4K and HDR, explained without the marketing

4K means roughly 3840 by 2160 pixels — four times as many as 1080p. That is all it means. More pixels help when the screen is large and you sit close to it, and help less and less as either of those stops being true.

At two and a half metres from a 55-inch television, most people cannot reliably tell 4K from a good 1080p source in a blind test. That is not a criticism of 4K; it is a description of human eyes.

High dynamic range is about how bright the brightest part of the picture can be while the darkest part stays dark, and how many colours sit between them. This is the change you can see from across the room.

A sunset in HDR keeps detail in the sky and in the shadows at the same time. In standard range, one of the two has to give. That is a far bigger visual difference than doubling the pixel count.

HDR10

The baseline open standard. One set of brightness instructions for the whole film.

HDR10+

Adds per-scene instructions, so a dark scene and a bright one are each mapped properly.

Dolby Vision

A licensed alternative to HDR10+, doing broadly the same job.

HLG

The broadcast format, designed so one signal serves both HDR and standard televisions.

1. 1Use the HDMI port on your television that is rated for full-bandwidth 4K. On many sets only one or two are.
2. 2Turn on the enhanced or deep colour setting for that port. It is off by default on most televisions and it is the single most common reason HDR looks wrong.
3. 3Use a high-speed HDMI cable. Older cables carry 4K but silently drop HDR metadata.
4. 4Leave the box on Auto and let it negotiate. Forcing a mode is a troubleshooting step, not a setup step.

Do all four and the picture will be as good as your television can make it — which, for HDR, is mostly a question of how bright the panel gets.