Welcome and thank you for considering the SONY Communuty!
Regarding your concern about the backlight and a cloud of white light, this effect is actually working within the TV specifications. However, if you find this affects your enjoyment, here are a few adjustments that can be made to minimize this condition.
Reduce the Back light Level in the Picture Settings Menu.
Turn the Light Sensor setting to On in the Setup Menu.
Change the Power Saving setting to Low or High in the Setup Menu.
Set the Picture Mode to Standard in the Settings Menu.