Hi
With manufacturing improving, LCD panel sizes continue to get larger
all while prices keep dropping. Retailers and manufacturers throw around
a lot of numbers and terms to describe their products. So, how does one
know what all these mean? This article looks to cover the basics so one
can make an informed decision when buying an LCD monitor.
Screen Size
The screen size is the measurement of the displayable area of the
screen from the lower corner to the opposite upper corner of the
display. LCD's typically gave their actual measurements but they are now
rounding those numbers. Be sure to find the real dimensions typically
referred to as the actual screen size whenever looking at a LCD.
Aspect Ratio
The aspect ratio refers to the number of horizontal pixels to
vertical pixels in a display. Traditional displays used a 4:3 aspect
ratio. Most new monitors use either a 16:10 or 16:9 widescreen aspect
ratio. The 16:9 is the ratio typically used for HDTVs. There are even a
few ultra wide or 2:1 aspect ratio monitors on the market but they
aren't very common.
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 cause 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:
- 17" (Widescreen): 1280x800 (WXGA)
- 19" (Widescreen): 1440x900 (WXGA+)
- 21" (Widescreen): 1600x900 (WSXGA+)
- 22" (Widescreen): 1920x1080 (WUXGA)
- 24" (Widescreen): 1920x1080 (WUXGA)
- 27" (Widescreen): 2560x1440 (WQHD)
- 30" (Widescreen): 2560x1600
Panel Coatings
This is something that most people don't think about much primarily
because the market may not give them much choice. The coatings of the
display panel fall into two categories: glossy or anti-glare. The
majority of monitors for consumers use a glossy coating. This is done
because it tends to show off colors better in low light conditions. The
downside is that in brighter light it generates glare and reflections.
You can tell most monitors with glossy coatings either through the use
of glass on the outside front of the monitor or through terms such as
crystal to describe the filters. Business oriented monitors tend to come
with anti-glare coatings. These have a film over the LCD panel that
helps reduces reflections. It will slightly mute the colors but they are
much better in bright lighting conditions such as offices with overhead
flourescent lighting.
A good way to tell which type of coating will work best for your LCD
monitor is to do a small test where the computer is going to be used.
Take a small piece of glass such as a picture frame and place it where
the monitor would be with the lighting that will be used when the
computer is. If you see a lot of reflections or glare off the glass, it
is best to get an anti-glare coated screen. If you don't have the
reflections and glare, then a glossy screen will work fine.
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 it is very deceptive.
Basically a higher contrast ratio will mean that the screen will tend to
have deeper blacks and brighter whites. Look for the typical contrast
ratio which is around 1000:1 rather than dynamic numbers.
Color Gamut
Each LCD panel will vary slightly in how well they can reproduce
color. When an LCD is being used for tasks that require a high level of
color accuracy, it is important to find out what the panel's color gamut
is. This is a description that lets you know how wide a range of color
the screen can display. The larger the percentage of NTSC, the greater
level of color a monitor can display. It is somewhat complex and best
described in my article on
Color Gamuts. Most basic consumers LCDs range from 70 to 80 percent of NTSC.
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 gray to gray rating that
generates a lower time than the traditional full on to off state
response times.
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. Note that the
viewing angles still may not translate fully to a good quality image but
one that is viewable.
Connectors
Most LCD panels have an analog and a digital connector on them. The analog connector is the VGA or DSUB-15.
HDMI
is now becoming the most common digital connector thanks to its
adoption in HDTVs. DVI was previously most popular computer digital
interface.
DisplayPort
and its mini version are now becoming more popular for high end
graphics displays. Thunderbolt is Apple and Intel's new connector that
is fully compatible with the DisplayPort standards. Check to see what
type of connector your video card can use before buying a monitor to
ensure you get a compatible monitor. You still may be able to use a
monitor with a different connector than your video card by using
adapters but they can get fairly expensive. Some monitors may also come
with home theater connectors including component, composite and S-video.
Stands
Many people don't consider the stand when purchasing a monitor but it
can make a huge difference. There are typically four different types of
adjustment: height, tilt, swivel and pivot. Many less expensive
monitors only feature the tilt adjustment. Height, tilt and swivel are
generally the critical types of adjustments allowing for the greatest
flexibility when using the monitor in the most ergonmoic fashion.
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