Rick's Free Auto Repair Advice

Projector headlights

Projector headlight — how does it work, why is it better?

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 far enough down the road. That’s why carmakers started using projector headlights, so throw more light onto the road and throw it farther down the road.

projector headlight versus reflector headlight

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

How a Projector Headlight works

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.

Low beam projector headlights and high and low beam projector headlights

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

how a projector headlight works

Advantages or 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.

Retrofitting LEDs 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.

  • Projectors were not designed for LED technology.
  • Projector headlights 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 project headlight, you’ll lose projection distance as compared to a halogen bulb in the same headlight..


Posted on by Rick Muscoplat

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