LED, LCD and plasma TV reviews: Features explained
Interactive TV features guide
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|LCD features explained|
|Screen resolution||This is the number of pixels or lines displayed on the TV screen. Expressed as width x height, the highest screen resolution commonly available is 1920x1080. This is desirable for high-definition material, but it doesn't necessarily mean you'll get the best pictures for watching normal TV broadcasts or DVDs. A good LCD or plasma TV often relies far more on decent digital processing software.|
|Contrast||The difference between how dark and light the LCD or plasma TV will go. A high contrast ratio should mean deeper blacks and whiter whites, with a good range of subtle colour gradients in between. However, it's difficult to compare claims from one brand to the next because of the variety of measuring methods used. And higher numbers do not necessarily mean better TV pictures. Contrast ratio is not a linear value so 12,000:1 is not 'twice as good' as 6,000:1.|
|LCD and plasma||Liquid crystal display (LCD) TV screens come to life when a backlight is shone through the screen's matrix of tiny coloured liquid crystal cells. Digital signals control each cell, letting varying amounts of colour through, building up a picture. A plasma TV display is an array of tiny gas cells sandwiched between two sheets of glass. Each cell acts like a mini fluorescent tube, emitting ultraviolet light which then strikes red, green and blue spots on the screen to build a picture. LCD TVs use far less power than plasmas, but plasma TVs have traditionally sported deeper, richer blacks and better viewing angles. However, LCD technology has improved and it's the quality of the digital processing software, not the technology per se, that will more often than not dictate the quality of the picture.|
|Widescreen||The vast majority of LCD and plasma TVs are widescreen – with an aspect ratio of 16:9 (width x height). However, many small LCD displays are not true widescreen models and can slightly stretch or squash the picture to fit the screen. Typical sizes include computer monitor standards 16:10 and 14:9, or even the old 4:3 box shape. Digital TV is broadcast in a widescreen format.|
|HD TV||HD TV boasts roughly double the resolution of a standard-definition signal, making it more detailed and realistic. It's available on Sky or Virgin for a monthly fee, or free on Freesat. Freeview HD channels will be available in 2010. To watch you'll also need an 'HD-ready' LCD or plasma TV. Not everything on the dedicated HD channels is actually recorded in HD but more programmes are being recorded in HD all the time.|
|1080i||There are two main types of HD picture – 1080i and 1080p. HD TV is broadcast in the 1080i picture format by Sky, Virgin and Freesat. The four-digit number tells you how many horizontal lines make up the picture (standard-definition is made up of 576). The 'i' stands for interlaced, meaning the lines are scanned not one after another, but by every second line to create a field. A field of odd lines and a field of even lines are combined to make a frame, scanned at 25fps (frames per second).|
|1080p||There are two main types of HD picture – 1080i and 1080p. High-definition Blu-ray discs are recorded in 1080p. The 1,080 horizontal lines are scanned progressively, or one after another, making the 1080p image marginally more detailed and realistic than a 1080i image, but the difference is really quite subtle. 1080p is not broadcast because the pictures would simply take up too much space, or bandwidth.|
|15 - 23 inch||Smaller LCD TVs are ideal as a second set for the kitchen or bedroom, but be wary of using smaller sets to watch high-definition material. Sub 26-inch screens will generally not do justice to the extra detail of HD TV. Sound quality also has a link to the size of the screen. Bigger displays can house larger speakers, which will tend to give a better audio performance.|
|26 - 32 inch||For the average living room 32-inch LCD TVs will suffice. 32-inch is the most popular screen size and more akin to the display of a typical conventional CRT. We tend to find 32-inch sets the best size compromise for watching in both standard and high-definition and our Best Buy 32-inch Panasonic TVs currently deliver the best all-round picture quality we've seen. If you favour watching HD TV above anything else – then opt for a bigger screen.|
|37 - 50 inch||Huge screens do justice to the extra detail of high-definition pictures, but may not be the wisest choice if you just want to tune into regular standard-definition Freeview broadcasts. They tend to be less forgiving to the digital processing side effects more apparent on standard-definition, especially if you sit too close. Sitting 2.8 metres from the TV has traditionally been considered the ideal viewing distance, but the bigger the screen the further away you should sit.|
|15 - 23 inch||The HD-ready label means the TV meets the minimum criteria for displaying 1080i HD TV signals – so the TV is ideal for watching HD TV from Sky, Virgin or Freesat. Most new HD-ready television sets will also process the 1080p HD signal – the marginally more detailed HD format recorded on Blu-ray discs. If the TV does not support 1080p, it simply switches to 1080i. Virtually all LCD and plasma TVs are at the very least HD-ready.|
