Why is the PQ curve transfer used when playing SDR videos?

[Skelliger]

My configuration file is as follows:
vo=gpu-next
gpu-context=d3d11
gpu-api=d3d11
hwdec=d3d11va
hwdec-codecs=all
vd-lavc-threads=16
scale=ewa_lanczos4sharpest
cscale=ewa_lanczos4sharpest
dscale=mitchell
#hdr-peak-percentile=99.995
#hdr-contrast-recovery=0.30
video-output-levels=full
deband=yes
target-colorspace-hint=auto

This causes the shadow details to become blurred. I don't want to disable the HDR on my monitor. How to set up to use bt.1886 when playing SDR videos?

[eko5624]

[SDR]
profile-desc=SDR
profile-cond=get("video-params/primaries")=="bt.709"
target-peak=203

[kasper93]

Why is the PQ curve transfer used when playing SDR videos?

Because your display is receiving HDR signal.

I don't want to disable the HDR on my monitor.

In this case it is better to convert to PQ in mpv itself. As it does now. You can adjust target-peak and target-contrast to your liking. Currently it uses values reported by your display. It should look ok for SDR too.

This causes the shadow details to become blurred. How to set up to use bt.1886 when playing SDR videos?

Not sure what does it mean exactly. But if you keep your monitor in HDR mode, your GPU will send HDR signal to monitor anyway. You can force target-trc and target-prim in mpv, but this will likely produce worse/wrong result.