Flat Panel TV/Monitor Information and Cautions
Differences between LCD and Plasma sets:
1) Weight. Plasma sets size for size are considerably heavier than LCD.
2) Power. Plasma sets consume much larger amounts of electrical current than LCD.
3) Heat. Plasma sets tend to generate large amounts of heat, considerably more than LCD sets.
4) Repair Expense. Plasma sets tend to be more expensive to repair due to their added complexity over LCD.
5) View Angle. Most plasma sets tend to be more viewable from the sides than LCD, although recent technology has allowed
higher end LCD models to have very wide viewing angles. ( Sony Bravia LCD's have a 178 degree viewing angle.)
6) Display Speed. Plasma sets have a very fast display that uses phosphor dots similar to a regular direct view set to create
light which produces a rich fast moving picture. LCD displays count on an LCD matrix to block the backlight behind it. To
go from light to dark the LCD matrix has to be biased by voltage which causes it to physically twist and allow light thru.
The time it takes to twist and untwist is called latency and on cheaper models can be problematic if the latency period is
too long. When shopping for LCD sets watch for brief trailing or blurring behind fast moving objects. If you see this
characteristic it is likely that you will not be happy with the product. Most higher end LCD sets will not display this problem.
7) Contrast Ratio. The major advantage of plasma over LCD early on used to be the contrast ratio, however the later model
higher end LCD sets now equal and sometimes exceed that of plasma. To understand contrast ratio, consider that in
order to achieve a perfect picture you need a display that can range over a scale of extremely white whites on one end of
the scale and plunge the picture all the way down to extremely black blacks at the other end of the scale. When I say
black I don't mean charcoal grey I mean the total absence of light. This is where LCD displays originally had their shortfall.
The light creating the picture on LCD panels is created by fluorescent lamp strips located behind the display and is called
the backlight. The LCD panels job which is in front of the light source is to act as a valve for the light at very specific points
on the screen. At times, the LCD valve should open and let light through (whites) or should completely close off all light
leaving that point black. The question becomes, when black is required can the LCD panel completely shut off all of the
backlight ? The answer on many cheaper brands and earlier models is no it probably can't completely. If you view a black
screen in a dark room will it appear black or will it glow in the dark. This quality is a consideration if you are looking for
optimum viewing quality. Most higher end quality LCD sets now will have contrast ratio's that are 20,000:1 or higher
and this is something you should look for if purchasing an LCD just remember that manufacturers can play with this
number and what you really want is black blacks not grey blacks. The higher the number the better. Even plasma sets
should have this item taken into consideration even though they don't have a backlight to deal with. Plasma sets will pulse
phosphor dots to create brightness and darkness. The faster it pulses the phosphor the brighter the picture. When
darkness is required the pulses will fall back to a preset "idle" condition which will still create a certain amount of light and
this will determine how dark the picture will ever get. To decide if this is acceptable try to view a dark screen in as dark a
condition as you can and see if you can see a glow in the screen.
8) Screen Burn In. Screen burn in occurs when images or objects stay in the same place on the face of a display for lengthy
periods of time causing a permanent ghost image of the object to remain even after the set is off. This is caused by uneven
wear on the elements of the display and is usually permanent. Every attempt should be made to prevent lengthy periods of
watching sources that have objects that stay in the same place all the time. Examples of this would be leaving a set on a
channel that has banners, timers, toll free numbers or call signs at the bottom, top or sides of the screen that stay in the
same place all of the time or video games with stationary scores, readouts or unchanging scenery. Another source of
irregular screen wear is watching a wide screen set in the 4:3 mode all of the time instead of using the full screen. Plasma
sets use phosphor dots just like the older type direct view tube sets so they are just as prone to screen burn in as the older
type sets, perhaps even more so. It is not uncommon to see temporary burn in on a plasma that will eventually go away as
the rest of the cells get equal wear. It is even possible to erase some minor plasma burn in by running an all white signal on
the display for a short period of time so that all of the cells get saturated equally. It has been stated by many sources that
LCD sets are immune to screen burn in but having worked on a number of sets that came out of restaurants and businesses
where the set is always on the same channel I can tell you that this is not true. Leaving a display set on the same source with
objects like stock tickers, clocks or banners will eventually leave a permanent burn in on the display.
9) Extended Warranties. Most all of the new sets whether projection or flat panel often require board replacement to complete
repairs. Some of these boards can be very expensive. We therefore recommend that a service contract be purchased from a
reputable company to cover potential repair costs.
