NW Doc

The LCD Screen

If you can read this article, you're viewing it on a screen. You can see it right? Of course you can, but do you know what resolution, refresh rate, and aspect ratio you are reading it on? Are you reading it on a laptop? What type of screen do you have? Is it transflective, or transmissive? Or maybe a touch screen or tablet? What about the contrast and how good is your viewing angle? Maybe you don't care about those things and you think your laptops screen looks wonderful. That's perfectly fine -but for those who do care, or want to consider these things when purchasing a laptop, you should read on, because not every screen that comes with a laptop is the same. In fact, they vary immensely. And for some - they make or break deal on a laptop is how the screen looks, or is able to show.

First, we need to discuss what an LCD screen is. The commonly used acronym LCD stands for liquid crystal display, in which there are two sheets of polarized material with a liquid crystal solution between them. This solution is very sensitive to electricity, and, in fact, when an electric current is passed through the liquid, is causes the crystals to group together' so that light can't pass through them. Each crystal, therefore, is like a shutter; either allowing light to pass through or be shut out, subsequently creating the pixels (dots) on your screen. So when you turn on your laptop, there is a device that connects from the main board to the screen that is telling that material in every little dot when or when not to turn on and off - and which color is being portrayed. Pretty intense huh?

So now that we know what LCD's are, what type do you have in your laptop? Yes, there are different types of LCD's; in fact - there are 3 types that are commonly utilized: transmissive, transflective, and reflective. Don't worry, they aren't that hard to describe or distinguish the differences, despite their names.

Type of LCDs

The vast majority of current notebooks feature transmissive, color, active-matrix LCDs. That's because transmissive screens offer the best-quality images and are the most affordable option for manufacturers. Active Matrix is also known as TFT, or thin film transistor. Laying diodes, or small semiconductors, over a grid of ultra-small wires, creates Active Matrix screens. When an electric current passes through the diodes, they light up in different colors, depending on the strength of the current. Thousands of these diodes next to each other form an image on the screen.

To keep the diodes in an on' or off' state, active-matrix displays use transistors, which are not found in the lower-quality passive-matrix displays. The transistors help make the active-matrix displays brighter and give them more contrast than passive-matrix displays. But what does this mean for you? Transmissive LCD's are illuminated by fluorescent backlighting and are capable of rendering the greatest color depth, sharpest text, and highest resolutions. However backlighting is a major drag on a notebook's battery and it's easily overpowered by bright sunlight. Newer technology overcomes the power issue by using low power LED lighting, like in the new Sony VAIO TX notebook. These work in the same manner of backlighting the screen, only instead of a fluorescent tube, they use several low power, high efficiency LED's (Light Emitting Diode) to supply the light. There is however, another form of active matrix technology that isn't employed as much. It is called passive matrix technology. This technology is more commonly used in stand-alone monitors or older notebooks. However, there have been improvements with passive matrix displays using new CSTN and DSTN technologies. What is CSTN and DSTN?

CSTN stands for: color super-twist nematic, an LCD technology developed by Sharp Electronics Corporation. Unlike TFT, CSTN is based on a passive matrix, which is less expensive to produce. The original CSTN displays developed in the early 90's suffered from slow response times and ghosting. Recent advances in the technology, however, have made CSTN a viable alternative to active-matrix displays. New CSTN displays offer 100ms response times, a 140-degree viewing angle, and high-quality color rivaling TFT displays - all at about half the cost.

DSTN: Short for double-layer supertwist nematic, a passive-matrix LCD technology that uses two display layers to counteract the color shifting that occurs with conventional super twist displays. It has greater color accuracy than CSTN, but is more expensive to produce. A newer passive-matrix technology called High-Performance Addressing (HPA) offers even better response times and contrast than CSTN.

Response Time

But what is response time and what do viewing angles have anything to do with my laptop screen? Well - response time is important to observe when viewing movement on a laptop LCD screen. Response time is a measurement of how fast an LCD screen can change individual pixel colors, measured in milliseconds. The larger the number, the slower the response; lower the number, the better the response. Response time plays a large role when watching movies or playing games. Have you ever noticed that on some laptops there is a ghost' or trail' when a fast scene occurs in a movie, or when you move your mouse really fast? This is largely due to the response capabilities of the display. It is important to know the capabilities of your laptop's LCD as it relates to the requirements of your application. The most common response times are 8ms (milliseconds), 12ms, 16ms, and 25ms. 8ms is an excellent response time, while 12 and 16 are average and won't cause any noticeable ghosting or trailing on LCDs. 25ms response time is considered the low end when displaying fast motion often found in today's games and movies, and this is often the point where ghosting' will be most apparent.

Widescreen or Not?

After reading that list, you might be thinking, But my laptop has a W in front of those abbreviations! What does that mean?' Don't worry! Lately, manufacturers have realized the benefits of what is known as widescreen' aspect ratio screens. Widescreen is, just as it sounds, wider than a normal screen, meaning its width is more than it's height (comparably 1.6 times wider than it is higher (16:10), as compared to normal aspect ratios of 4:3.)

4:3 or standard screen

The real advantage of notebooks with a widescreen display - which is not immediately obvious at first - is that they make widescreen formats with ratios of 1.6 to 1 to correspond better with users' natural field of view. DVD movies, for example, can be played on displays with an aspect ratio of 1.6:1 without much of an irritating black strip going across the upper and lower sections of the screen. Movies are produced in formats with aspect ratios of 1.85:1 (widescreen) or 2.35:1 (CinemaScope). Since the display area is wider, however, users get to see more of the movie using a widescreen 15.4-inch device than with a 4:3 display of the same size.

In everyday usage, you soon learn to appreciate the benefits of display width when working with spreadsheets and text documents. When working with spreadsheets, for example, you can view more cells at once, and it's just a lot easier to get two windows to fit next to each other. Individuals who work a lot with graphics will quickly see the utility in having a wider display screen, as toolbars no longer constantly get in the way of graphics and windows, but rather can be "parked" over to the left or right of the screen.

Half Life 2 in widescreen

Here are the resolutions that are associated with widescreen' aspect ratios.

Abbreviation / Resolution /Aspect Ratio
WXGA/ 1280x768
WXGA/ 1280x800 (16:10)
WXGA+/ 1440x900 (16:10)
WSXGA+/ 1680x1050 (16:10)
WUXGA/ 1920x1200 (16:10)