This month, one of our correspondents to Mailbag (page 7) draws attention to the fact that some plasma TV sets being sold on the Australian market have 852 x 480 pixels. This is fine for the American market because NTSC broadcasts have 480 visible scanning lines (out of a total of 525 lines). But it is inadequate for PAL broadcasts which have 576 visible scanning lines (out of a total of 625 scanning lines). The set has to scale the incoming video signal to suit the number of vertical pixels so inevitably, you lose vertical picture resolution. Putting it another way, the picture on such standard definition plasma sets can never be as detailed as on a good CRT set.

But the situation is actually worse. Rather than just some plasma sets being only 852 x 480 pixels, it appears that ALL standard definition wide-screen plasma sets conform to this standard. Why? Because they are all designed to suit the American market. Sure, some of them might be HD-ready, able to accept a signal from a HD set-top box via a digital HDMI cable or analog component video (with progressive scan) but they can never display HD signals with anything more than 852 x 480 resolution.

Plasma sets (HD or SD) also use a lot of power, typically between 300 and 500 watts, depending on screen size. Just check out any plasma set in your local retailer – you can feel the heat radiating from the screen and from the top of the cabinet. That may not be a problem in winter, when it just contributes to your room heating but it is a lot of heat in summer. If you are running an air-conditioner, it will have to work that much harder to get rid of the excess heat.

I also feel that any set producing that much heat must present a long-term reliability prospect. All the electronic componentry behind the screen is subject to much of that heat.

Temporary image burn-in of station logos also seems to be a problem, even on the current generation of plasma TVs. While this may not do any permanent harm, it can be extremely irritating to see a channel logo still there, maybe days afterwards you watched several hours of a sports broadcast.

One cannot deny that plasma TVs are initially very attractive when you see them on display in the stores. They are very bright and colourful and when shown with any cartoon features, they seem even brighter. Our advice? Look carefully before you leap. Consider a high-definition LCD set or even a rear projection set over any SD plasma set. If those models seem too expensive, just wait a year – they will be much cheaper then.

And don’t be conned by extreme claims for contrast ratio. A press release for a new SD plasma set that arrived while I was writing this very editorial claims a contrast ratio of 10,000:1. This is ridiculous.

Leo Simpson