@Jane.sharman
There are no broadcast 4K channels.
The HD (High Definition) channels - 101 upwards, with some exceptions above 120 - are ‘1K’, which your TV turns into a 4K, also called UHD, Ultra High Definition), picture by inventing three out of every four pixels shown on the screen, based on what it sees on the actual adjacent pixels. This is called upscaling. From HD to 4K is pretty acceptable.
The SD (Standard Definition) channels - 1 to 99 - are about ‘0.25K’ which your TV turns into a 4K picture by inventing 15 out of every 16 pixels shown on the screen, based on what it sees on the actual adjacent pixels. So the TV is having to do a lot more guessing here when upscaling, and the results aren’t as good as HD upscaling.
The engineers probably showed you the TV working one one of the HD channels, but you are possibly watching the SD channels instead?
So if you are watching BBC 1 on Channel 1, try channel 101 instead, BBC1 HD, which is usually the same programme, but a better quality picture.
I say ‘usually’ because the regional news is only on BBC 1, and the HD channel shows a bright red and not very interesting placeholder while this is on.
Something that keeps people on BBC1 because they can’t be bothered to keep switching.
Channels 102/105 don’t do this, but still involve jumping up the EPG, or typing in the extra digits 10, which likewise puts people off.
If you want to see some real 4K, go into the BBC iPlayer and look for His Dark Materials or Black Narcissus. Both these programmes are available in UHD (4K), with HDR (High Dynamic Range), so shiny things and lights on screen are extra bright.
This will show you what detail your TV is capable of.
If this isn’t your issue though, using 1 instead of 101 and so on, please post a picture here of you screen looking low quality, so we can see what it might be.
My favourite bedtime reading is a Sony product manual…
