Comparison Fenix BC25R vs Fenix BC21R V3.0

Luminous flux given out by a bicycle headlight (see "Type"); in models with adjustable brightness, usually, the maximum value is indicated.

The higher the luminous flux, the brighter the headlight and the greater the illumination range (see below). On the other hand, this characteristic significantly affects the dimensions, weight and cost of the flashlight, despite the fact that high brightness is not always required — for example, for episodic trips along well-lit city streets, a powerful flashlight is not needed. Therefore, it is worth choosing a bicycle headlight according to the luminous flux, taking into account the features of the planned application; specific recommendations for different cases (city, highway, rough terrain, etc.) can be found in special sources. Also, do not forget that the actual lighting efficiency depends not only on the brightness, but also on the shape of the light spot.

The greatest range at which a bicycle headlight (see "Type") provides effective illumination. The criteria for what is considered effective lighting are very arbitrary and may be different for different manufacturers; therefore this figure is approximate. Nevertheless, it allows you to fairly accurately assess the effectiveness of the flashlight and is more visual than the value of the luminous flux (see above). It is also worth choosing a bicycle headlight according to the range, taking into account the intended application; here note that in some (especially inexpensive) models, “range” can be achieved by narrowing the beam and, accordingly, reducing the light spot.

The longest time of continuous operation without replacing or recharging the power source, provided by a bicycle headlight (see "Type") in constant light mode (if there is a flashing mode, the operation time is usually longer, but it cannot be called the main one). This item indicates the value for the most economical format of operation, at minimum brightness; therefore, the actual headlight run time will generally be lower than advertised. It is also worth considering that many replaceable batteries (see "Power") are available in different capacities and have different durability — which means that battery life will also depend on the quality of the batteries. At the same time, this indicator is quite suitable for evaluating bicycle headlights and for comparing them with each other.

Bicycle headlight battery life at maximum brightness (see "Type"). This indicator is closer to reality than the maximum operating time (see above): in fact, it indicates the time that the flashlight is guaranteed to be able to work without replacing or recharging the battery. However note that some batteries (see "Power") can be produced in different capacities, and the manufacturer usually indicates the operating time for the most capacious (and expensive) batteries.

The main material used in the construction of the body of the bicycle light.

— Plastic. Inexpensive, easy to process, lightweight and at the same time very practical material. However the strength and reliability of plastic is noticeably lower than that of aluminium; however, in most cases, these characteristics are quite enough, the difference becomes noticeable only in extreme situations like bumps and falls (and even then there are also shock-resistant models made of plastic). This material is very popular in modern bicycle lights.

— Aluminium. Aluminium alloys with low weight have excellent strength and reliability, almost all bicycle lights made of this material are classified as shock-resistant (see below). The main disadvantage of aluminium compared to plastic is its higher cost, which is why it is used mainly in mid-range and high-end models.

— Rubber. The key features of rubber are softness and elasticity, which gives the flashlights made of it shockproof properties (even if impact protection is not directly stated in the characteristics). At the same time, for a number of reasons, this material is poorly suited for bicycle headlights (see "Type"), and it is used relatively rarely in flashing lights, mainly in inexpensive compact models.

— Metal. In this case, we mean metals and alloys that are not related to the aluminium described above, or whose composition is not specified by the manufacturer. Usually, such cases ar...e quite strong, however, the specific features of a particular metal (weight, fragility, corrosion resistance) can be different, and to assess the overall quality, it is easiest to focus on the price category of a bicycle light.

The presence of water protection can have an IP standard, which indicates the degree of protection against dust (first digit) and against moisture (second digit). Often the first digit may be omitted and changed to X (IPX6 instead of IP66), since water protection is the key parameter. Water protection is characterized by different numbers, where a larger value is considered more advanced. And the IPX7 models are completely capable of working under water for some time.

The presence of a mount that allows you to quickly remove the bike light and put it back. This can be either a mount on the body of the lamp itself, or a base that is constantly on the bicycle, to which the lamp is attached using a latch, magnet or other similar device. Anyway, the convenience of a quick-release mount is obvious: the flashlight can be removed (for example, to replace batteries, repair, or to avoid theft from a “tied” bike) in just a couple of seconds, and without the use of special tools.