Guide to LCD Monitors
Posted: Wed Jul 30, 2008 6:28 pm
Guide
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. Many 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 physical 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": 1024x768 (XGA)
17-19": 1280x1024 (SXGA)
20"+: 1600x1200 (UXGA)
17" (Widescreen): 1280x800 (WXGA)
19" (Widescreen): 1440x900 (WXGA+)
20" (Widescreen): 1680x1050 (WSXGA+)
24" (Widescreen): 1920x1200 (WUXGA)
30" (Widescreen): 2560x1600
Contrast Ratio
Contrast ratios are a big marketing tool by the manufacturers and one that is not easy for consumers to grasp. Essentially, this is the measurement of the difference in brightness from the darkest to brightest portion on the screen. The problem is that this measurement will vary throughout the screen. This is due to the slight variations in the lighting behind the panel. Manufacturers will use the highest contrast ratio they can find on a screen, so its somewhat deceptive. Basically a higher contrast ratio will mean that the screen will tend to have deeper blacks and brighter whites.
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. Most response times now refer to a grey to grey rating that doesn't do the full on off state that generates a lower time than the traditional reponse times.
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. HDMI and DisplayPort are two other digital interfaces that are becoming common. 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 home theater connectors including component, composite, S-video and HDMI for use with TV or DVD sources.
LCDs
Pros:
Smaller and Lighter
Energy Efficient
Causes Less Eye Fatigue
Cons:
Blurry Images Outside Native Resolution
Motion Blur on Fast Moving Images
Some Models Have Reduced Color Clarity
CRTs
Pros:
Multisync Capable
High Refresh Rates
Color Clarity and Depth
Cons:
Very Heavy and Large
Use Large Amounts of Energy
Generate Excess Heat
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. Many 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 physical 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": 1024x768 (XGA)
17-19": 1280x1024 (SXGA)
20"+: 1600x1200 (UXGA)
17" (Widescreen): 1280x800 (WXGA)
19" (Widescreen): 1440x900 (WXGA+)
20" (Widescreen): 1680x1050 (WSXGA+)
24" (Widescreen): 1920x1200 (WUXGA)
30" (Widescreen): 2560x1600
Contrast Ratio
Contrast ratios are a big marketing tool by the manufacturers and one that is not easy for consumers to grasp. Essentially, this is the measurement of the difference in brightness from the darkest to brightest portion on the screen. The problem is that this measurement will vary throughout the screen. This is due to the slight variations in the lighting behind the panel. Manufacturers will use the highest contrast ratio they can find on a screen, so its somewhat deceptive. Basically a higher contrast ratio will mean that the screen will tend to have deeper blacks and brighter whites.
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. Most response times now refer to a grey to grey rating that doesn't do the full on off state that generates a lower time than the traditional reponse times.
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. HDMI and DisplayPort are two other digital interfaces that are becoming common. 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 home theater connectors including component, composite, S-video and HDMI for use with TV or DVD sources.
LCDs
Pros:
Smaller and Lighter
Energy Efficient
Causes Less Eye Fatigue
Cons:
Blurry Images Outside Native Resolution
Motion Blur on Fast Moving Images
Some Models Have Reduced Color Clarity
CRTs
Pros:
Multisync Capable
High Refresh Rates
Color Clarity and Depth
Cons:
Very Heavy and Large
Use Large Amounts of Energy
Generate Excess Heat