Confused why 4K reencode fails while lower-res don't

[Perenista]

If I am not mistaken, when I use regular HANDBRAKE settings to reencode the video from any lower resolution, it's always OK, so let's say I try a lossless MKV from a 1080p Blu-ray and wanted to reduce the filesize from 30 to 3 GB, no problem.

But if I get any lossless MKV from UHD/4K discs, and wanted to reduce the filesize from its current 50 GB to say, 3, 4 GB, and also change the resolution to 1080p, the end result from the video will not look the same as the 4K in my monitor (with HDR disabled) or even the 1080p disc.

Instead, I'll get all colors messed up.

Am I missing something crucial to configure while trying to reencode? The idea is to reduce any 4K source to 1080p and with that similar filesize.

HANDBRAKE's default settings (I also select SAME FPS AS SOURCE, and the video codec to H.265) aren't all it takes for the job?

[excellentswordfight]

If I am not mistaken, when I use regular HANDBRAKE settings to reencode the video from any lower resolution, it's always OK, so let's say I try a lossless MKV from a 1080p Blu-ray and wanted to reduce the filesize from 30 to 3 GB, no problem.

But if I get any lossless MKV from UHD/4K discs, and wanted to reduce the filesize from its current 50 GB to say, 3, 4 GB, and also change the resolution to 1080p, the end result from the video will not look the same as the 4K in my monitor (with HDR disabled) or even the 1080p disc.

Instead, I'll get all colors messed up.

Am I missing something crucial to configure while trying to reencode? The idea is to reduce any 4K source to 1080p and with that similar filesize.

HANDBRAKE's default settings (I also select SAME FPS AS SOURCE, and the video codec to H.265) aren't all it takes for the job?
I would guess that the source is HDR and that you are not handling that correctly, are your goal to convert it to SDR when you downscale, or do you wanna keep it?

[RanmaCanada]

Hadbrake can only handle HDR if you use the nightly builds.

[Ritsuka]

Not really, even HandBrake 1.5.1 can handle HDR10. Can you post the activity log?

[Perenista]

I would guess that the source is HDR and that you are not handling that correctly, are your goal to convert it to SDR when you downscale, or do you wanna keep it?If I wanted to convert to SDR which settings should I also use with it? Since the default ones result in fuzzy image...

[ShortKatz]

If you want to convert from HDR into SDR you need to go into filter settings and set the colorspace to BT.709. Which version of Handbrake do you use?
But anyway, the video should not look different regarding color, if you just change the resolution. Please check, if you also have this issue with the most recent development build (https://github.com/HandBrake/HandBrake-snapshots). Handbrake is very close to release version 1.6.0 and if this is a big (as well in the snapshot), it would be nice to have this fixed. If you think this might be a bug, it would be very helpful to report this here (it is important to include an encode log then): https://github.com/HandBrake/HandBrake/issues