Lumen is the unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle of one steradian from a uniform source of one candela.
The “brightness” we normally perceive should be called “illuminance”. Illuminance is the luminous flux per unit area of the surface of the illuminated object. The unit is Lux.
Lux = luminous flux / illuminated area.
With the above theoretical basis, we can now understand that because of different ways of light divergence, the camp lights and headlights with the same lumens can get very different brightness in actual practice.
The light of the camping lights spread evenly around them, suitable for close-range lighting and camp activities. On the other hand, the headlight produces a focused beam of light with a high illuminance in the focus area, and the non-focused area is almost abandoned.
So, the more focused headlights the better?
Not necessarily. The laser pen is very focused and strong, but only at that point; a powerful flashlight shoots very far but sacrifices most of the lighting area, so everything should be moderate.
A headlight that produces long-distance focused light beam is more suitable for high-speed sports or looking for roads. A light providing broad surrounding illumination is better for reading in the dark, camping, and saving battery. If you are looking for a headlight that works for a wider range of activities, or simply cannot decide which kind of light you want, a headlight with adjustable focus is your safest choice.
How to Choose Batteries?
Headlamps use all different kinds of batteries. How to know which one is the best for you? Let’s take a look at the pros and cons of different types of batteries first.
18650 Lithium Battery
- Capacity is generally between 1200 mAh ~ 3600 mAh
- Can be recharged up to 500 times
- Separated electrodes. A protective plate can be added to
prevent the battery from overcharging and over-discharging
- Generally 3.6V, 3.8V, and 4.2V
AA/AAA Batteries (Disposable)
- Not the most lightweight batteries
- Poor long-term shelf life
- Slightly more complex
- Very convenient to buy more when needed.
- Cheap option, if not recurring need to buy for long excursions
- Brighter and last longer than Rechargeable AA or AAA’s.
- No recharging needed – ready immediately
AA/AAA Batteries (Rechargeable)
- Environmental hazard
- Waste of Resources to buy and throw away
- Power not as strong as rechargeable 18650’s
- More economical option if you use headlamp often
- Environmental friendly
Built-in Rechargeable Batteries
- Not as easy to find as disposable batteries
- Not as powerful as disposable AA/AAA batteries
- Lightweight –built-in batteries are made for convenience and lightweight
- Economic option – no need to spend money on batteries
- Not reliable, if there is anything wrong with the batteries, the entire device is dead
But how do we know which type of battery is better in practice?
It is pretty clear that rechargeable 18650 batteries are a much better value for the average consumer. Lasting an average of two years with 500+
recharge cycles, they are the ultimate battery for use with flashlights. There is no reason to spend upwards of $5 on replacement batteries multiple times per week when you can simply buy a rechargeable battery.
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