This mode uses a single directional light located at the camera that always points in the same direction as the camera.
You can customize the Head Light properties in the File Options dialog box (Home tab > Project panel).
Click Home tab > Project panel > File Options .
In the File Options dialog box, click the Headlight tab.
Move the Ambient slider to adjust the brightness of the scene, and the Headlight slider to adjust the brightness of the directional light.
Click OK.