Projector headlights — how they work and why they’re better

Projector headlights are more efficient because they focus light better than reflector headlights

Up until the 2000s, most cars and trucks used reflector headlights. In a reflector headlight, the reflector and bulb are matched to throw light in a certain beam pattern. The amount of light that hits the road is dependent on the type of bulb and the design of the reflector. The biggest complaint about reflector headlights was that they didn’t throw enough light on the road or throw it far enough down the road. That’s why carmakers started using projector headlights.

This headlight assembly for a Subaru Outback contains a projector style headlight for low beam operation and reflector style for the high beam

How they work

The light reflects forward from the elliptical cup/bowl reflector to the focal point midway between the back of the reflector and the condenser lens. A cutoff shield (shutter) is located directly below the focal point. It is closed in low beam mode to shield a portion of the light from the condenser lens.

The condenser lens

This type of lens excels at collecting divergent light rays and redirecting them into a straighter path. So it doesn’t really magnify the light as some “experts” claim as much as it collects and aims the available light.

They can be configured to produce both low and high beams

The diagram below shows how a single headlight with a cutoff shield shutter can produce both high and low beams.

Advantages of projector headlights

• They’re significantly brighter than reflector headlights.
• They’re less likely to blind other drivers because the light is directed down toward the road, avoiding casting glare into oncoming traffic.

Why you can’t retrofit LED bulbs into a projector headlight designed for halogen bulbs

You’ll see a LOT of “experts” pushing LED retrofits for factory halogen projector headlights. You should know that retrofitting a different bulb into either a reflector headlight or a projector headlight is not only illegal but will actually throw less light on the road and more glare into oncoming traffic.

• They’re not designed for LED technology.
• They trap heat. The life expectancy of LED bulbs is dramatically lowered when placed into a projector headlight designed for a halogen bulb.
• LEDs by their very design do not produce a 360-degree illumination like a halogen bulb filament. When retrofitted into a projector headlight, you’ll lose projection distance as compared to a halogen bulb in the same headlight.

©, 2021 Rick Muscoplat