LCD screens in a nutshell (page 9: Understanding dead pixels)

Understanding dead pixels

Alarming news, manufacturers are allowed to sell us defective screens. And most of the times you can’t even complain about it. This might sound redundant, but the origin comes from the ISO norm 13406-2.

The ISO norm 13406-2 defines four different screen ranges. The highest and strictest is the class 1. This class forbids any malfunctions. This category is the best. The worse, “Class 4”, authorizes up to 549 malfunctions, and 1344 defective pixels and sub-pixels for a 20” screen. Fortunately, no manufactures refer to this class.

Almost all manufacturers base their products guaranties on Class 2.

On the top of the class category, three kind of malfunctioning have to be identified: permanent white pixels, black pixels, and color pixels (red, green, blue).

Regarding the ISO norm, here is the calculation of malfunctioning acceptance by screen size:

So in practice, a manufacturer doesn’t have to replace your 17” screen if you have two white pixels, 2 black pixels and 5 color pixels dead.

Nevertheless, some manufacturers are flexible on that area. They even change your screen if the dead pixel is located to a very irritating place (the middle of the screen by example). Ask the reseller about the possible option for dead pixels. Ideally, ask the reseller to switch on the screen in front of you.

Last possibility; buy your screen from a money-back guarantee shop. Otherwise, with on line retailer you have by law up to seven days return you product.

So one more time: This norm ISO-13406-2 should really be reviewed soon! (three time)