LCD Buying Guide Page 2

There are a number of features you should consider when purchasing a new display. Some may not be obvious, so here's how you can avoid some common mistakes and misconceptions.

• USB hubs. Some manufacturers build hubs into their displays, and others offer them as extras for an additional cost. These hubs are little more than a convenient place to plug in USB devices and are not a particularly valuable feature. They are valuable only if you have USB devices that you can't conveniently plug into your computer. Very few monitors use the USB connection to allow access to the monitor's controlling circuitry. This would let you adjust the monitor from your keyboard instead of using the monitor's buttons.
  
   
• LCD backlight warranties. The backlight is a fluorescent lamp that transmits light through the LCD panel. In some cases, the warranty for this particular feature can be shorter than for the display as a whole. This means that you may have to buy a whole new monitor, because backlight coverage has run out. It's easier to repair or replace the backlight in some LCD monitors than in others, so if you plan to use this display for a long time, check on the backlight coverage.
  
   
• Dead pixels. This applies to LCDs only; individual liquid crystal cells may be permanently stuck on or off, creating a tiny colored dot that is always on (and often white or black). Many LCDs have flaws, and they may not be covered by the warranty. You have to expect a certain number of these pixel defects on an LCD; if manufacturers were to guarantee perfect panels, the price per display would have to be much higher. Fortunately, pixel defects are less noticeable on higher-resolution displays. If you're concerned about this, check the pixel-defect policy before you buy.
  
   
• Speakers. Some display manufacturers offer speakers as standard or optional items. The advantage is that they attach to the display and do not require additional desk space. This is usually a waste of money, because the quality of the speakers tends to be rather poor, especially when compared with standalone speakers of similar cost. If you do get a monitor with attached speakers, make sure there is a quick-mute button on the monitor panel, or at least an easily accessible volume control.
  
   
• Electromagnetic emissions. Europe has a number of stringent display-emissions standards to limit the emissions of certain types of electromagnetic radiation. Though most displays meet these standards to date, there is conflicting evidence about whether or not these emissions actually pose any health threat. If you're concerned about this, choose a smaller monitor over a larger one and an LCD over a CRT. Also, sit farther back from the display rather than closer, as emissions diminish geometrically with distance.
  
   
• SXGA aspect ratio. Almost all standard display resolutions are based on a 4:3 aspect ratio; this means that the shorter dimension is three-quarters as long as the longer dimension. This is the case for VGA (640-by-480 pixels), SVGA (800-by-600), XGA (1,024-by-768), and UXGA (1,600-by-1200). This is not the case, however, for SXGA, which is 1,280-by-1,024, or a 5:4 aspect ratio. If you have an LCD monitor with an SXGA native resolution and scale images from other resolutions to fill it, circles will appear squashed. Similarly, if you display SXGA images on a CRT designed with a 4:3 aspect ratio and adjust the image to fill the screen, circles will not be round. This is not a problem for most users, but if you're doing precision work, such as drafting or desktop publishing, this could cause problems.

CRTs vs. LCDs: Pros and Cons
 

CRTs are better than LCDs because:

• They cost less.
  
   
• They display more colors.
  
   
• They react faster and can display moving images without smearing or artifacts.
  
   
• They use emissive technology, which means that they generate their own light, so you can view images from any angle.

LCDs are better than CRTs because:

• They are smaller and lighter.
  
   
• They consume less energy.
  
   
• The image is crisper because each pixel is displayed by a specific set of liquid crystal cells.
  
   
• Eyestrain and fatigue are reduced because there is no flicker.
  
   
• While there is no conclusive evidence about the health hazards of low-frequency electromagnetic emissions, LCDs emit much fewer than CRTs.
  
   
• Some LCDs pivot, so you can work in landscape or portrait mode.
  
   
• LCDs are less prone to interference from other devices, and you can put two side-by-side without encountering problems.
  
   
• The image geometry is always perfect.
  
   
• The flat face of an LCD tends to reflect less glare than most CRTs.

Top Ten Buying Tips

1. Go for bigger rather than smaller when it comes to a display, if your budget and space constraints permit.
   
    
2. Digital interfaces provide better LCD images, but the measured improvement is minor for many monitors. So unless your graphics adapter has a digital connection, an analog connection will probably be good enough.
   
    
3. Check the warranty. Most manufacturers offer three-year coverage, so don't settle for less.
   
    
4. Make sure you can return the display easily if it's flawed. There can be a lot of variation among individual units of the same model, so you may be surprised when you open the box.
   
    
5. If you're buying an LCD, find out about the exchange/return policy terms regarding pixel defects.
   
    
6. The only thing likely to wear out on an LCD is the backlight; investigate if and how it can be replaced.
   
    
7. Look for easy-to-reach front panel controls that are clearly labeled and for an easy-to-use on-screen menu.
   
    
8. If you're buying a CRT, make sure that the dot or stripe pitch is sufficient to accurately display the resolution you intend to use.
   
    
9. If you're buying an LCD, make sure its native resolution is the resolution you want to use; the image will not look as good at other resolutions.
   
    
10. Both CRTs and LCDs are very reliable; you probably won't need to spend the extra money on an extended warranty.

The ABCs of Displays

Analog signal A signal that conveys the intensity of each color for a given pixel via variations in voltage.

Aperture grille A set of vertical metal bars that directs the electron beam in a CRT so that it strikes only the phosphors of a desired color.

Cathode-ray tube (CRT) A vacuum tube technology used in some computer displays as well as televisions.

Digital signal A signal that uses a sequential stream of binary data-on and off signals-to convey the intensity of each color for a given pixel.

Dot pitch The distance on a CRT between the center of a phosphor dot of a given color and the center of the next nearest dot of the same color.

Liquid crystal display (LCD) A constant display that uses thin layers of special materials to block or transmit light to create an image.

Phosphor A chemical compound that emits light when excited by electrons. Different formulations produce lights of different colors.

Shadow mask A sheet of metal with round holes across its surface, used to direct the electron beam in a CRT so that it strikes only the phosphors of a desired color.

Stripe mask A metal grille that directs the electron beam in a CRT so that it strikes only the phosphors of a desired color.

Stripe pitch The distance on a CRT from the center of a phosphor stripe of a given color to the center of the next stripe of the same color.