1) Weight. Plasma sets size for size are considerably heavier than LCD.
2) Power. Plasma sets consume much larger amounts of electrical current than LCD.
3) Heat. Plasma sets tend to generate large amounts of heat, considerably more than LCD sets.
4) Repair Expense. Plasma sets tend to be more expensive to repair due to their added complexity over LCD.
5) View Angle. Most plasma sets tend to be more viewable from the sides than LCD, although recent technology has allowed
higher end LCD models to have very wide viewing angles. ( Sony Bravia LCD's have a 178 degree viewing angle.)
6) Display Speed. Plasma sets have a very fast display that uses phosphor dots similar to a regular direct view set to create
light which produces a rich fast moving picture. LCD displays count on an LCD matrix to block the backlight behind it. To
go from light to dark the LCD matrix has to be biased by voltage which causes it to physically twist and allow light thru.
The time it takes to twist and untwist is called latency and on cheaper models can be problematic if the latency period is
too long. When shopping for LCD sets watch for brief trailing or blurring behind fast moving objects. If you see this
characteristic it is likely that you will not be happy with the product. Most higher end LCD sets will not display this problem.
7) Contrast Ratio. The major advantage of plasma over LCD early on used to be the contrast ratio, however the later model
higher end LCD sets now equal and sometimes exceed that of plasma. To understand contrast ratio, consider that in
order to achieve a perfect picture you need a display that can range over a scale of extremely white whites on one end of
the scale and plunge the picture all the way down to extremely black blacks at the other end of the scale. When I say
black I don't mean charcoal grey I mean the total absence of light. This is where LCD displays originally had their shortfall.
The light creating the picture on LCD panels is created by fluorescent lamp strips located behind the display and is called
the backlight. The LCD panels job which is in front of the light source is to act as a valve for the light at very specific points
on the screen. At times, the LCD valve should open and let light through (whites) or should completely close off all light
leaving that point black. The question becomes, when black is required can the LCD panel completely shut off all of the
backlight ? The answer on many cheaper brands and earlier models is no it probably can't completely. If you view a black
screen in a dark room will it appear black or will it glow in the dark. This quality is a consideration if you are looking for
optimum viewing quality. Most higher end quality LCD sets now will have contrast ratio's that are 20,000:1 or higher
and this is something you should look for if purchasing an LCD just remember that manufacturers can play with this
number and what you really want is black blacks not grey blacks. The higher the number the better. Even plasma sets
should have this item taken into consideration even though they don't have a backlight to deal with. Plasma sets will pulse
phosphor dots to create brightness and darkness. The faster it pulses the phosphor the brighter the picture. When
darkness is required the pulses will fall back to a preset "idle" condition which will still create a certain amount of light and
this will determine how dark the picture will ever get. To decide if this is acceptable try to view a dark screen in as dark a
condition as you can and see if you can see a glow in the screen.
8) Screen Burn In. Screen burn in occurs when images or objects stay in the same place on the face of a display for lengthy
periods of time causing a permanent ghost image of the object to remain even after the set is off. This is caused by uneven
wear on the elements of the display and is usually permanent. Every attempt should be made to prevent lengthy periods of
watching sources that have objects that stay in the same place all the time. Examples of this would be leaving a set on a
channel that has banners, timers, toll free numbers or call signs at the bottom, top or sides of the screen that stay in the
same place all of the time or video games with stationary scores, readouts or unchanging scenery. Another source of
irregular screen wear is watching a wide screen set in the 4:3 mode all of the time instead of using the full screen. Plasma
sets use phosphor dots just like the older type direct view tube sets so they are just as prone to screen burn in as the older
type sets, perhaps even more so. It is not uncommon to see temporary burn in on a plasma that will eventually go away as
the rest of the cells get equal wear. It is even possible to erase some minor plasma burn in by running an all white signal on
the display for a short period of time so that all of the cells get saturated equally. It has been stated by many sources that
LCD sets are immune to screen burn in but having worked on a number of sets that came out of restaurants and businesses
where the set is always on the same channel I can tell you that this is not true. Leaving a display set on the same source with
objects like stock tickers, clocks or banners will eventually leave a permanent burn in on the display.
9) Extended Warranties. Most all of the new sets whether projection or flat panel often require board replacement to complete
repairs. Some of these boards can be very expensive. We therefore recommend that a service contract be purchased from a
reputable company to cover potential repair costs.
If you own a flat panel LCD or plasma TV or monitor or are considering buying one you should be aware of this: