TV screen technology explained
TV jargon buster
By Andrew Laughlin
Article 8 of 8
Buying a new TV can be an expensive purchase, and there's nothing worse than trying to decipher reams of jargon to work out if it's worth spending more on the latest technology.
Bewildered by back-lighting, confused by CRT or disoriented by digital processing? We'll walk you through the key terms you need to know about when shopping around.
100Hz and 200Hz processing
Standard 50Hz TVs are fine for watching broadcast TV, as it is recorded or broadcast at 50Hz - that’s 25 complete frames per second. In an attempt to manipulate the picture and create the illusion of smoother motion, many high-end TVs feature processing at 100Hz or even 200Hz, doubling or quadrupling the amount of times the image is produced on screen.
Our tests have shown, however, that this smoother motion doesn't always appear realistic to the eye and people can feel they get a better picture after turning such ‘enhancement’ features off.
1080i and 1080p
There are two main types of high-definition (HD) picture: 1080i and 1080p. HD TV is broadcast in 1080i, while high-definition Blu-ray discs are recorded in 1080p, which is marginally more detailed and realistic. This is because on 1080p, the 1,080 horizontal lines are scanned progressively, or one after another. With 1080i, even lines then odd lines are scanned alternately to make up the picture, although the difference is really quite subtle.
3D TV offers a greater sense of depth than standard 2D television, making films and TV programmes appear as though they are ‘coming out of the screen’. To watch 3D TV, you need special glasses and there are two types - passive and active.
‘Passive’ glasses are light and cheap, similar to the ones used in 3D cinemas. ‘Active’ ones are bulkier and more expensive, although they offer the best viewing experience. 3D TV hasn’t really taken off due to the lack of content and the fact many people find wearing 3D glasses uncomfortable. There are glasses-free 3D TVs, but they're mostly prototypes. For more on 3D, please see our What is 3D TV? guide.
4K TVs - also referred to as ultra-HD or UHD - have four times the pixels of ‘normal’ HD 1080p TVs. Most of the big manufacturers have now launched 4K TVs, and they usually have screens 40-inches or over, as you need a larger display to really appreciate the extra detail in the picture. There's not much 4K content right now beyond some internet streaming services, but 4K Blu-rays are expected to arrive in 2015 and eventually we'll see some 4K TV channels launch. For more on 4K, please see our What is 4K TV? guide.
An arrangement of six speakers, one of which is a low-frequency subwoofer speaker, used to create surround sound. For more, please see Surround Sound.
Ready to see great TVs? Browse hundreds of models of all types, prices and brands with our TV reviews
Ambient light sensors
Available on nearly all TVs that are 32-inches or over, these sensors adjust the backlight of the screen according to the amount of light in the room. They can provide big energy savings, slashing power by around 30-50% when the TV is running with the backlight off.
This is the shape of the screen measured as ‘width:height’. Most TVs are now widescreen with an aspect ratio of 16:9. Digital TV is broadcast in a widescreen format.
This offers additional narration of TV for visually impaired people by describing significant visual information, such as body language and scenery. Most of the main channels now have audio description on at least some of their programmes. If you have problems distinguishing human voices from background noise, such as music, many TVs also offer voice-enhancement software.
Automatic volume control (AVC)
Software in TV sets that prevents adverts from sounding too loud by compressing the dynamic range or better balancing the sound levels.
If you leave your TV switched on when not in use, this handy energy-saving feature switches it onto standby mode after a set period of idleness.
Back-lit LED TVs
Also referred to as direct-lit, back-lit LED TVs have LED lamps spread across the entire rear of the screen. They aren't as slim as edge-lit models, but the consistency of lighting spread should be much better.
Black level control
This adjusts the pictures’ black level, which is useful when watching movies with particularly dark sequences.
A high-definition DVD format developed by Sony. A Blu-ray disc can hold nine hours of high-definition (HD) video and around 23 hours of standard-definition (SD) video on a 50GB disc. Blu-ray pictures are recorded in 1080p, which is subtly more detailed and realistic than the 1080i HD broadcast signal. Find out How to buy the best Blu-ray DVD player.