|HD-ready 1080p||The LCD or plasma TV can process a 1080p signal and has a high screen resolution of 1080 horizontal lines (1920x1080). In theory, this should mean even better HD pictures. In practice the quality of the TV picture has more to do with the picture processing software, than just the screen resolution. Similar-sounding and looking logos such as, HD Full, 1080HD or 1080HD-ready are also commonplace, but exact meanings differ between manufacturers.|
|100Hz and 200Hz||Most TV pictures are broadcast or recorded at 50Hz – that's 25 frames per second. In an attempt to reduce motion blur, many LCD and plasma TVs feature 100Hz processing software. This basically doubles the number of frames on screen per second. The very latest LCD and plasma TVs boast 200Hz processing software, quadrupling the original frame rate, and placing 100 frames on the screen every second.|
|Digital processing software||Many of the fancy-sounding labels you'll see on these TVs refer to the digital-processing software, or engines, used by LCD and plasma televisions. For instance, Samsung, uses its Digital Natural Image engine (DNle), LG its Dual XD or simply XD engine, Panasonic uses Vreal2 and Philips either Pixel Plus HD, Perfect Pixel HD or simply Pixel Plus. Decent processing software usually equals good pictures. For instance, many Sony LCD TVs feature the Bravia2 processing engine – most sport good pictures.|
|Scart inputs||HDMI sockets are designed for connecting high-definition equipment such as Blu-ray players. Connecting standard DVD players with HDMI will rarely improve the picture. Most HDMI sockets support a Consumer Electronics Control (CEC) feature. This allows you to control other CEC-enabled AV equipment connected together by HDMI, via just one remote control. Different brands give CEC different names, including Anynet+ (Samsung), Bravia Sync (Sony), Kuro Link (Pioneer), Simplink (LG) and Viera Link (Panasonic).|
|Audio outputs||Red and white phono sockets allow you to connect your LCD or plasma TV to a stereo amplifier – for improved hi-fi sound. Digital coaxial (wire) and optical (fibre optic) carry both stereo or surround sound signals. Make sure your surround-sound system input matches the output on your LCD or plasma television. Many TVs feature virtual surround sound: they mimic the effect using the two main speakers, but this is usually disappointing.|
|Memory card slots and USB ports||Many LCD and plasma TVs are equipped with memory card slots that let you plug the card from your digital camera directly into the TV. More common are USB ports for connecting memory sticks or digital equipment. Either way, the picture quality is typically excellent and many manufacturers, such as Sony, design their TVs to look like picture frames. As an added bonus, the USB option sometimes allows playback of MP3 music files or digital video files.|
|Eco modes||Many new LCD and plasma TVs have eco or energy-saving settings. Occasionally, this can be slightly misleading and may refer only to an option to switch off the front panel LED – making a negligible power saving. Some television manufacturers have also taken to adding a quick-start standby mode. This allows the TV set to be turned on marginally quicker than from regular standby, but often uses considerably more power. Some energy-saving modes can simply involve switching the wasteful quick-start option off.|
|Ambient light sensor||If selected, an ambient light sensor will automatically adjust the brightness of the LCD TV's backlight, according to how dark or light the room is. In dark conditions, the most efficient sensors can dramatically reduce power consumption – slashing a typical 100-watt reading for a 32-inch TV screen in half. Plasma TVs do not feature backlights but can still have ambient light sensors. The sensor automatically adjusts the brightness of each gas cell that makes up a plasma display picture.|
|Radio blanking||Some LCD and plasma TVs can blank the screen when tuned to a digital radio channel. It's still not quite as green as listening via a typical tabletop DAB radio, but can significantly reduce energy use. For larger TVs, radio blanking can slash more than 100 watts off the total power used. On smaller television sets the effect is less dramatic. Sony, Sharp and Pioneer TVs usually include a screen-blanking feature.|
|On/off switches||Many new TVs have 'soft' on/off switches rather than traditional mechanical buttons. These have the advantage of being less prone to breaking. However, the 'soft' switch requires an electrical current to turn the set back on – meaning many LCD and plasma TVs use power even when they are switched off. The power used is low (less than 1 watt), but if you truly want to switch your TV set off, the only choice may be to switch it off at the mains.|
Flat panel TVs
The beauty of LCD, LED and plasma or flat panel TVs is that they're much slimmer than older, 'big-box' televisions (anything from 1cm to about 20cm deep, compared with 50cm to 60cm deep for a 32-inch big-box TV set with a cathode ray tube).
