Portable TVs: Features explained
The trend in TVs is towards the big, with screens over 40-inches fast becoming the norm. However, for many of us a second set in the bedroom, or kitchen, should be a little more discreet.
LCD TVs offer the widest number of screen size options
The beauty of small LCD TVs (with screen sizes between 15 and 23-inch) is they're much slimmer than conventional TVs – about 10cm deep compared with around 40cm for a portable conventional set with a cathode ray tube.
Compared to larger flat-panel sets they have other attractions too. Typically the smaller the screen the less power it uses. For instance, on average a 32-inch LCD will use over 100 watts of power and a 42-inch plasma around double that. Smaller LCDs in the 15- to 23-inch category typically use around 40 to 50 watts of power when switched on.
Plus if you want to mount your TV on the wall, you usually have to buy brackets separately. A wall kit for a 42-inch flat-panel plasma can set you back up to £300. Brackets for LCD TVs of 26-inch and under are a tenth that price.
Screen features
Native/screen resolution
This is the number of pixels or lines displayed on the screen (width x height). Smaller LCD TVs tend to have lower screen resolutions than their big screen cousins. But fear not – high screen resolution is not a guarantee of a great picture. All LCD TVs use digital processing software to put a picture on screen and unless this is spot-on the process can lead to unpleasant side effects.
Aspect ratio
This is the shape of the screen (height x width). Virtually all full-size widescreen TVs have an aspect ratio of 16:9 - matching the 16:9 format of digital TV broadcasts. 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 typical; computer monitor standards 16:10 and 14:9, or even the old 4:3 box shape reminiscent of traditional CRT sets.
Auto-format switching
It's a good idea to choose a TV that automatically alters how different broadcasts are displayed – for example, showing standard (4:3) broadcasts with black bands on either side so the images aren't stretched out of proportion. Most widescreen TVs will do this. Some small 16:10 models can also be set to display a 16:9 picture with black bands at the top and bottom of the screen - avoiding the need to stretch the broadcast picture to fit.
High-definition television (HDTV)
HDTV pictures have roughly double the resolution of a standard-definition signal, making them more detailed and realistic. HDTV is available on Sky and Virgin for a monthly fee, or via Freesat for free. HDTV can look fantastic on bigger TVs but a smaller LCD will struggle to do justice to all that extra detail.
1080i and 1080p
These are the two main types of HD picture. HDTV is broadcast in 1080i, but Blu-ray discs are recorded in 1080p. The difference in quality is very subtle and difficult to spot on a small screen LCD.
HD-ready
A HD-ready label means the TV meets the minimum criteria for displaying 1080i HDTV signals. However, many smaller LCD TVs which boast the necessary screen resolution and sockets are not the correct widescreen aspect ratio. An HD-ready TV should be 16:9.
Audio description
This is an additional narration for visually-impaired people that describes significant visual information, such as body language and scenery. The service is available on Sky and Freeview. The number of TVs which can decode Freeview audio description is growing all the time – and it is now a standard feature on the best brands.
Text and digital text
RF input
With a set-top box or integrated digital TV, you can access the digital text services available on some digital channels. These look like internet pages, and some let you watch an inset of the TV picture at the same time.
Power saving features
Radio blanking
Some TVs can blank the screen when tuned to a digital radio channel, saving power in the process. It’s still not quite as green as listening via a typical tabletop DAB radio but can significantly reduce energy consumption. On average a TV with radio blanking activated consumes around 20 watts. For larger TVs, that can slash around 100 watts off the total. On smaller sets the effect is less dramatic but power use is still typically cut in half.
Ambient light sensor
If selected an ambient light sensor will automatically adjust the brightness of the TV back-light, 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 screen in half. We've yet to test a light sensors on a smaller screen LCD TV.
Sockets and plugs
RF input
This is the socket for your aerial and allows the broadcast signal to be received by your tuner.
Scarts
Scarts are the best way to connect equipment such as DVD players and set-top boxes to your TV. Most TVs now come with two Scart sockets. If you need more, you can buy a Scart switching box for £10 or so to expand your TV's capacity but if your TV has a built-in Freeview tuner then you'll probably only need one Scart socket, to plug in a DVD player for instance.
For the best picture from DVD players, 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.
Composite video and s-video input
If you're short of Scart inputs composite video and s-video can provide an alternative. S-Video signals are split into colour and brightness but are slightly inferior to Scart RGB.
Composite video (usually a yellow phono socket) is the lowest quality video connection. Both let you plug other AV equipment, such as camcorders and games consoles, directly into your TV.
HDMI input
If you're interested in HD, this is the high-capacity input for high-definition video and audio signals. Most small-screen LCD TVs have one HDMI socket for connecting a HD receiver box or even HD Blu-ray player. However, widescreen TVs sporting displays of at least 26-inches are far more suited to watching ultra detailed high-definition pictures.
DVI input
This is the standard digital input used for high definition video. Unlike HDMI, it cannot carry audio signals and had been largely phased out in favour of the latter.
VGA input
This can effectively turn your TV into a PC monitor. HDMI sockets can sometimes be used as a digital alternative – but they have to support computer screen resolutions (these differ from standard TV resolutions). If not chances are the picture will be over-scanned and partially missing from the screen.
Component video input
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.
VGA input to connect your PC
Component is a useful high quality connection for games consoles but not so suitable for other types of AV equipment (DVD players, VCRs, set-top boxes). Unlike Scart sockets they don't carry the widescreen switching signal.
Phono sockets
These red and white sockets allow you to connect your TV to a stereo amplifier. Connecting to your hi-fi delivers far superior audio results than the built-in speakers on many TVs. As a rule of thumb the smaller and cheaper the TV is, the lower the quality of the in-built speakers
Surround sound
Many 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.
Optical output
Coaxial and optical outputs
If you want to connect your 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 TV. However, there is vir4tually no digital surround-sound broadcast on Freeview, although both optical and coaxial connections can carry stereo signals.
Common interface (CI) port
Setanta Sports and Top-Up TV are additional subscription services to Freeview and require a smart card to watch. Most Top-Up TV viewers will use a special Top-Up receiver/PVR but Setanta viewers can use any IDTV, set top box or PVR that has a card reader.
The card reader fits into the CI port – and according to a European directive this CI port must be present on any TV with a DVB-T (Freeview) tuner. Occasionally we do come across models without a CI port, which won’t be of any interest to most consumers but nevertheless makes the product technically illegal.
The card reader or CAM (conditional access modules) which slots into the CI port costs about £40-£50.