The question is why choose LCD over CRT? There are several pros
and cons to consider, and the few items listed below will be
considered in this Geek Tip.
Price
The price of LCD monitors is much lower
than a few years (or even months) ago, but still far exceeds the
price of a comparable CRT monitor. For example, I spent about $600
(US) on a Viewsonic VA-720 17" LCD monitor in early 2003, and see
that the same model now sells for less than $300. A significant
price drop, but in comparison a 17" Viewsonic CRT monitor can
currently be purchased for less than $100. The ratio of prices may
have narrowed from about 5:1 to 3:1, but the aging technology behind
CRTs still allows it to hold the lead.
You can't even compare prices of CRTs to LCDs in
CompGeeks monitor section as they are right in step with the sales
information provided above, and now only carry LCD monitors. Prices
vary, even among LCD monitors of the same screen size, so there has
to be something more to it than price.
Size
One reason that LCDs have gained in
popularity is because of their small foot print. The overall size
and weight of CRT monitors far exceeds that of LCD monitors. CRTs
share the same image processing technology with tube televisions,
and therefore share the same bulky style of housing. For example,
the manufacturer's web page lists this ACER 19" LCD monitor as
having a depth of a mere 6.9" (including the base) and a weight of
12.1 pounds. As a point of reference, a 19" ACER CRT is
significantly larger with a depth of 16.86" and a hefty weight of
46.31 pounds.
Desktop real estate is precious, and an LCD will
require only a small fraction of the depth that a CRT would
require. And if there isn't even enough room on your desk for a
slim LCD monitor, the low weight makes them perfectly adaptable to
be hung on the wall, or off of a radial arm mount, such as this one
from Office Innovations.
Image
Quality
Image quality is generally considered to
be better on an LCD, as each pixel is generated by a specific set of
transistors in the screen, which produces a crisp image. But some
features that fall under the general heading of image quality might
not favor an LCD, including viewing angle, brightness, and contrast.
Early LCD monitors had a fairly narrow viewing
angle that made clearly seeing the screen from anywhere but directly
in front of it difficult. This has improved greatly, but still
doesn't quite rival the viewing angle of CRTs which provide the same
picture quality regardless of the angle. A monitor with a maximum
vertical viewing angle of 120 degrees should not be hard to find at
this point, with many monitors now being able to provide an even
greater angle.
Brightness is an area that LCD monitors may have
the edge over CRTs, but it varies widely from unit to unit. The
standard measure for brightness is referred to as "nits", which have
units of cd/m2 (candelas per square meter), where a higher number is
better. Looking at the three 17" LCD monitors currently available
as examples shows two with brightness specifications of 400 cd/m2
and one with a brightness specification of 250 cd/m2. As a
comparison, the typical CRT monitor may provide half the brightness
of an LCD, as confirmed at Viewsonic's Monitor University.
Contrast is similar to brightness in the fact
that it varies widely from unit to unit, and is a specification
where a higher number is desired. The contrast is represented as a
ratio, where higher numbers imply that bright colors can be
displayed next to dark colors without them appearing washed out.
Monitors with lower numbers in the ratio may also result in dark
shades being displayed as just black, and any detail in these areas
may be lost. As a point of reference, CRT monitors may have
contrast ratios around 700:1, and using the three 17" LCD monitors
currently available as examples shows two with contrast ratios of
450:1 and one with a contrast ratio of 400:1. 400:1 and 450:1 are
quite respectable values for LCD monitors, but CRTs may still have
the edge in this department.
Energy Consumption
LCD monitors definitely hold the edge
over CRT monitors when it comes to being energy efficient. The huge
tube in a CRT monitor is the source of most of its energy
consumption, and a comparably sized LCD may use just a fraction of
the electricity. Taking a look at this 19" Jetway LCD monitor shows
that it consumes 48 Watts during normal operation, which is less
than your typical light bulb. In contrast, a 19" CRT such as this
one from Viewsonic may draw up to 160 Watts. Therefore the fraction
of electricity used in this case is 3/10, and could translate to
noticeable savings on your electric bill.
Personal Health and Comfort
The
main benefit that LCDs have when it comes to comfort is the reduced
strain on your eyes. The reduced glare on the screen's surface, and
the elimination of a typical CRT's "refresh", can prevent your eyes
from getting tired from extended use. A CRT monitor redraws the
image on the entire screen as it refreshes, whereas an LCD monitor
only changes the necessary pixels during a refresh.
There may also be the unquantifiable effect of
reduced electromagnetic emissions on LCD monitors. The exact impact
of electromagnetic emissions may not be fully understood, but in
general less is considered to better, as addressed in this article.
And, your back may also appreciate an LCD when it comes time to
move, as the example above shows a 19" LCD monitor weighs about ¼ as
much as its CRT counterpart.
Response Time
The transistors that create the image on
a TFT LCD can be a bottleneck to its performance, especially in fast
paced 3D games where speed is critical. Related to the different
approach taken with screen refreshes, the amount of time it takes
the pixels to change in order to display the new image is referred
to as the response time. If the response time is too slow, one may
experience blurred images or ghost effects where the previous image
is still slightly visible with the new image.
LCD monitor response times have greatly improved over the past few
years, and many LCDs are now fast enough to consider for serious 3D
gaming use, but specifications still vary from unit to unit. A few
years ago a typical response time on an LCD monitor may have been
anywhere from 30 to 50 milliseconds, and today these numbers can get
down into the single digits, with anything 25 milliseconds or less
being quite common (lower is definitely better). Using the three
17" LCD monitors currently available as examples shows two with
response times of 25ms and one with a response time of 16ms.
Final Words
In addition to some of the positives
mentioned, many LCD monitors now incorporate other features to make
them more practical and even fun. LCD monitors can now be found
with integrated USB hubs, stereo speakers, and TV tuners (such as
this 15" Sharp unit), and for the right price HDTV is even an
option.
LCD monitors will continue to replace CRTs as
they become less expensive and the many benefits are realized by
consumers, but CRTs won't disappear all together as many situations
require the performance that LCDs currently can't provide.
