All LCD televisions are also ready to accept HDTV (high definition television) and DTV (digital television) signals and would thus be quite functional a few years down the line, when these signals become more widespread. A majority of LCD screens can also be used as computer monitors because they can be hooked up to a VGA or DVI signal, though the resolutions of various screens tend to vary with different models and brands. Issues with the LCD television and emerging solutions Potential buyers who wish to replace their traditional CRT with the latest LCD need to be aware of the pros and cons of the new LCD technology and how the differences between the two technologies would alter their lifespan and viewing pleasure. The viewing angle for LCD televisions based on PVA and S-PVA LCD panels is limited to about 140 degrees, after which distortion sets in. For both light scenes and images and their darker counterparts, LCDs work better due to their high contrast ratio. The disadvantage of this technology lies in the appearance of ghosting when the image varies and moves between different dark shades. Televisions with CRT technology do not suffer from ghosting as the phosphor contained in the CRT panel is charged by the strike of a beam of electrons. Most of the light is emitted in a comparatively shorter period of time, usually less than 1 millisecond, compared to a refresh period of about 20 milliseconds. For an LCD television, each pixel emits light of a fixed intensity for a stretch of approximately 20 milliseconds in addition to the time it takes to go over to the next state (or the refresh period, which is usually between 12 and 25 milliseconds). This stretch of time, also known as the response time, can be lessened by the design of the panel, or through the use of overdriving technology, but the response time can only be cut down to the length of the refresh period. Bringing the response time to a level equal to the refresh period is usually enough to watch films and television programs, but for those who want to watch videos shot at 50 or 60 frames a second on certain LCD televisions, some ghosting issues still remain. |
