Version: 2017.3

QualitySettings.resolutionScalingFixedDPIFactor

Switch to Manual
public static float resolutionScalingFixedDPIFactor ;

Description

In resolution scaling mode, this factor is used to multiply with the target Fixed DPI specified to get the actual Fixed DPI to use for this quality setting.

using UnityEngine;
public class StartupExampleScript : MonoBehaviour
{
    void Start()
    {
        // Set the target Fixed DPI for this quality setting to be half of the default.
        QualitySettings.resolutionScalingFixedDPIFactor = 0.5f;
    }
}

See Also: Quality Settings.