Flat panel TVs generally take up less space, have bigger screens, can be mounted on walls and look stylish.
They sport high resolution (HD) screens. HD picture quality on the latest TVs can be stunning, but sound quality is often disappointing. The trend towards thinner and thinner models leave less room for good speakers.
HD TV Guide - find all more about high definition.
Smart TV is a catch all term for TVs with internet features, also known as ‘internet TVs’ or ‘connected TVs’. Each TV manufacturer has its own smart TV system, which has a range of apps for different services – common apps include BBC iPlayer and YouTube.
Smart TV - find out more about smart TV
Many new TVs can display a 3D picture. To watch in 3D, you need a pair of 3D glasses and some 3D content. Sky has its own 3D channel, while Virgin Media and BT Vision both offer a selection of on-demand 3D content. You can also watch 3D films on a 3D Blu-ray player.
3D TV essential guide - all you need to know
Logos and labels on LED, LCD and plasma TVs
LED, LCD and plasma TVs with digital processing
Many of the fancy-sounding labels refer to the digital picture processing software used by LED, LCD and plasma televisions.
For instance, Sony uses X-Reality, Samsung uses Wide Colour Enhancer Plus.
Good digital picture processing software usually results in good picture quality, no matter whether the TV is LED, LCD or plasma, Full HD or not.
This is the number of pixels or lines displayed on the television screen. Expressed as width x height, the highest screen resolution currently available is 1,920x1,080, often described as Full HD.
This is desirable for use with HD content, but it doesn't necessarily equate to the best pictures for watching standard definition TV broadcasts or DVDs.
100Hz and 200Hz processing
Most TV pictures are broadcast or recorded at 50Hz – that’s 25 complete frames per second.
In an attempt to manipulate the picture and create the illusion of smoother motion, many LED, LCD and plasma TVs feature processing at 100Hz or above. 100Hz doubles the number of frames on screen to 50. Some TVs have 200Hz processing software, quadrupling the original frame rate and placing 100 frames on the screen every second.
Our tests have shown, however, that this smoother motion doesn't always appear realistic.
Processing above 200Hz is often measured in a different way, so it's not always the case that the bigger the number the better.
The contrast ratio is the difference between how dark and light the LCD or plasma TV display will go. A high contrast ratio should mean deeper blacks and whiter whites, with a good range of subtle colour gradients in between.
However, it’s again difficult to compare contrast ratio claims from one manufacturer to the next because of the variety of measuring methods used.
LED, LCD and plasma screen features
LED and LCD TVs feature backlights – lights at the rear or edge of the screen which illuminate the picture.
Many LED and LCD TVs have dynamic backlights which adjust their intensity according to the content on the screen.
For instance, if there’s a dark image on screen, the TV will automatically dim the backlight. This should make the image look darker and avoid the washed out appearance that might otherwise occur.
On the downside, we've occasionally noticed that dynamic backlights can sometimes be slow to react to the changing content on screen and it’s possible to see them ‘working’, so you notice the picture brightness dim moments after the screen has switched to a dark image.
Plasma TVs do not have backlights – instead, they alter the brightness of the individual gas cells that make up the picture, saving power and creating much the same effect.
Picture-in-picture displays a small image in the corner of the TV screen while you watch the main image.
Some TVs let you watch another broadcast channel in this way – so you can check the progress of a football match, say.
However, with many TVs Which? has tested, the picture-in-picture system lets you monitor only those pictures from external equipment, such as a Blu-ray player or set-top box.
Electronic programme guide (EPG)
Found on all new LED, LCD and plasma TV, this is an on-screen channel guide showing programming for the week ahead – a bit like having an onscreen copy of the Radio Times at the touch of a button.
The style and format of an EPG depends on the particular model of TV, but most show programmes at least seven days ahead, plus a 'Now and Next' option.
