Beam distance is measured in meters and should not be neglected. This will measure the distance the light ejected from the flashlight will reach before it diminishes to the equivalent of the light that comes from a full moon, which is generally considered to be safe to travel in outdoors. Obviously, the distance varies depending on the setting. But depending on the location of your activity, distance may or may not be of great importance, so you should consider this before you make a purchase.
Candela refers to the intensity of a Lumen (ie, 1,000 lumens). It is similar to radiant intensity, the main difference being that instead of combining the contributions of each wavelength of light within the spectrum, it is weighed by the luminous function, which means it is measured by the human eye, essentially.
The ranges of lighting are an important factor to consider, and these range from 1 to over 700 Lumens. This will vary depending on the battery and bulb being used. It also comes down to the vision of the person using the torch. But any quality tactical flashlight will come with a brightness adjuster or multiple brightness levels. These usually come as one of either a head/tail twist, a body switch or a tail switch.
A lot of tactical flashlights have a simple on/off switch, which only gives you the option of one brightness level. These are generally the small flashlights, as they don’t have the capacity to encompass the necessary setting for brightness adjustments. If purchasing one of these, you should ensure that the level of Lumens are adequate enough for the activity you are undertaking.
More advanced or larger flashlights will have two settings: high and low. The lower setting will use less battery but omit a lower level of Lumens, resulting in reduced visibility. High settings will omit the maximum level of Lumens and use up much more of the battery life, and so you should save the higher setting until natural light has decreased dramatically.
Better tactical flashlights will have 3 or more settings from low to high. This gives you more variety when deciding on which is the best light to suit the moment and also which one will give best lighting while preserving the most amount of battery as possible. You can alter the lighting to the amount of natural light you have available in order to save battery.