Intuitively, a high-intensity, narrow-beam lights seem useful for the Search and Rescue (SAR) operations. But then again, intuitively, the narrow pencil-like beams may have impressive throws, but are they the best at visually finding things at a distance (and how narrow is too narrow)?
Given that many other similar questions have been studied if not by universities than perhaps by the US Coast Guard (or Army, or Navy, or Airforce, or somebody else), I have a feeling that the issue of what is the ideal light, colours, intensities, and beam patterns to assist in visual identification of ‘targets’ on water or in the air or elsewhere must have been studied as well. But I can’t find any data or papers or reports on it…
One light-related example that I know of is a plethora of studies on night vision and adaptation - a lot of it done by or for militaries, some pretty long time ago.
Would anybody know of such work on search beam characteristics?
I don’t know of a study, but I can chime in with personal experience of SAR operations on an inshore lifeboat.
The searchlights we had were much like a car headlight on high-beam, they were hand-held but plugged into the boat’s electrics so they were quite compact. For a person in the water you’re only talking about an object 30cm or so above the waterline, even with relatively little swell that’s hard to see from much of a distance when you’re only about two metres above it yourself, even in daylight, so a light that threw much further than the ones we had wouldn’t have been that helpful, especially if that came at the cost of a narrow beam.
For larger targets like small boats, they’d show up on radar, and if we had radio contact also on the direction finder, so most of finding them was done using instruments.
If we needed a lot of light over a wide area we had white para-flares.
What do you mean you can’t find the reports? Oh, you probably don’t have “secret” clearance.
There are way too many variables. The Navy is going to have a variety pack of different lights and equipment mounted and plenty of power for them. The Coast guard probably to a lesser degree.
What is the terrain , topography, weather, line of sight distance, plus other factors. Are you going to search for 10 minutes or 3 hours or all night?
If you’re talking about handheld stuff, there is no one or two or even three lights that are going to be best for all situations. If you can clearly define a lot of the parameters above then you might be able to narrow it down to two or three types.
I have no experience with SAR but a lot in night rabbit hunting (spotlighting/lamping). More experienced hunters frown upon using anything except the narrowest pencil beam possible saying anything floodier will “show the rabbit its way home”. The problem for me is, sweeping a spot around makes it easy to miss some or alert other rabbits as it takes time to sweep it. I have successfully used both spot and flood successfully.
A slightly wider spot such as that created by a large OP reflector or a high powered multi-led thrower is ideal for me. It reveals more while still having enough intensity to reach far. Pure flood is basically useless as it just dumps the light at your feet and a lot of it is wasted. Flood is ideal for close work or illuminating a larger area but not great for long range use. I personally would still prefer a pencil beam over a wide flooder.
If i had to search for people at night at long range, id choose a high powered multi led thrower with some spill. Like the blf gt94, wuben a1, convoy 3x21B, imalent sr32 etc.