
First introduced in the early 1970's head torches are more popular than hand held torches for most outdoor activities, this is mainly because of the convenience of having your hands free and having the light automatically directed where you are looking.
Although some cavers still use acetylene powered lights most modern head torches use various configurations of battery power. The batteries can either be stored in the actual torch unit, which creates the lightest and most compact system or they can be housed in a pack on the back of the head, which is more balanced. Or the batteries can be kept in a remote battery pack. A remote battery pack is normally the heaviest and most bulky but it allows less weight to be on the head, you can keep the batteries warmer (increases their life in cold conditions) and you can use more or larger batteries, increasing the torches battery life. Which system is best for you will depend on your requirements.
The most important difference between modern head torches is the light source. The light source will be either a filament bulb or an LED (Light Emitting Diode) these two sources can then be divided further:
A filament bulb can be a standard filament bulb or a higher power Halogen (or other Nobel gas) bulb. The Halogen bulbs burn more brightly than standard bulbs and therefore give of a more powerful beam. They are however quite energy intensive and batteries will only last a fraction of the time of an LED powered torch. Any filament bulb torch will also need the bulb replacing quite regularly, as they will blow in the same way house light bulbs go.
LED's are categorised by their power output. Normally as either low powered LED's or high power LED's. The high power LED's are then given a wattage, this is at present between 1W and about 5W. Low power LED's are ideal for walking around campsites and other activities where you need a good "cloud" of light for about 15 meters. Higher-powered LED's are then used when the beam needs to be stronger and more focused.
Currently LED torches claim usable beam lengths to about 70 meters. LED torches give of a much whiter light than filament bulbs, they also are more efficient and batteries will typically last about 10 times longer than filament bulbs. The LED's they are also more durable and are quoted to last about 100,000 hours!
Probably the most versatile type of head torch on the market at the moment combines low and high power LED's. This allows the user to use the ultra efficient low power LED's for general use where long distance lighting is not required but still have the high power LED's when a greater range is needed.