Hi. I have written some general information just because I have a lot of other things I should be doing and my addiction to lights is how I procrastinate. I am not so sure that my technical understand is 100% correct and therefore would like to ask that you comment on this. (in a nice way please)
Before we start please take note that I am in South Africa and shipping to US is crazy so don’t think I am here to sell. My on-line sore also does not accept international payments nor Paypal so don’t bother to ask.
Zoom lights vs Reflector lights
When buying a light, you might be curious as to what the benefits are for a zoom light vs a reflector light.
Firstly you need to understand how reflector based lights work: below is a illustration with two pictures showing the Extreme 1000 head lamp in action.
An LED has a beam angle of 120-180 Degrees. The hot spot that can be observed with most reflector type lights are the result of the outside of the LED beam pattern that is folded and directed by the reflector. There are some losses due to the imperfect reflection surface of the reflector, but it is minimal. In this example the red part is folded and redirect forward, where the middle section leaves the light unaffected. The shape of the reflector is very important. The majority are parabolic with the focused point on the LED. There are two ways to increase the hot spot of a reflector type light. The first is to make the reflector deeper, and the second is to make the reflector wider. In both cases more of the light emitted by the led is folded and directed forward.
The alternative to a reflect type light is the fixed accumulator lens which works on the same principle but also focuses the light with the optics.
The advantages of reflector type lights are that they make use of more of the available light as well as having a combination beam with both flood and focused areas. Interestingly this is also their disadvantage: The reflector type lights allows you to see both far and near but do not provide a uniform beam. This is ideal for cycling and search and rescue but not for trail running, map reading or working with your hands.
Zoom lens lights.
Depending on the design, the lens or the LED position can be adjusted to change the distance between the two. As the distance changes a different part of the beam emitted by the led is captured and deflected. Below shows two illustrations which depicts the light in focused mode or flood mode.
Focused/Zoomed mode:
When the distance is the greatest the lens catches only the light that is travelling directly at the lens. When the light enters the lens its angle is changed and then travels in a focused beam. As can be seen, most of the light is wasted when the light is in this mode, although the beam is more concentrated to some extent. The little amount of light are more directional and concentrated and therefore do not disperse as much, allowing you to see further. This is helped by the fact that there is little to none other light to over influence the eye.
The below illustration shows how the lens only captured the top part of the light emitted by the led. If it is assumed that the amount of light is uniform over the LED beam angle, which to some extend it is, then a significant amount of light is on the outside of the beam. just to illustrate we made a quick calculation based on area and in this example 86% of the light emitted would be wasted. This should in reality not be as dramatic because the spatial distribution is not uniform. It does show that a significant amount of light is wasted in zoomed mode.
Flood mode:
When the light is in the flood mode the distance between the lens and the LED is the smallest. Most of the light is captured which is composed of light at different angles. This results in an even beam.
Even with the lens being very close in most Zoom type lights there are still a significant amount of light that is not captured. The Extreme 1K is an exception. Its LED is moved up flush to the lens when in flood mode but some light still hits the outside adjusting ring.
The benefit of a zoom type light in flood mode is that the beam pattern is smooth and uniform. This is ideal for illuminating working areas, for example map reading or fixing something. Trail running is also benefited by this where lights is needed in near you without a distracting hot spot.
Summery
Both reflector and zoom lens lights have there benefits but one should be mindful of there disadvantages when considering your intended application. Sadly many believe that the zoom lens give you the best of both worlds where in actual fact it under performs in its focused mode. A fix reflector or fix lens makes much better use of the light it has but you can not change it if needed. It is possible to specify that the reflector and fix lens have a uniform beam in flood mode but very few buy such a light.