Buying a TV: what you need to know and why you (probably) don’t need a huge screen

Choosing your next TV can be a challenge. How big should it be? Do you want the sharpest picture? The crispest sound? Which type would suit you best, especially if you’re partially sighted? And – hang on – what’s wrong with your current TV anyway?

Evolving technology has also brought a boom in jargon. You may know what HD and UHD mean, but what about OLED, LCD and HDR?

This Which? guide breaks down your choices and the jargon, so you can buy the TV that’s right for you – and not be lured by marketing into buying one you don’t need.

Screen size matters. Too small and you'll be squinting at your favourite shows. Too big and your TV will dominate the room.

If you do opt for a big screen, make sure you can sit far enough away to take it all in. That said, you can sit a little closer to a 4K TV because its higher resolution means you won’t discern any pixels (more on pixels later).

Check the distance from corner to corner, diagonally – just the screen, not the frame. If you don’t have a tape measure, the first number in the model name is its size (for example, 43 means it’s a 43-inch TV).

TV manufacturers love jargon, so you’ll need to understand the differences between OLED, QLED, LCD, 4K, HD, 8K and HDR. The differences relate mainly to resolution and screen technology.

If you’re in the market for a new TV, it should be a 4K model.

Watching in 4K means seeing everything on screen in crystal-like clarity. This is because of the number of pixels 4K uses:

·       Standard definition (SD) 4K – 704 x 576 = 405,504 pixels in total

·       Full high definition (HD) 4K – 1,920 x 1080 = 2,073,600 pixels in total

·       Ultra-high definition (UHD) 4K – 3,840 x 2,160 = 8,294,400 pixels in total.

An 8K TV is even more powerful, at 7,680 x 4,320 for a total of 33,177,600 pixels. But, for now, there isn't enough 8K content to make buying one worthwhile.

HDR stands for ‘high dynamic range’ and new 4K TVs now support it as standard.

Dynamic range refers to the distance between the brightest and darkest point the TV can manage, and HDR is designed to broaden it. Some advanced formats, such as HDR10 and Dolby Vision, can even adapt the contrast to suit each scene.

But the jury is still out as to whether all HDR formats live up to their hype, partly because some manufacturers and TVs don’t make the most of them.

The fundamental difference between OLED and LCD (and QLED, Samsung’s answer to OLED) TVs is the backlight. OLEDs don't have one, but LCD (also called LED) TVs do. 

OLED TVs and similarly high-end LCD or QLED TVs are likely to have similar features – the only difference is how they produce the picture.

The fact that OLED TVs produce their own light source has advantages for picture quality and design, including deep blacks, smooth motion and super-thin screens.

Modern TVs can often stumble on sound – thinner TVs means thinner speakers.

Some TV speakers can make dialogue in particular sound muffled, which the average soundbar won’t help.

To improve TV audio, some manufacturers use positional sound with strong stereo separation. This makes it easier for viewers to discern audio coming from left and right.

Dolby Atmos is technology that sends sound over your head for greater ‘immersion’. Most TVs support it, but the results don’t always live up to their promise.

To find out which TVs are easiest to use for people with sight problems, Which? partnered with the Royal National Institute of Blind People (RNIB) to develop an accessibility test.

The test looks at everything from how efficiently the screen reader tells you important information on different menus to whether you can choose which part of the screen gets magnified.

To find the most accessible TVs, go to the Which? guide – Best TVs for people who are blind or partially sighted. The results are free for everyone.

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Read more with Reader's Digest guide to 10 Fantastic 40-43 inch TVs for the home