The best EPGs show several channels over a fixed time period, say two hours, making comparing channels and planning an evening's viewing more convenient.
Some also display a handy 'picture-in-picture' of the current channel in the corner of the TV screen.
TV energy-saving features
Ambient light sensors
An ambient light sensors - the most ingenious of all energy-saving TV features - can help you make big energy savings. The sensor adjusts the backlight of the TV according to how dark or light the room is, and if you watch the TV with the lights off they can slash power use by around 30-50%.
Nearly all TVs 32-inches of over have an ambient light sensor.
Most TVs can blank the screen when tuned into digital radio channels, and switch themselves off if left idle for too long. Sony has also developed energy-saving presence sensors that turn the picture off if it senses that nobody is in the room. There is even a screen warning to alert particularly static couch potatoes.
Best TVs for low energy use - find out which types use the least amount of energy
Accessibility features on LCD and plasma TVs
An additional narration for visually-impaired people that describes significant visual information, such as body language and scenery.
Many TV programmes on the main channels now have audio description.
If you have problems distinguishing human voices from background noise (such as music) on your TV, built-in voice-enhancement software could help. LG's 'Clear Voice II' is one such example.
Other TV audio features
Automatic volume control
Adverts can sometimes seem louder than the programme you’re watching.
To combat this, TV manufacturers have developed automatic volume-control (or levelling) software.
Claims vary between brands, but they typically involve compressing the sound’s dynamic range to prevent adverts from sounding too loud, or they might balance sound levels between channels.
Sockets and plugs on LED, LCD and plasma TVs
This is the socket for your aerial and allows the broadcast signal to be received by your tuner.
A high definition video and audio input used for connecting HD equipment, such a Blu-ray player, HD camcorder, games console or set-top box.
A few small TVs have only one HDMI port, but most TVs have three or four. If you need more, you can buy an HDMI switching box for £10 or so to expand your TV's capacity.
Most HDMI sockets support some sort of consumer electronics control (CEC) feature. This allows you to control other bits of CEC-enabled AV equipment, connected together by HDMI, via just one remote control.
Different brands give CEC different names, including Anynet+ (Samsung), Viera Link (Panasonic) and Bravia Sync (Sony).
Manufacturers imply that their TVs will only link with AV equipment from the same brand. Basic CEC functionality (on/off) usually works between brands, but more advanced functions (accessing menu controls) may only work with ‘own brand’ products.
An HDMI socket often lets you connect your laptop – effectively turning your flat panel TV into a large monitor.
Scarts allow you to standard definition connect equipment like DVD recorders and video cassette recorders to your television. Most new TVs come with one Scart socket.
If you need more, you can buy a Scart switching box for £10 or so.
For the best picture, look for Scarts that support the high-standard RGB signal. This splits the video signal into its red, blue and green components to give an improved picture.
An analogue VGA input, sometimes marked 'PC' on the TV, that lets you connect your PC. Connecting via VGA doesn't provide the same picture quality as HDMI, but is useful if your computer doesn't have an HDMI output. Most desktops and older laptops don't.
These red and white sockets allow you to connect your LED, LCD or plasma TV to a stereo amplifier and speaker system – useful if you want to achieve better sound quality.
Many new TVs lack these sockets, though you can sometimes connect the TV to a stereo amplifier using the headphone output, or a digital to analogue converter connected to the digital audio output.
Digital audio outputs
Many LED, LCD and plasma TVs have 'virtual' surround sound: they mimic the effect using the two main speakers, but this is usually disappointing. The best solution for good quality surround sound is a dedicated home cinema system.
If you want to connect your LED, LCD or plasma TV directly to a surround-sound system there are two types of digital connections – coaxial (wire) and optical (fibre optic).
Make sure your surround-sound system input matches the input on your television
Some TVs have up to three USB ports. These can be used to view photos and videos on the TV, or sometimes to insert an external hard drive for recording programmes.
Recording programmes in this way is usually less convenient than using a PVR, but it's a useful money-saver if you don't already have a PVR.
Useful if your TV doesn't have wi-fi, this allows connection to a computer network in your house, letting you stream audio and video content straight to your LED, LCD or plasma TV. This can often be done using DLNA.
An ethernet port can sometimes also be used for connecting a smart TV to the internet.