Here's what to consider when buying an LCD, LED or plasma television.

Resolution

Confused by the numbers? It's not too complicated once you know what they mean. The numbers refer to pixels, so 1920x1080 means a screen 1920 pixels wide and 1080 pixels high — the higher the number, the better the resolution.

As screen sizes are standardised, so too are resolutions. They’re often abbreviated to only the vertical number: for example, 1920x1080 becomes 1080.

The letters that follow the numbers are p and i. The p stands for progressive and i for interlaced. These are the types of scanning used to refresh the picture on the screen. Progressive scanning is usually better, because interlaced can create a flickering effect at lower refresh rates.

The norm’s now 1080p. However, a new crop of TVs is coming out with 4K or UHD resolution. These are roughly double the resolution of 1080p — and the detail they can display is amazing. At the moment these TVs are expensive but the price will soon drop.

User test: To do your own "user test" take a favourite DVD (or 2) to the shop to check the picture. Try to watch a "talking head" so you can check skin tones and the quality of finer details such as hair texture. Also check out a nature scene, for any bias toward red or green colours. Be wary if you have to set a control to maximum to get the best picture.

Check action scenes — can the set keep up with fast movement?

Refresh rate

If you're a sports fan, a TV with a fast refresh rate might be for you.
If you're a sports fan, a TV with a fast refresh rate might be for you.

Do you like watching sports or anything else with fast-paced action, such as playing video games? A TV with a fast refresh rate might be for you.

The rate’s usually described in hertz (Hz) and it shows how many times per second the image on the screen changes. So a 200Hz rate shows you 200 images per second.

The faster the refresh rate the sharper the images, even if the action on screen is moving quickly. However, while it’s great for sport, a faster refresh rate can make movies and TV shows feel too "flat" and "crisp" because motion blur is removed. (The standard rate for film in a theatre is 24 frames per second which would be roughly the equivalent of 24Hz.)

Size

When comparing your options, make sure you're clear on how big you need the TV to be – you don't want to be squinting at a screen that's too small or not seeing the full picture on a screen that's too big.

A useful rule of thumb is for the screen to measure a third of the distance from where you’ll sit to watch it. If your couch is 3.5m from the TV, then the best screen size is 46 inches (116cm). With the newer screens and higher resolutions you can go one or two sizes bigger if you want to, and the experience should still be good.

Also note that TVs in stores look smaller than they will in your living room. You may bring home your new 50" TV that seemed reasonable in the shop only to find it's far too large for your house.

LCD and plasma screens are promoted using quaint old-fashioned inches. If you want to do your own conversion, multiply the inches by 2.54 to get the centimetres. Or use our table (below).

Size
Inches 15 17 20 22 23 26 27 32 37 42 43 50
cm 38 43 51 56 58 66 69 81 94 107 109 127

Viewing angle

On LCD sets check how the picture looks if you step to the side or move up and down. Viewing angles have improved, but some models still have a dimmer picture when not viewed centrally – important if several people are watching at once.

Curved screens

Not all manufacturers are going down this route, but those that do are touting their benefits. But is a curved screen useful or just a gimmick?

The curve itself is based on a radius of roughly 4200mm (so if you have enough TVs you could make a 26m circle). There’s no disadvantage if you’re sitting to one side, but if you’re sitting directly in front of the TV, the display feels more immersive, which is particularly good for video games and epic movies.

The downside is curved screens reflect light sources and when they do, the reflections “streak” across the screen. So if there is any bright light behind you, it becomes a real disturbance.

The oddest part about a curved TV is the size. TV size is measured from corner to corner diagonally. But does a curved TV get measured in a straight line or does it follow the curve? The answer is a straight line, meaning the screen is actually slightly bigger than suggested.

Brightness

The standard unit of luminance is a candela per square metre (cd/m²) or more commonly called a “nit” (1 nit = 1 cd/m²). Nits are how TVs (and other screens) measure their luminance range. The more nits, the brighter the picture. The ultimate goal of manufacturers is a TV with a range of 0 (black) to 10,000 (white) nits.

TVs are usually turned up very bright in stores to compete with other TVs around them. It’s unlikely you’ll need this level of brightness at home.

