Under Oregon law, when must you dim your high-beam headlights?

In Oregon, you must dim your high beams whenever you are within 500 feet of an oncoming vehicle or within 350 feet of a vehicle you are following. Avoid shining your high beams on any other occupied vehicle. If you dim your high beams before they can shine on other vehicles, those other drivers may extend you the same courtesy. [Using Lights, Hazardous Conditions, 7. Safe and Responsible Driving, Oregon Driver Manual]