The JE Holden Camira uses a homofocal headlight reflector. From left to right: the high beam inner light, the homofocal combined high/low beam and the indicator.

Since vehicles have been driven at night there has been a need for effective illumination of the road ahead. Very early cars used lamps of polished brass and copper that contained a single candle. However, they could scarcely light the way of the man walking in front carrying the red flag!

This type of lamp was replaced with lamps burning oil and in some cases petrol, common until about 1910 when acetylene designs became popular.

Early Lamps

The acetylene lamp used two containers mounted one above the other. The lower one was filled with carbide in solid form; the upper one contained water which was dripped onto the carbide, with the flow regulated by a needle valve. The ensuing chemical reaction released acetylene gas which was transferred to the lamp itself through a tube. Here it burnt with a bright green flame. Some models of this type of lamp even had a primitive dipping function!

Variable foci reflectors can be optimised to produce whatever light distribution is required, with the entire reflector surface being employed. This type of reflector is used with a clear lens

The first electric headlights were powered by non-rechargeable batteries with quite limited life. The light output of these lamps was little better than oil or candle lamps, which meant they made little headway against acetylene lamps. Only the introduction of the generator saw the popularity of acetylene lamps begin to wane.

Early automotive electric lighting systems used a constant current dynamo complete with a magnetic cut-out which disconnected the dynamo from the battery when it rotated too slowly to charge. A typical battery of the time was described as a "12 volt 40 Actual Ampere Hour Accumulator". Headlights ranged in diameter from 12.7cm (5-inch) to 33cm (13-inch), with systems normally incorporating a switchboard complete with ammeter and voltmeter.

Some headlight clusters incorporate a variety of lamp designs. From left to right - indicator, parking light, projector style low beam, homofocal high beam.

Some lamps were even available with sealed, gas-filled reflectors plated in either silver or gold.

The brightness of these lights meant that a dipping system was needed. This generally took the form of moving the whole lamp body with systems using manual levers and even pneumatics to do this.

Electric switching of filaments to dip the beam was introduced in the 1930s. However, this was different to the present system – in the dipped position one headlamp was extinguished and the other mechanically dipped by means of a solenoid. Twin filament bulbs allowing the pure electrical dipping of lights were introduced in the 1940s.