Contrast ratio

Check the contrast ratio — the difference between the brightest white and deepest black the screen can produce. You'll see some pretty impressive numbers (such as 25,000:1 and more) in brochures; but 600:1 is usually fine. Let your eyes be the guide. Take a DVD with clear blacks and whites with you, and get the shop to play it.

Also take a good look at the "depth" of the blacks on various screens. Good screens will have more uniformity with their blacks and smooth gradients from black to white.

High Dynamic Range

Think 16 million colours is a lot? Wait until you see 16 billion.

TV manufacturers first competed on screen size — bigger was better. Then resolutions increased until HD became the norm — now the pixel density of 4K TVs has reached the limit of what the human eye can process. The next battleground is “High Dynamic Range” (HDR). This is all about colour; your eyes are capable of seeing far more colours than your TV screen shows.

Colours on a TV can be mapped with 3 values: luminance, chroma and hue. Chroma (often denoted as ‘u’) and hue (‘v’) create the base colour palate and luminance adds intensity. “Colour volume” refers to the level of luminance. An HDR picture has more colours and displays a higher luminance range than a regular HD TV image.

You might have come across HDR on your smartphone or digital camera. These use multiple images in “HDR mode” to improve luminance range and increase image quality.

Picture an erupting volcano. An HDR image captures both the bright tones of the lava and the details of the dark mountain without under- or over-exposing the picture. Similarly, a scene in a forest that might be a flat dark image with few visible details on a non-HDR TV, would abound with depth and life in the HDR version.

Colour volume or luminance shouldn’t be confused with the normal brightness control on your TV. Brightness raises or lowers the intensity of the whole screen, whereas detail stored in an HDR image increases the range of brightness across the screen, raising or lowering the relative intensity down to an individual pixel level.

HDR standards

Television manufacturers have competing standards for HDR but, unlike Blu-ray versus HD DVD back in 2007 or VHS versus Betamax in the 1980s, buying a new TV won’t result in you potentially making an expensive mistake.

Each manufacturer uses different technology to achieve HDR, but HDR-enabled content will work on all of them:

LG’s HDR TVs use Dolby Vision — Dolby’s standard. Dolby Vision has 16 billion colours and footage is encoded with luminance information on a scene-by-scene basis. For comparison, a normal HD TV creates roughly 16 million colours.

Panasonic DX700, DX740 and DX900 models have HDR. However, the DX900 is the only model that meets the UHD Alliance specification (see below) of 1000 nits peak brightness and black level of 0.05 nits.

Sony’s Z-series HDR TVs use its “4K HDR ProcessorX1 Extreme” along with the “Backlight Master Drive” to create HDR images. Moreover, Sony claims the Processor X1 upscales images to HDR by “analysing images in each scene and correcting colour and contrast of each object individually”.

Samsung’s new UHD TVs use HDR 1000, which delivers 1000 nits peak brightness. They also use Quantum Dot Colour, which can create a billion different colours.

UHD Alliance

The UHD Alliance is an industry group of creators — including Netflix and the major film studios, alongside Dolby and Technicolor — and TV manufacturers that created base-levels for what they considered a “good” TV. TVs with an Ultra HD Premium logo meet the alliance’s standards for resolution, HDR, peak luminance, black levels and wide colour range, along with measures for sound.

This standard doesn’t define if a TV is HDR or not, but just if it’s good enough to get the tick of approval.

To get the official tag from the UHD Alliance, an HDR TV must have a minimum of either:

  • >1000 nits peak brightness and <0.05 nits black level, or,
  • >540 nits peak brightness and <0.0005 nits black level

The former means very bright whites with good blacks and the latter means good whites with very deep blacks.

What to watch

In New Zealand, Netflix is the only real player at the moment when it comes to getting your hands on HDR content. So if you have a connection of 25Mbps or faster — VDSL or fibre connections — an HDR TV and have signed up to Netflix’s Ultra HD plan, you’ll be able to watch Netflix’s HDR shows. There are a growing number of Ultra HD Blu-ray discs, though you’ll need a player that supports HDR.

Content can be mastered with particular HDR protocols, so while they’ll look good on any HDR TV, they’ll look their best on a TV that uses the same protocol. For example, Dolby have been collaborating with studios to create Dolby Vision. A range of film and television titles are already available in this HDR format.