There are two types of TV technology you need to understand: LCD and OLED. Plus there a couple of important variations on the LCD side.
A key point to consider if you decide to buy an LCD TV is how the LCD panel is lit, since this can have a big impact on the contrast the screen is capable of.
Some use lights mounted on the edge of the screen firing across it (aka edge-lit panels), while some use lights mounted directly behind the screen. Generally speaking, TVs with lights behind the screen deliver better contrast than edge-lit models. But these models don’t generally feature such slim designs, tend to cost more, and often use more power.
One final option to consider with LCD TVs is local dimming. This sophisticated feature allows a TV to output different amounts of light from different sections of its edge or direct lighting arrays, and can dramatically improve contrast.
LCD/LED TVs use panels of liquid crystal pixels illuminated by external light sources. The liquid crystals rotate round to let through the amount of light needed to illuminate pictures correctly, with external filters creating colour.
The main advantage of LCD TVs are brightness, affordability and durability. Their main disadvantages are limited viewing angles and difficulties controlling light in the picture due to the use of external light sources.
There are two types of LCD panel: IPS and VA. IPS types are predominantly made by LG Display, and feature in all of LG’s LCD TVs, plus some (usually affordable) models from other brands too. VA panels are more widely used, and are made by a variety of manufacturers.
IPS panels offer slightly wider viewing angles than VA panels, but struggle with contrast. VA panels up to this point feature narrower viewing angles, but generally produce much better contrast.
OLED TVs use a system of organic phosphors in self-emitting pixels to enable each pixel to generate its own light, completely independent of its neighbours. This allows for vastly superior contrast and light precision to what you can get with even the most advanced LCD TV. It also means OLED TVs can be watched from much wider viewing angles than LCD TVs without colour or contrast reducing. These features have made OLED popular with many serious AV fans.
However, there are issues with OLED TVs. First, while prices have dropped over the past couple of years, they’re still substantially more expensive than typical LCD TVs (though some are now cheaper than high-end LCD TVs).
Second, OLED TVs currently can’t get nearly as bright as LCD TVs, something that could become an issue with HDR content.
Finally, there have historically been issues with lifespan and image retention (where bright image elements can ‘burn’ into the screen’s phosphors if left on for too long). However, LG, the main manufacturer of OLED screens, claims to have fixed these lifespan/image retention issues, and we haven’t seen any evidence recently that might counter those claims.
Some (usually high-end) LCD TVs have started to use Quantum Dot technology to deliver wider colour ranges than you can get with normal LCD panels. Quantum Dots are tiny particles ranging from two to 10 nanometers in size, with each size capable of emitting a different colour. Using them allows LCD TV makers to avoid colour filters and white LED Backlights – two things that typically limit an LCD TV’s colour performance.
Samsung is the biggest advocate of Quantum Dot technology, with its 2017 ‘QLED’ models using a new metal-coated type of Quantum Dot that can produce a much wider colour range, more brightness and a wider viewing angle than traditional Quantum Dots. Quantum dot TVs are generally markedly more expensive than normal LCD TVs, though.
There are alternatives to Quantum Dots when it comes to expanding colour range. Some TVs – including Sony’s recent Triluminos models – use wide-range phosphors. LG, meanwhile, will be using Nano Cells in its high-end LCD TVs for 2017. These alternatives to Quantum Dot technology use same-sized dots just one nanometer wide in conjunction with normal colour filters – a combination which LG claims enables its new Super UHD TVs to deliver better contrast and more balanced colours.