Most modern LED headlamps, have a fixed focus beam. They generally have a tight beam in the center, with a nice useful spill beam around the central spot that makes up close work very doable.
LEDs in reflectors, will have much stronger spill beam compared to the incan in a reflector you are used to using. With LEDs, depending on the design of the reflector 40% or more of the light coming out the front can be in the spill light around the central beam (depending on reflector design), plenty for up close work, whereas on incans, often the amount of light in that spill beam is more like 25% or less.
You will probably find that almost any headlamp utilizing a MODERN (read, NOT a Luxeon) LED emitter will out-perform the headlamp that you have been issued... In fact, the low and medium modes on these modern LEDs will suffice for 75% or more of underground activities.
But, it's important that whatever you pick out, have enough runtime to last you through the day. Ideally, that means on 1 set of batteries, but if you think swapping batteries while down there isn't a problem then let us know as this is going to influence what options are on the table.
A few things to take into consideration:
1. Do not use a CR123 powered headlamp in a mine, as CR123s, while generally safe, have a higher chance of randomly exploding while being discharged than most other cell chemistries. And obviously, you need something rechargeable if you are going to be using it daily, CR123s are way too expensive to be using 8 hours a day...
2. Li-ion rechargeable should be considered fine, especially if you pick out a headlamp that comes with them pre-installed with charge controls and cell protection all built in.
3. Any multi-AA headlamp can be used with NIMH cells for recharge-ability. Since you will be using it every day, and want the investment to last, I would suggest Sanyo brand Eneloop NIMH cells. They are definitely some of the more reliable cells out there, and will deliver hundreds of useful cycles before they need to be replaced, some NIMH cells barely make it to 100 cycles before developing problems. Another huge factor is a good quality charger, as this will really maximize the performance and life you get from your rechargeable cells, do a little research, and check out chargers from MAHA, La Crosse, AmsMann, Accupower,... Something with individual channel control, and if possible, a capacity readout and cell testing capability, so you can always know that you are going in with GOOD cells that are ready for the day.
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On a side note, you should absolutely be holstering some sort of hand-held light as a backup. A 2xAA powered Fenix, or Olight, or something like that would probably not be a bad choice.
Eric
