Dead pixel
From Wikipedia, the free encyclopedia
A dead pixel is a defective pixel that remains unlit on an LCD screen or a CCD or CMOS sensor in a digital camera. The term "dead pixel" is often applied to other defective pixels, but there are also separate terms. A permanently lit (white) pixel is called a hot pixel, and a pixel that stays on a solid color (red, green, or blue) is known as a stuck pixel.
In LCD manufacture, it is common for a display to be manufactured that has a number of sub-pixel defects (each pixel is composed of three primary-colored sub-pixels). The number of faulty pixels tolerated before a screen is rejected is dependent on the "class" which the manufacturer has given the display (although officially described by the ISO 13406-2 standard, not all manufacturers interpret this the same way, or follow it at all). Some manufacturers have a zero-tolerance policy with regard to LCD screens, rejecting all units found to have any number of sub-pixel or pixel defects, meaning the display is a "Class I" display. Others reject them according to the number of total defects, or the number of defects in a given group, or other definitions. Some screens come with a leaflet stating how many dead pixels they are allowed to have before you can send them back to the manufacturer. Dead pixels can also occur in clusters; these are particularly annoying, and in most cases these can be sent back to the manufacturer.
In some cases, the manufacturer sends all screens to sale, and then replaces the screen if the customer reports the unit as faulty and the dead pixels meet their minimum requirements for return.
The majority of dead pixels are only noticeable on a solid color background, for example through the use of the "Dead Pixel Checkers" which consist of 4 or 5 solid-color images.
[edit] Manufacturers which offer a Zero-Dead-Pixel Warranty
- Phillips (might only include pixels stuck in a bright state)
- ViewEra (certain models. Covers any defective pixel within 6 months of purchase)
- Toshiba (only high-end notebook models)
- Sony (VAIO entire line)
As of 2006, most LCD manufacturers do NOT offer such a warranty, and may refuse to fix or replace a monitor with dead pixels (e.g. multiple red pixels), sometimes even if the monitor arrives with the defect. Customers should exercise scrutiny and search for a manufacturer's "pixel policy".
