The right light depends very much on the intended application. Key considerations include:
1. Level of light intensity sought (and brighter isn't always better; think of how lower brightness fog lights work better than regular beams or high beams. The same applies to low visibility settings and, in case the divers here were thinking about it, settings where the water seems clear, but there is a significant amount of partciulate matter in the water)
2. Size of the beam desired (size from a particular distance)
3. Need for a shadow-free beam
4. The color temperature desired (whiter light can sometimes be much more important than absolute brightness)
5. Accuracy of color when illuminated (different color temperatures reflect back color to look different, so if faithful color reproduction is critical, say in the case of evaluating a patient's skin color at an emergency site, this issue can be more important)
6. Need for a constant illumination level vs acceptance of progressive dimming (most lights lose 35% of their brightness after 15 minutes of continuous use and the brightness level only continues to decrease after that)
7. Burn time at a minimum level of illumination (most burn times reported by lighting companies are misrepresentations based on the fact that the filament is still glowing, even though the light level may no longer be usable for the intended application).
8. Acceptable bulb life and replacement bulb availability
9. Acceptable size and weight
10. Water resistance or, for diving, buoyancy in salt or fresh water.
11. Need for hands-free operation (including stability of beam and ability to fix beam in any given direction)
12. Field serviceability (i.e., if it breaks in the field, can you fix it with readily available tools or does it require manufacturer service)
13. Reliability (i.e., does it work first time, every time - you be amazed at the percentage of battery-powered lights that, fresh out of the box, don't work)
14. Durability of the casing (i.e., pass drop test, crush test)
15. Durability of bulb in a drop test
16. Ease of changing bulb
17. Ease of changing batteries in the dark
18. Polarity protection
19. Need for cold weather performance
20. Battery logistics (need to standardize on a single type of battery to be compatible with other applications; # of batteries you want to carry with you to sustain a light level; intention to fully drain batteries during a single application vs. expecting the batteries to be used over multiple sessions)
21. Total cost of operating (NOT purchase price, but the comparative cost of the unit itself plus the batteries needed to sustain the necessary illumination plus replacement bulb costs, totalled over a desired ownership period)
As Dennis Miller would say, I don't want to go off on a rant, but:
As, among other things, the manufacturer of high performance, professional battery-powered lighting devices (think search & rescue teams at the World Trade Center), I can tell you that the amount of poor performing, unreliable, and often dangerous junk palmed off on divers and non-divers is nothing short of disgraceful. But most of what is offered by some of these companies is remarkable hype and carefully crafted misrepresentations (e.g., one high-end, recognized name brand that says one of its top lights is rated to cast its beam 1000' based on the fact that the beam, when shot at a mirror 1000' away in total darkness, does reflect back. That's not usable light! In total darkness, a match can be seen for well over 1000 feet, so if all the light can do against that fake test is 1000', that's actually pretty poor!). And ignore the hype re LEDs bulbs - their efficiency is a fraction of a good Xenon bulb. And don't assume that lights with all sorts of fancy electronic components are automatically the best performers - some voltage regulation strategies can incredibly improve performance, others are so poor as to be laughable!)
Since I'm "in the business," I'll forego the opportunity to slam any particular manufacturers by name and rather suggest that if you identify the issues from above that are important to you and then seriously evaluate the crowded field of potential models, you may find that your field of reasonable selections becomes rather limited.
And again, as Dennis Miller would say, "but that's just my opinion."
(Ratso- since, as a non-diver, you were so bold as to venture into this forum, PM me re your needs and I'll be glad to identify options for you).
