How to buy

Sales staff often use screen resolution and contrast ratio figures to impress customers. However, LCD and plasma TVs all use digital processing software to put a picture on the screen.

Unless it’s spot-on, this process, known as ‘up-scaling’ and ‘de-interlacing’, can lead to unpleasant side effects.

Instead of being wowed by the ‘higher the better’ numbers orthodoxy, use your own DVDs, with some of the scenes suggested below, and try these simple approaches to get a better idea of the LCD or plasma TV's real picture quality .

Picture quality on LCD and plasma TVs

Check the source of the picture you're watching in the TV showroom – LCD and plasma TVs in stores often screen HD pictures. While this demonstrates how good HD can be, it's certainly not representative of the picture quality you'll get via a standard broadcast signal or DVD.

Something plugged into the HDMI socket round the rear of the LCD or plasma TV is a dead giveaway that you're being shown high-definition images.

Common problems with LCD and plasma TVs

Smearing

A ‘ghost-like’ effect, often visible on moving images. You’re unlikely to spot this on LCD and plasma TV displays showing simple colourful images – cartoons, say – so watch a football match instead.

Picture judder

Like smearing, this is more easily spotted on real life fast-moving action and panning shots. Images fail to move smoothly across the screen, instead making slight stuttering and juddering movements.

Edges

Watch out for over-enhanced edges on images, such as buildings or text. High resolution LCD and plasma TVs sometimes over-sharpen pictures, leading to jagged lines.

Reflections

Keep an eye out for screen reflectivity. LCD TVs tend to reflect the least – plasma TVs aren't quite as good. CRT screens are made of glass and tend to reflect more light than either

Washed out

LCD TV pictures often look a bit washed out. Check out a movie with very dark sequences, like The Matrix, and see how much detail you can pick out.

Colour-fade

The colour on some LCD and plasma TVs starts to fade when not viewed head on. LCD TVs and especially rear projection sets are particularly susceptible from acute angles.

Colour-banding

When watching something like a sunset on your LCD or plasma TV, instead of different shades of colour subtly blending into one another, colours appear in distinct bands.

LCD and plasma TV extras

Budget for the extras - most of the LCD and plasma TVs in the Which? test can be wall-mounted but none come supplied with the necessary brackets.

Universal wall-mounting kits can cost anything up to £300 extra but your new LCD or plasma TV's guarantee may only cover brackets bought directly from the TV manufacturer.

For more advice check our guide to buying TVs