Defective pixel

Defective pixels are pixels on a liquid crystal display (LCD) that are not performing as expected. The ISO standard ISO 13406-2 distinguishes between three different types of defective pixels, while hardware companies tend to have further distinguishing types.

Similar defects can also occur in a charge-coupled device (CCD) or CMOS image sensor in digital cameras. In these devices, defective pixels fail to sense light levels correctly, whereas defective pixels in LCDs fail to reproduce light levels correctly.

Variations

Dark dot defects

A dark dot defect is usually caused by a transistor in the transparent electrode layer that is stuck "on" for TN panels or "off" for MVA/PVA and IPS panels. In that state, the transistor places the liquid crystal material in such a way that no light ever passes through to the RGB layer of the display.

Bright dot defects

A bright dot defect is a group of three sub-pixels (one pixel) all of whose transistors are "off" for TN panels or stuck "on" for MVA/PVA panels. This allows all light to pass through to the RGB layer, creating a bright white pixel that is always on. This is commonly known as a "hot pixel".