Defective pixel
A pixel error is a defective pixel, usually on an LCD screen. Pixel errors arise in LCDs usually caused by manufacturing faults. Such errors are possible but even with CRT displays, such as errors in the shadow mask. A pixel error manifests itself, for example by a constantly lit pixel or a constantly black pixel. In LCDs, individual subpixels may be affected by an error. While manufacturers and distributors usually are of the opinion that pixel errors are tolerable, consumers and ergonomists are mostly of the opinion that interfere pixel error considerably. Even if the user does not recognize the defective pixels, it may nevertheless unconsciously interfere, like reflections in a pair of glasses, which is why there antireflection coating is recommended. They therefore represent an Ergonomics Problem
Pixel fault classes
1) Not subpixel
As a " common " in the sense of ISO 13406-2 defined the manufacturer Pixel fault Class II and raise them so that the base standard. According to these regulations, for example, when a TFT display with a resolution of 1920 × 1080 pixels ( = 2.073 million pixels) four pixels remain lit, four pixels constantly be black and up to ten sub pixel defects. The standard series ISO 13406 was withdrawn in 2009 and replaced by the ISO 9241 series. After this error may in class II at most two pixels per constantly be bright or constantly black and it must not exceed ten defective sub-pixels to be found.
Software -related pixel error
Display errors in the form of constantly illuminated or dark pixels can also software side by incorrect device drivers or incorrect program code, especially in 3D games arise. Since this is not the form of hardware damage, but errors in the calculation of the screen contents ( 3D games about two adjacent textures without anti-aliasing ), can be solved by correcting the software the problem.
Thermal problems
Also, overheating of the imaging hardware (video card, etc. ), for example due to excessive overclocking or poor ventilation can cause display errors, but which then usually occur in the form of much more pronounced artifacts than just by a single defective pixels displayed.
Pixel errors in the digital camera
If the pixel error in image sensor of a digital camera, it is called in the case of always dark pixels of "dead pixels" ( engl. "dead pixel" ). If the pixel contrast, always bright, there is still not a common German name; The English term is "stuck pixel" ( literally " of stopped pixels "). An intermediate form represent pixels that have only in certain cases, usually at high ISO or long exposure time, an anomalous behavior. Are these pixels then too bright, they are called, also in the absence of a common German name, "hot pixel" ( " hot pixels "). An appropriate German term would be " over -sensitive pixels ". For the theoretically occurring that a pixel on the other hand is under -sensitive, there is no technical term. The effect on sensitive pixels can sometimes be reduced by active cooling of the image sensor.
For digital cameras Pixel errors can be "repaired" by the firmware of the camera in the best case. There the defective pixel is then simply ignored and instead calculated an average value of the neighboring pixels. Since this is actually about subpixels, namely a certain color, is, it should be noted that about a green pixel must be calculated from the neighboring green pixels, so there is no color distortion. A prerequisite for this method is that the firmware knows the defective sub-pixels, ie a corresponding list exists. Generally, this is determined during the manufacturing process of the camera and hard-coded. Due to aging and environmental factors, however, more often defects, such as arise each year one to three "hot pixel", the position of which must be added to know the firmware. Depending on the camera manufacturer and price range, this is done either automatically, manually, or not at all. By the latter " method ", manufacturers can more or less deliberately, because it is a simple software engineering process, to sell more expensive of cheaper cameras. Then step "hot pixel" or "stuck pixel" on, are located on each photo in the same place glowing dots, with red or blue spots appear twice as large due to the Bayer pattern commonly used as green. Such errors can be removed with image processing programs also subsequently.