The Plasma TV Option
Plasma technology was behind the first flat TVs we ever saw, having been originally developed specifically for video playback for the 1998 Nagano Winter Olympics.
Plasma screens are made up of rows of plasma cells, with each cell representing one pixel of picture resolution. Within each cell you get red, green and blue phosphors, a device for supplying current, and a gas that glows when fed that current. Each separate pixel is thus self-illuminating, rather than passively lit as is the case with LCD-based screens.
Plasma was once supported by almost every AV brand, but manufacturing difficulties and expenses have seen many brands defect to LCD, abandoning plasma completely.
Plasma’s main supporter is Panasonic, but Samsung and LG both make plasma TVs too, with other more niche brands including NEC and Runco.
The key pros and cons of plasma technology look like this:
Wide Viewing Angles
Because of their self-emissive nature, plasma panels are much more tolerant of wide viewing angles than LCD TVs. In fact, you can often be sat almost at right angles to a plasma TV before it loses significant contrast or colour.
Fast Response Time
Because plasma cells don’t depend on anything physically moving (liquid crystals have to open and close), they can react much more quickly to changes in image content. Panasonic quotes a response time of 0.01ms for its current mainstream plasma TVs, whereas typical LCD response times clock in at between 4ms and 8ms.
All this talk of milliseconds might not sound much on paper, but it can be the difference between moving objects retaining or losing clarity as they cross the screen.
Contrast/Black Level Response
The fact that each individual cell in a plasma screen lights itself has a very positive effect on plasma’s ability to produce dark colours, especially black. For when a plasma cell finds itself in a dark part of a picture, it can be told on an individual basis not to generate much light.
With LCD, on the other hand, the pixel array is illuminated by external light sources, making it difficult to control the light accurately on a pixel by pixel basis.
Consistent Cross-screen Light Levels
Because each pixel in a plasma display illuminates itself, you don’t have to worry about some areas of the picture looking distractingly brighter than others during dark scenes, as can happen with all LCD technologies.
The fact that each separate cell has to be charged individually has created some tricky hurdles for plasma brands to clear in keeping up with EU energy targets. So far they’ve managed it, but although some plasma makers deny this, we’ve also had sources within the plasma world suggest that plasma performance standards might be affected if the energy consumption regulations continue to be tightened.
Although this is much less of an issue than it used to be, some plasma screens still find it difficult to achieve natural, rich red and green colours. Various attempts have been made to counter this, from using elongated pixels with unequal RGB phosphor sizes to Panasonic’s recently introduced Red push technology. But rogue colour tones certainly still appear regularly on relatively cheap screens, especially when watching standard definition.
If you keep a particular, bright, colour-rich image element – like a channel logo or video game meter – in the same place on a plasma screen for too long, the phosphors 'tire' in that area, leaving behind a long-lasting, potentially permanent shadow of that bright item that’s clearly visible over other pictures.
Again, this is far less troublesome an issue than it used to be, with Panasonic in particular really getting to grips with it. But some recent plasma sets we saw from LG (the 50PK790 and 50PK990) reminded us that the problem hasn’t completely gone.
Since the image retention issue is at its worst in the early life cycle of a plasma TV, we still urge anyone who buys one to be particularly careful how they use it for the first 100 hours or so.
The difficulty with regulating the current going into plasma cells can leave images looking slightly fizzy if you sit too close to them. Also, some plasma TVs can produce gentle dithering noise over fast-moving objects – especially skin tones. Though once again, this issue is far less common than it used to be.
Lack of Brightness
Plasma TVs are generally characterised by a more muted look than LCD TVs. This can actually be a good thing in a home environment, but can certainly hurt the technology in shop 'shootouts'.