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> LCD / CRT Comparison
About
LCD Monitors and CRT monitors - Comparison of technology and
advantages
- A comprehensive list of characteristics,
advantages and disadvantages of LCDs and CRTs |
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There is no doubt that CRT computer monitors
have a very limited mass-market lifespan. Several manufacturers have stopped manufacturing CRTs
completely, which means they are not easy to purchase, yet there are
attributes of CRTs that LCD screens have not been able to match. The LCD
is simply not a good choice in some environments based on their needs. The
characteristics your job's requirements will help determine
whether you switch to an LCD.
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Despite the decades of technological advances in
computing, the work horse of personal computing has been, until very
recently, the large, desk mounted CRT monitors. These computer monitors
managed to revolutionize computing, and allowed personal computers to become
a fact of daily life by utilizing the technology of the cathode ray tubes; a
technology first suggested for transmitting images in 1907. Yet, if
opened by professionals for examination, what you would see inside the
standard CRT monitor is basically the inner workings of a cathode ray tube
television.
CRTs produce images when the moving electron
beam inside the large cathode tube moves back and forth, firing electronic
beams at phosphor dots on the inside of the glass tube line by line. The
phosphors in your CRT are chemicals that emit red, green, or blue light when
struck by electrons. The smoothness of the image is determined by the scan
rate of the beam (screen flicker increases as the speed decreases). |
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This digital technology was first invented in
1971.Initially used in watches and calculators, its functionality was
quickly adopted and began redefining computer, medical, and industrial
electronics. In computing, LCDs have been used for years in laptops, and are
now ever present as flat panel computer screens, as well as being integrated
into new technology television screens. It took until 2003 for the volume of
these flat screens to escalate and capture half the monitor market. As of 2005,
LCD monitors exceed CRTs sales by more than 2-to-1. They are also
known as flat panels in both computer monitor and television screen design. |
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Basic CRT internals |
Sandwiched layers of an LCD
design |
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There are no cathode ray tubes in the very thin
LCD monitors. Instead, thin "sandwiches" of glass contain liquid-crystal
filled cells (red, green and blue cells ) that make up a pixel. Arrays of
TFTs (thin film transistors) provide the voltage power causing the crystals
to untwist and realign so that varying amounts of light can shine through
each, creating images. This particular sensitivity to light makes LCD
technology very useful in projection (such as LCD front projectors), where
light is focused through LCD chips
Specifically, there are five layers to the flat display: a backlight,
polarized glass sheet, colored pixel layering, coating of liquid crystal
solution that responds to signals off a wired grid of x and y coordinates,
followed by a second glass sheet. To create an image, electrical charges,
precision coordinated in various degrees and volts effect the orientation
of the liquid crystals, opening and closing them and changing the amount of
light that passes through specific colors of pixels. Liquid crystal display technology has
increased its accuracy, thanks to advances such as thin film transistors (TFTs
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also known as active-matrix technologies) that can produce sharp and more
accurate color images than earlier passive-matrix technologies. |
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Light weight; can be about 15 lbs for a
thin LCD. |
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Smaller footprint on desk leaving,
freeing up work area on the user's desk. |
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Flicker free screen. |
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More usable display area than on
comparably sized CRTs. |
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Low frequency radiation is practically
eliminated. |
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Easy adjustment, storage, and movement |
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Energy efficient, using only 1/3 to 1/2
the electricity of CRTs, and they don't generate heat. |
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Potentially less eyestrain due to
reduced screen glare. |
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Good for basic web surfing. |
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Newest TFT liquid crystal technology has
provided LCDs in competitive position with CRTs for image and color clarity. |
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OLED, a new technology (Organic
light-emitting diodes) in limited use presently in handheld personal video
players, uses little power and provides a better image than present LCD
technology; it thus holds the promise of making up for a significant
weakness in LCD image quality. |
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Plentiful mounting arm options
available, enabling these light LCDs, whether computer or TV monitor to be
ergonomically raised off the work surface. |
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Significantly lower cost compared to
CRTs, because the technology has matured. |
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Color fidelity, so essential for graphic
artists, has not been matched by LCDs. |
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Contrast ratio allows perception of true
black. Darks are darker. |
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Ability to adjust (multisync) images. |
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Good for basic web surfing as well as
uses requiring crisp, color-rich graphics and sharp text. |
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Work better at multiple resolution. |
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Displays full motion video better. |
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Give you more pixels, translating to
greater screen detail and ability to view more of a document without
scrolling. |
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Screen images viewed from side angle are
as good as when viewed straight-on (no dilution of clarity or
color.) |
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Modern versions may include a sleep-mode
for energy efficiency. |
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Many now available with flat viewing
screens for less glare, viewing convenience. |
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Strong glass screen can withstand
routine handling, and is not easily damaged by casual touch. |
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Fragile screen; may result in both
screen and backlight lamp damage if touched or handled. Thus, not
recommended in environments where it may be handled roughly. |
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Contrast ratio causes darkness to not be
displayed true. Darkest areas may be viewed as dark gray rather than
black. |
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Designed only for one optimum
resolution; can't adjust images. |
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Best view of screen is straight-on,
limiting clarity and colors of information for those viewing from an
angle. |
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The backlight is the potential weak link
and its failure can be costly. Many warranties only cover it for 1
year. |
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Radiation Emission; ELF from 60 Hz to 75
Hz and VLF from 10kHz to 30kHz. |
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Larger size takes up more desk space;
the bigger the screen, the bigger the footprint. |
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Heavy weight, 40 lbs and more. |
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Heavier size limits easy and convenient
movement. |
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Expends more energy and throws off heat. |
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Measurement differs from usable screen
area. EX: a 19" CRT provides about 18" of usable screen
area. |
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Less off-the-desk mounting options
available. |
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While most CRT monitors have in the past been designed with a curved screen,
technological innovation has led to the manufacture of CRT computer and
television glass screens that are almost completely flat. These Flat Screens
are still bulky in size and weight due to the cathode ray tube within, but
glare is all be eliminated and the overall quality of viewing is considered
better due to the screen design. To learn about the distinction between
the terminology of flat screens and flat panels, check
About flat
screen & flat panel.
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The health effects of the radiation emitted by
CRTs continues to be debated. Meanwhile, concerned users of CRTs are able to
purchase
anti-radiation/glare filters
without foregoing the use of their existing PC monitors.
These computer filters are
also available for flat
panels with a privacy option
(see photo to the right) |
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