# LED Flashlight Function

The scope of a light beam and power are two different things. Even if the power affects the scope, the beam concentration also plays a lot.

The range depends on the brightness measured at beam center (in one spot so) weighted by the ambient conditions (humidity, visibility, …).

This brightness is measured in lux and its measurement requires a light meter, an inexpensive device which can be obtained very easily.

The measured value is dependent on the distance. It is actually inversely proportional to the square of the distance, provided ideal conditions (no haze, …).

The formula relating the distance to the brightness in lux is the following, where D is the distance measurement, the L measured in lux, and indexes both measurement points, is valid only from a distance of a few meters:

It is therefore easy, from a single measurement at a certain distance, deducing that which one would at another distance, and the distance at which one would have a given brightness.

The ranges of flashlights provided on Garyflashlights are calculated from measurements conducted in lux at 10m and on the basis of 0.25 lux, which corresponds to the minimum illumination to see something with a minimum of detail.

Unfortunately, many websites are content to announce litters meters without any explanation of the method of measurement and calculation, and they do not hesitate to exaggerate to the extreme, sometimes up to indicate the distance at which the lamp can be seen instead of that at which it illuminates.

Even if these figures are really the result of a field test, they have no value without explanation because of the extreme subjectivity of visual assessment based primarily on the following:

The reflectivity of the subject matter: a dark forest, a light-colored ground, a sign …

Our night vision that can be big differences from one person to another our adaptation to night vision which is acquired in about 20 minutes, but can be instantly reduced to nothing by a light source such as a powerful lamp, the criteria chosen to determine the scope (see the target clearly, simply guess his presence ..)

So why litters in meters and no explanation of how they were obtained are nothing but commercial arguments often far removed from reality.
The only way to get an idea of ​​the actual scope is to find a measure lux done at a distance, and deduct itself that where it was 0.1, 0.25, 0.5 or 1 lux (depending on the value one chooses to take for reference).

The width of a beam is a rather vague concept, because a beam is usually broken down into two parts:

The central part (spot), very bright but narrow

The peripheral portion (spill), much less intense than the central portion but much wider.

Must therefore take into consideration the width of these two portions of the beam.

A narrow central part provides a concentrated brightness, so excellent range, but makes the unpleasant beam closely because he found both dazzling and illuminating a very small area. A narrow center portion is preferable to light far and wide to illuminate short or a more versatile overall use.

A wide peripheral part is very comfortable with the field of view it offers, by night hike, for example. But a wide beam sees its power “diluted” and therefore loses intensity faced with a narrower beam.

Finally, the transition between the two portions of the beam can be more or less gradual.

So there is no absolute rule on the beam width. Everyone must make his choice based on the intended use.

Incandescent bulbs have a particularly warm shade, pulling orange. The hue of the LEDs is generally much colder on the series of lamps, but they are the basis declined in a range of shades from coldest to hottest.

The color of each LED is indicated by a symbol consisting of two characters actually determining a tone range. This image map shows the main:

The most widespread on flashlights 1A is a pretty cool white.

Warmer shades can be more pleasant, less pale, but they can lose perceived power.

In addition to tint is to consider the color rendering index (CRI) . It reflects the richness of the light spectrum, ie the ability to faithfully reproduce all colors. Between 0 and 100, the colors will be even better than repaid this index is high.

While the DRI of an incandescent bulb is 100, like that of daylight.

Sodium lamps that are found in public lighting suffer from a particularly low IRC since it can be less than 15.

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