This is a high-quality video input made up of three sockets coloured red, green and blue. Also known as YPbPr, it splits the video signal into three separate parts for an improved picture. However, component connections are still not widely used on AV equipment and, unlike Scart sockets, they do not carry the auto-format switching signal.
The contrast ratio is the difference between how dark and light the TV display will go. A high-contrast ratio should mean deeper blacks and crisper whites, with a good range of subtle colour gradients in between. Contrast ratio is considered vital for a great TV picture, but it’s not a linear value so 12,000:1 is not ‘twice as good’ as 6,000:1.
Cathode ray tube - the technology behind old-style ‘big-box’ TVs. Traditional cathode ray tube TVs have now been superseded by flat-panel televisions.
Many fancy-sounding labels on TVs refer to the digital processing software used by manufacturers to enhance the picture. Sony uses X-Reality Pro, Samsung has Wide Colour Enhancer Plus and Panasonic boasts the Hexa engine. This software can improve the picture, but be aware that it can also change it for the worse at times.
An industry-wide standard developed to allow the sharing of digital media, such as photos, videos and music, between computers, mobile phones, TVs and other devices in and around your home. Want to know more? Read our dedicated guide to DLNA.
Digital theatre system is a surround-sound standard used in home cinema systems.
LED and LCD TVs feature backlights - lights at the rear or edge of the screen which illuminate the picture. Dynamic lights adjust according to the content on screen; eg, for a dark image, the TV will automatically dim the backlight. However, you can occasionally see backlights ‘working’, in that the TV visibly dims, which can be off-putting. Plasma TVs don’t have backlights.
Edge-lit LED TVs
Edge-lit model LED TVs have LED lights just around the edge of the screen, enabling them to super-slim. Early edge-lit models had problems with inconsistent lighting of the screen, and patchy colours. While you can still find a bad one, the technology behind edge-lit panels has improved significantly in recent years.
Electronic programme guide (EPG)
Found on modern LED, LCD and plasma TVs, this on-screen channel guide shows the TV schedule for the week ahead, allowing you to select programmes, get more information and set recordings if you have a PVR.
If your TV doesn't have built-in wi-fi capability, this port allows you to use an Ethernet cable to connect a Smart TV up to the internet.
The general term used for LCD , plasma and LED technologies.
A subscription-free digital satellite TV service. To watch it you'll need a Freesat set-top box, a satellite dish and ideally an HD-ready TV. Freesat offers more channels than Freeview.
A subscription-free digital TV service that provides television through an aerial. Virtually all new TVs come with Freeview built in.
Similar to Freeview, with a handful of HD channels thrown in. Some new TVs come with Freeview HD built in. Alternatively, you can buy a Freeview HD set-top box to access it.
Full HD and HD-ready
Screen resolution is the number of pixels, or lines, displayed on the TV, expressed as ‘width x height’. Full HD screen resolution is 1920 x 1080p and these TVs have superior picture quality when watching a Blu-ray movie. Cheaper, 'HD ready' TVs have the minimum screen resolution to display a broadcast HD picture, but Blu-ray movies will not be as sharp as Full HD.
A high-definition video and audio input used for connecting HD equipment, such as a Blu-ray player or a Sky HD box. Small screen TVs tend to have only a few, but most larger sets have three or four. An HDMI switching box can be used to add more ports. For more on this, please see our Buyer's Guide to HDMI Cables.
'HD ready' is a labelling scheme introduced by the TV manufacturers' organisation, the European Industry Association for Information Systems (EICTA). The label means the TV has the minimum screen resolution and digital sockets to receive and display a broadcast HD picture. TVs labelled HD ready tend to have 768 horizontal on-screen lines, but HD-ready 1080p models have 1080 horizontal lines.
High-definition television (HD TV)
HD TV transmits a high-definition TV signal with roughly twice the standard picture resolution as normal standard-definition television. More HD channels are being added all the time, with Sky offering the most.
Liquid crystal display (LCD) TVs use lamps to shine light through liquid crystal cells in the TV's panel, letting varying amounts of colour through to create a picture.
