State of Decay 2: Juggernaut Edition - HDR Settings

The peak brightness in the game seems to be fixed and not adjustable. This game does not seem to use the Xbox HDR system calibration settings. 

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The peak brightness limit is about 1430 nits. If your TV's peak brightness is anything other than 1430 nits, then use your TV's Tone Mapping modes. 

If your TV's gamma settings are set correctly, it is recommended that you leave the gamma slider in the middle position.