We continue with the second and final part on guide to flashlights by Buddha. For those who missed the first part
The beam of light
The led emits light uniformly, so if you turn an led will have a clear light stretching in every direction but that runs a short distance.
To concentrate light and direct it as much as possible in one direction, using parables and the optics. Generally using parables, which according to their finish and size can determine different characteristics on beam of a single led. Making simplifications, plus the size of the parabola are large and more the beam is focused. The effect increases if the led size is smaller. The parables may have two finishes: smooth (smooth) which slightly increases the throw, or orange peel (orange peel) that removes imperfections but decreases the shot. For this missile torches have Spotlight much larger than others, and sometimes use small led although less efficient and powerful because they have a smaller surface emission and are easier to focus making the shot.
If the led power alone without any superstructure is measured in lumens, by introducing mechanisms such as parables and optics it is necessary to introduce another parameter, is the lux. The lux is the amount of light stronger than is in the beam of a flashlight, usually measured at 1 meter from the led. For example, a flashlight with a very wide beam might have a peak of a few thousand lux (5-7000), but if you concentrate the same light in a smaller area then these could increase up to 20 ‘ 000.The lux have nothing to do directly with the amount of light emitted. Extreme the concept a laser will have few lumens (in fact does not illuminate much) but many thousands of lux (because it focuses all light in a single point).
To better understand the effects of parables and lenses we watch a beamshot, that is a picture of the light beam from a flashlight defined on incredibleflashlight.com.
The beam is divided into 2 parts: the spot (center point) and spill (part which is around the spot). For those who want to throw flashlight, trying to concentrate more light as possible in the spot and make it as small as possible, at the expense of the brightness of the spill. To the contrary, until near worth the flashlight torches without diffuser that generate a beam bright spikes-free, very comfortable and restful in labor within striking distance of headlamp.