pixels are similar to dead pixels, except that the pixel is permanently turned on in only one of its color states.
Most dead pixel policies treat dead or stuck pixels the same. In its most basic form, this kind of manufacturer's policy will only protect the consumer from defective equipment if the quantity of dead pixels on the screen exceeds a specified amount. This is often decided by the class of the display, which is defined by the overall number of pixels, along with the quality and price of the materials used to make the device.
There are four classes of flat-panel displays, I through IV; a higher class will typically result in a higher tolerance for dead pixels. A dead pixel policy for a class I monitor, for example, allows for no dead pixels at all. Conversely, a class IV screen can have many defects and still be deemed acceptable; this is largely due to the fact that a higher class device will have more pixels, making it more difficult to spot the dead ones. Manufacturers typically follow ISO standards when producing flat screen monitors, but these are also open to interpretation and can result in different quality levels between electronics makers.
Anyone purchasing a monitor will probably want their device to be completely free of defects. There is not a lot one can do, however; the only way to really test for dead pixels is to have the screen up and running and perform visual checks. A smart consumer may check ahead of time to see if dead pixels are a common problem in their desired type of monitor; he also may ask what the specific dead pixel policy is prior to purchasing a device.