LCD and plasma TV technologies may seem identical, but the similarities end once you look past the thin form factor and big-screen ethos. Plasma screens use a sheet of miniscule individual plasma cells that create a picture when an electrical charge is applied, whereas LCD screens substitute liquid crystal instead of plasma.
LCD screens, on the other hand, use liquid crystal compressed between two glass plates and an image is created when electricity is applied to these crystals. The basic concept is a simple one but there is as world of difference between these two display technologies — and each has its strengths and weaknesses.
How well an image is displayed on a television panel — whether it is a Blu-ray movie, HDTV broadcast or high-definition video game — is dependent on the technology and image processing within the TV screen itself. There are a range of determining factors which impact upon the quality of the image displayed on your screen.
A panel's contrast ratio — whether LCD or plasma — represents its ability to show detail in high contrast areas of the screen, in the form of minute gradations of colour and blacks or whites. For example, a panel with a low contrast ratio will struggle to show the higher or lower extremes of an image. In layman's terms, this means detail will be lost in bright areas as well as in dark scenes. In a Blu-ray movie, for example Batman Begins, the loss of detail in the many dark scenes will quickly become apparent.
Most manufacturers increase the contrast capabilities of their screens by dynamically altering backlight brightness. This allows extra detail to be shown in dark scenes and can be a life-saver for a panel with a low static contrast ratio. Some manufacturers have taken their estimations of this dynamic contrast ratio to excess, rating their screens at contrast ratios of 1000000:1 — and even higher. While these figures demonstrate the advantages of dynamic contrast ratio alteration, they don't need to be a big factor in your buying decision.
It is generally accepted that plasma televisions have better contrast ratio specifications than LCD panels, due to the fact that a plasma can completely deactivate the light source for individual segments of the screen. This means sections of the screen can be completely dark while others are displaying bright colour, unlike a traditional LCD screen which has a single backlight array that can only alter brightness levels for the entire screen.
A new technology has recently been developed for LCD televisions which uses a sheet of light-emitting diodes (or LEDs) as a backlight. These LEDs can be individually controlled in a similar manner to plasma pixels, allowing for section-specific brightness levels. Until this technology is incorporated into all LCD panels we still recommend plasma panels over LCD screens in terms of producing a superior contrast ratio and deep black levels.
A wide viewing angle is important if the television will be placed in a wide living area or will be regularily watched by multiple people simultaneously — most of us will at some time have family and friends around to watch the TV! The narrower a television's quoted viewing angle is, the smaller the range in which it produces a 'perfect' image with no loss of contrast or colour. Many manufacturers quote an unrealistically high viewing angle — close to a full 180 degrees in some instances — but the best way to test this is to test the screens in person.
In general, plasmas have the best viewing angles with their images remaining solid and colourful at wide viewing angles while LCDs suffer from colour shift and loss of brightness. This is not always the case though so it is best to compare panels directly against each other if possible.