Understanding LCD Monitors – How to Compare LCD Monitors Based on Specifications

August 24, 2007

How to Compare LCD Monitors Based on Specifications

LCD or flat panel computer displays are the latest and greatest offerings in the desktop computer industry. They have been used for years in the portable and notebook computing markets, but recent developments have increase performance and size while reducing costs making them viable in the desktop environment. LCD displays are lightweight, extremely thin and use much less power than CRT based monitors.

Screen Size

Unlike CRT monitors, LCD displays are marketed by the actual screen dimensions. This is the measurement of the displayable area of the screen from the lower corner to the opposite upper corner of the display. One of the more confusing aspects with LCD’s is their aspect ratio of the screen. Most CRT displays have a 4:3 ratio of horizontal to vertical measurement.

Some LCD screens are marketed as a wide screen display that still have the marketed diagonal measurement, but its aspect ratio can be similar to the 16:9 displays used by wide screen TVs. So be sure to look for the aspect ratio or the vertical and horizontal measurements as well.

Native Resolutions

All LCD screens can actually display only a single given resolution referred to as the native resolution. This is the physically number of horizontal and vertical pixels that make up the LCD matrix of the display. Setting a computer display to a resolution lower than this resolution will either cause the monitor to use a reduced visible area of the screen or it will have to do extrapolation. This extrapolation attempts to blend multiple pixels together to produce a similar image to what you would see if the monitor were to display it at the given resolution but it can result in fuzzy images.

Here are some of the common native resolutions found in LCD monitors:

  • 14-15″: 1024×768 (XGA)
  • 17-19″: 1280×1024 (SXGA)
  • 20″+: 1600×1200 (UXGA)
  • 19” (Widescreen): 1440×900 (WXGA+)
  • 20” (Widescreen): 1680×1050 (WSXGA+)
  • 24” (Widescreen): 1920×1200 (WUXGA)
  • 30” (Widescreen): 2560×1600

Contrast Ratio

All LCD screens get their brightness from lighting behind the actual LCD films. This light has the tendency to wash out the colors and provide a close approximation on most colors. The contrast ratio of a LCD flat panel is the rating of how distinguishable various shades of color are. The higher the contrast ratio of the screen, the better the color representation is by the monitor. When comparing monitors try to find two models of similar size from the same manufacturer with different contrast ratios. The screen with the higher contrast ratio should have better color.

Viewing Angles

LCD’s produce their image by having a film that when a current runs through the pixel, it turns on that shade of color. The problem with the LCD film is that this color can only be accurately represented when viewed straight on. The further away from a perpendicular viewing angle, the color will tend to wash out. The LCD monitors are generally rated for their visible viewing angle for both horizontal and vertical. This is rated in degrees and is the arc of a semicircle whose center is at the perpendicular to the screen. A theoretical viewing angle of 180 degrees would mean that it is fully visible from any angle in front of the screen. A higher viewing angle is preferred over a lower angle unless you happen to want some security with your screen.

Response Times

In order to achieve the color on a pixel in an LCD panel, a current is applied to the crystals at that pixel to change the state of the crystals. Response times refer to the amount of time it takes for the crystals in the panel to move from an on to off state. A rising response time refers to the amount of time it takes to turn on the crystals and the falling time is the amount of time it takes for the crystals to move from an on to off state. Rising times tend to be very fast on LCDs, but the falling time tends to be much slower. This tends to cause a slight blurring effect on bright moving images on black backgrounds. The lower the response time, the less of a blurring effect there will be on the screen.

Connectors

Most LCD panels still use the traditional analog VGA connector known as the DSUB-15 or HD15 connector. This is the same connector that is used on all CRT monitors and on most PC video cards. Newer LCD displays and video cards are starting to use the DVI connector. This is a digital interface that is supposed to allow for a cleaner and brighter picture compared to standard VGA connectors. Check to see what type of connector your video card can use before buying a monitor to ensure you get a compatible monitor. Some monitors may also come with composite video connectors to allow them to function as a TV screen.

By Mark Kyrnin

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2 Responses to “Understanding LCD Monitors – How to Compare LCD Monitors Based on Specifications”

  1. PrerJegefab Says:

    Stunning blogpost, did not thought reading it would be so stunning when I read your title.


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