Sorry to revive an old thread, but did anyone find a proper solution for this? I dont even have HDR enabled and the 4k streams still go dim.
If your TV supports HDR and it receives a HLG picture source the TV switches into HDR(HLG) mode.
I don’t think this can be disabled on TVs .
I know it can’t on LG TV’s.
Some TVS have a pop up notification to let you know that it has switched colour mode and on some TVs you can press the info button on the remote and it will give you information like aspect ratio, resolution, colour mode etc about the picture source you are viewing.
Also check what mode you SDR is set to depending on your brand of TV you may have different ones like Standard,Sport,Vivid, Game ect.
Same with HDR.
Same with Dolby Vision.
HLG has not got the same amount of colour depth that HDR10 has and won’t look as bright as other HDR10 sources from official streaming apps that use HDR10 and HDR10+ and Dolby Vision.
The reason HDR(HLG) could look dull could be down to a cheap TV with a low nits count.
Your device does not support HDR(HLG)
Poor HDMI cables.
You have adjusted your brightness levels up high on SDR mode and when it switches into HDR (HLG) mode the picture gets duller because each mode has to be set separately manually.
The mode type setting as mentioned above.
It may just be down to the fact that the channel is not actually UHD and it is just 4K SDR.