LED TVs are the same as LCD sets, but the back-light lamps are replaced by tiny light emitting diodes (LEDs), which illuminate the screen for the picture to be formed. LED TVs are typically slimmer and more energy efficient than LCD ones.
This technique, also known as 'micro dimming', varies the backlight in different parts of the screen to give darker, richer blacks and brighter whites where needed. It was originally found mostly in back-lit LED TVs, but TV manufacturers have now found ways to incorporate similar technology into their edge-lit models, meaning you're not missing out by buying one - and they're usually cheaper.
The number of pixels or lines displayed on the screen (width x height). The highest screen resolution commonly available is 1920 x 1080. This is desirable for HD TV, but doesn’t necessarily mean you’ll get the best picture for standard TV broadcasts or DVDs.
Organic light emitting diode (OLED) TVs don’t need a backlight and so can be thinner even than LEDs, and display deeper black levels than any current screen type. However, OLED TVs only recently emerged onto the market and are very expensive. For more on that, please head to our What is OLED? guide.
Optical digital output
If you want to use surround sound, there are two types of digital audio connection: coaxial (copper wire) and optical (fibre optic), or TOSLINK. Both connections can carry stereo signals, but make sure you hook up the right inputs on both your surround sound system and the TV.
Picture-in-picture displays a small image of another channel or DVD in the corner of the screen while you watch the main image or use on-screen menus.
Tiny gas cells are sandwiched between two sheets of glass, each emitting ultraviolet light that strikes red, green and blue spots in the screen to make up the picture.
A programmable video recorder (PVR) allows you to set recordings of live TV programmes using an on-screen menu and then choose to watch, keep or delete them. Some PVRs let you store up to 1TB of content and even pause live television. More and more TVs these days have PVR functionality built-in to the set, meaning you can attach a hard disk drive into the USB port and then access many of the features of a separate PVR. Find out How to buy the best PVR or set-top box.
An aerial socket that allows the broadcast signal to be received via the TV's tuner.
Scarts allow you to connect standard-definition equipment, such as DVD recorders or VHS recorders, if you still have one. New TVs come with just one Scart socket, if any, as most modern equipment is now connected via HDMI.
A memory card slot allows you to view photos, or videos on the TV, although very few TVs offer one these days.
Sound bars are long, often tube-link speaker systems designed to boost the sound of a TV by creating a stereo effect using a single cabinet. They have become more popular in recent years due to typically poor sound in modern, flat panel TVs. Interested? Find out How to buy the best sound bar.
Smart TVs connect to the internet via an ethernet connection, Wi-Fi or an external device (such as a set-top box or games console) to give you access to a range of extra services on the TV.
You can stream movies on Netflix, catch up on TV shows via BBC iPlayer, download games, make Skype calls, interact with friends on Facebook and Twitter, or even surf the web using a browser. For more, see our What is smart TV? guide.
These red and white sockets connect your TV to a stereo amplifier and speaker system, which can be useful if you want to improve the sound quality. Most new TVs lack these sockets, although you can use the headphone output, or a digital-to-analogue converter connected to the digital audio output instead.
An arrangement of speakers designed to create a more immersive sound wrapping itself around the viewers. For 5.1 surround sound, you'll need five speakers and a low-frequency subwoofer – hence the ‘five plus one’. For 6.1 and 7.1 surround sound, you'll need to add one or two more speakers respectively. You hook a surround sound system up to your TV using a digital coaxial or digital optical connection (for more, see Sockets).
A low-frequency subwoofer is a complete speaker system dedicated to reproducing the low-pitched audio, bass sound.
Some TVs have one or more USB ports that can be used to connect USB devices, such as USB memory sticks for viewing photos on the TV, or external hard disk drives for a TV's PVR functionality.
An analogue VGA input - sometimes marked 'PC' on the TV - allows you to connect your PC or laptop to the TV if it doesn’t have an HDMI output.
Video on-Demand (VOD)
VOD services allow you to 'stream' live and on-demand video on your TV, or in some cases 'download' programmes to watch later. Popular services include BBC iPlayer, Netflix and Sky Go. Most smart TVs should allow you to access these services, but you'll often find more on offer with an Internet TV box.