BUYER'S GUIDE TO TFT LCD SCREENS

The old bulky CRT screens have been replaced with Thin Film Transistor, Liquid Crystal Displays. LCD monitors use less then a quarter of the space taken up by a CRT monitor, and use a third of the power. LCD monitors also give a much sharper picture, and are easier on the eyes since the pixels stay continuously on or off, instead of flashing every time the screen is refreshed.

A buyer should consider the following points when shopping for an LCD monitor.

SIZE
The first and most obvious question facing the prospective LCD buyer is the question of size. Products can range from 2.5” to 50” screens. The quoted sizes for LCD screens are the actual diagonal dimensions of the picture. For in car screens the most common sizes for in dash units are 6.5” to 7”, ceiling mounts are usually 7” to 15” and headrest and stand mounts are generally 5’6” to 8” screens. LCD TV’s will vary from 15” to 32”.  

A AND B GRADE QUALITY MONITORS
Almost all the important components of the LCD monitor are in the LCD panel module, which are standard parts produced by about 6 to 8 major manufacturers. The manufacturers add a case, power supply and driving electronics. B Grade Monitors will be cheaper and some will have defects such as dead pixels, which occur when a transistor fails. The LCD panel manufacturers test the panels, grade them accordingly, and then sell them on to monitor manufacturers. This means that a very cheap monitor is likely to have a third rate or B Grade panel inside it that could even be second hand. An expensive monitor will have a new A grade panel, and is unlikely to have any defects or dead pixels. Cut-price monitors may also use older designs of LCD panel, with inferior contrast ratios, viewing angles, and response times. All NESA monitors are new A grade panels with high response rates and the widest view angles.

WIDESCREEN OPERATION
All NESA combos can be operated in widescreen, zoom or normal mode.

SLIM ATTRACTIVE DESIGN
Most customers are attracted to a slim, sleak design. Bulky units look less attractive when installed.

REFRESH RATES AND RESPONSE TIMES
A CRT monitor shows a picture by continuously redrawing the entire screen many times a second. How quickly it does this, is set by the refresh rate setting in your graphics card driver options. 60Hz corresponds to 60 refreshes a second, and at that setting you can see the flicker as the screen redraws itself which causes headaches and eye strain in a very short time. A higher refresh rate of 85Hz looks much better, but can still cause eye strain after a few hours of use. An LCD monitor is more comfortable to use all day, since each pixel of the screen is controlled by its own transistor, and stays lit up until it gets a signal to change it. Only what is changed is updated. This means there is no flicker and a sharper image, which is considerably better for your eyes.
The liquid crystal inside an LCD monitor takes a certain amount of time to change from transparent to opaque. This delay is very noticeable on older LCD monitors where ghosting can occur as the screen is updated. This delay is referred to as the response time, and is a very important specification to look up when you are shopping for an LCD screen. A lower response time is always better.

RESOLUTION
Most LCD screens have comparable resolution specifications for a particular size. For instance a 7” LCD monitor will generally have a 1440 x 234 resolution. This is actually the number of pixels wide by high.

WIDE PICTURE ANGLE
All NESA screens can be viewed from up to 150 degrees R & L. The screens have been treated with a low reflective coating and have excellent colour, contrast and clarity.

CONTRAST RATIO
Especially on TV’s this can be important in giving a sharper picture. The higher the contrast ratio the sharper the image.

TOUCHSCREEN OPERATION
Some LCD monitors are equipped with touchscreen operation. This mean that you can control the screens operation and sometimes the head unit by simply touching the screen, This is a more expensive component but sometimes a useful one.