Resolution: Ultra HD vs Full HD
There are two resolutions to choose from right now: Ultra HD (also known as 4K), and HD. Ultra HD TVs carry 3840 x 2160 pixels, while HD TVs carry 1920 x 1080 pixels. This means Ultra HD TVs have four times as many pixels as HD ones, and so can deliver pictures with much more resolution.
With native 4K sources starting to become more common now (Netflix, Amazon, Ultra HD Blu-ray and Sky Q in the UK) and the prices of 4K TVs plummeting, we’d generally recommend that you buy a 4K TV even if you don’t currently have any access to 4K content, especially if you’re looking at a TV of 50 inches or more.
While we’d recommend 4K for a main living room TV now, though, HD TVs can be good bargains for second rooms.
Brightness and nits
A screen’s brightness (as measured in nits) has started to become a big deal with the arrival of HDR, with many HDR proponents – including, especially, Dolby – stating that we’re about to enter a ‘nit race’ where TVs push to constantly get brighter.
The brightest LCD TVs (Samsung’s upcoming ‘QLED’ models) can get as bright as 2000 nits. The 2017 generation of OLED TVs are reckoned to get to between 800 and 1000 nits.
High dynamic range (HDR) is the latest technology to arrive on the TV scene. HDR TVs are able to produce pictures that contain much more brightness and contrast than normal TVs, so long as they are fed HDR content that contains this extra luminance data.
All current HDR TVs also support wider color spectrums (often described as wide color gamut, or WCG – essentially meaning that) than most non-HDR TVs - which is handy, as pretty much all HDR content also carries wide color spectrum picture data.
There are currently three types of HDR. HDR10 is the industry standard, and all TVs support this. Dolby Vision adds an extra layer of information that tells a TV how to render pictures on a scene by scene basis. Only some brands – most notably LG, Vizio, TCL and (via an upcoming firmware update to some models) Sony – support this.
Finally there’s Hybrid Log Gamma (HLG), designed for HDR broadcasts. The majority of TV brands have pledged support for this via firmware updates in the course of 2017.