Plasma TVs

Plasma TVs - a Buyers Guide

Plasma TV is the latest in display technology with excellent image quality and large screen sizes. They can be hung from a wall or freestanding. The picture quality is generally outstanding with low distortion. They need to be purchased with care as there are a wide variety of models available, some older versions suffering from noise or screen burn issues.

How Plasma TVs Work

A plasma panel sits between two thin panels of glass. It is composed of networks of pixels which are themselves tiny pockets of compressed gas. Each of these pixels contains three sub-pixels of red, green, and blue phosphor. This is the same three colour principal used in traditional cathode-ray tube (CRT) TVs. Each sub-pixel is individually controlled, allowing the Plasma panel to potentially produce over 16 million colours. When electrical current is applied to a pixel, the gas reacts to form plasma, which in turn produces light. The light then reacts with the coloured phosphors to create the picture.

Key benefits and some Things to Consider

Appearance and Mounting Options

With no tube required and a perfectly flat screen, Plasma TVs start from around 80mm / 4 inches thick. Apart from pure attractiveness, this also allows them to be wall mounted (make sure that it is a solid wall as Plasma TVs are heavy!), opening up a wider range of positioning options. As you may imagine, there is sometimes a premium to pay for ultra thin versions as the manufacturing process to achieve the miniaturisation necessary to minimise the space required by electronics comes at a price.

Aspect Ratio

This is the relationship between the screen's width and height. All Plasma TVs have a widescreen 16:9 aspect ratio. This is the correct aspect ratio for HDTV (High Definition TV), and also allows you to view many DVD movies in their original widescreen format.

Colour Accuracy

Most Plasma TVs should improve upon the colour rendering of traditional CRT units. High-end offerings are capable of displaying in excess of 16 million colours - with superb colour realism and gentle gradation between colours.

Contrast Ratio

This is the difference between the brightest of whites and the darkest of blacks. The average TV provides a contrast ratio of some 500:1, but some of the newest plasma screens have ratios of 3000:1 and 4000:1 upwards.

Display Capability and Connections

Most Plasma TVs can accept just about any video format. Typically, this will include support for composite video (NTSC, PAL SECAM) via standard RCA jacks, S-video and component video inputs, together with one or more RGB inputs for computer and gaming console video output. You need to check the specifications carefully to ensure that you have sufficient inputs for your needs. Not all Plasma TVs come with SCART connectors which may be required for equipment, such as digital satellite set-top boxes, DVD players or games consoles. There are numerous specialist switches, splitters and converters available to address any connectivity issues.

Fan Noise

Watch out for excessive fan noise in older models. Later offerings have more efficient panels which emit less heat and therefore require less cooling.

Frequency / Refresh Rate and Lower Image Flicker

The Frequency / refresh rate is the number of times a TV picture is updated each second. Most traditional TVs have a rate of 50Hz which some people may notice flickering. The latest Plasma TVs operate at 100Hz, giving a clearer picture. In addition all pixels emit light simultaneously, further reducing flicker.

Lower Image Distortion

Plasma TVs have a perfectly flat screen with no curved edges.

Magnetic Field Immunity

Unlike conventional CRT TVs, Plasma TVs don't use electron beams. They are therefore unaffected by magnetic fields. This allows them to be placed more closely to components such as home theatre loudspeakers that contain strong magnets without any image distortion. This is particularly important where space is at a premium.

Resolution

Plasma offers higher resolution than traditional TV sets and is has the potential to display full HDTV and DTV signals together with XGA, SVGA and VGA signals from a computer. As an example, you can now buy Plasma TVs with a 1024 X 1024 pixel high-resolution. Clearly, the higher the resolution, the higher the cost so you need to determine the likely use of the unit. HDTV ready units are currently carrying a cost premium (and be wary - many claiming to be HDTV ready in fact only support half of the required resolution).

Richer Sharper Images and No Scan Lines

Unlike traditional CRT screens, there is no backlight or moving electron beam - instead the image should be uniformly crisp. Most plasma TVs have built-in line doubling to further improve image quality when viewing traditional analogue video sources such as broadcasts and VCR tapes.

Sound - Nicam Stereo / Speakers

This produces reasonable quality sound from built-in speakers, usually housed at the side or at the extreme left and right of the base of the television. Some Plasma units are supplied with an external pair of speakers allowing you to either hang the unit with the speakers attached to the left and right or to remove them and mount them further apart for improved stereo effect. Many purchasers of Plasma TVs will be producing sound through a home theatre system which renders these speakers redundant.

Sound - Dolby Surround / Pro Logic

Many television programmes are now broadcast in Dolby Surround. TVs with this feature use Dolby Pro Logic to handle (decode) it. This is becoming increasingly important as Pro Logic can also be used to decode the latest Dolby Digital signals from DVD players and from digital television broadcasts.

Sound - Dolby Pro Logic II

This is an improved version of Dolby Pro Logic.

Sound - Dolby Digital 5.1

This is worth the investment if you watch a lot of DVDs or play computer games. Again, this if often handled separately via a home theatre sound system which can be separately upgraded as the technology evolves - in which case there is little benefit in paying for its inclusion in the Plasma TV unit.

Uniform Screen Brightness

Some projection televisions and home cinema projectors can suffer from uneven screen brightness. Plasma TVs illuminate all pixels evenly across the screen.

Viewing Angle

Plasma technology provides for a viewing angle of some 160 degrees both vertically a horizontally. This is a significant improvement over CRT TVs and many LCD TVs. It reproduces the image more accurately to more people in more locations throughout the room.