I'm sure this question has been posed before but... I need a spotlight to shine from my truck occasionally when coming home from work. I live in rural Indiana and drive on many country roads. I need a light that can shine a long way across plowed fields. Any suggestions on candle watt power? Or is CWP just a marketing gimmick? Should I be looking at lumens? I was unaware of how in depth the world of flashlights/spotlights was. Any suggestions are greatly appreciated.
Maximum possible candle watt power
- Thread starter mattf765
- Start date
FRITZHID
Flashlight Enthusiast
well, how far out in the field do you need to see? once you reach a certain point, the light may reach but your vision can't make out whats lit up anyway.
Matt, give us an approx distance you need to cover. Is it 500 Yds, 750 Yds? And what objects do you want to be able to see at that distance? And yes, claimed candlepower is just that, a wildly inflated number. The typical 10,000,000 MCP light is actually about 300,000 to 500,000 if you're lucky. Lumens produced and how it is focused (floor or throw) is a better way to figure out what you might need.
Yep, however there are a few corded spots that are rated pretty honestly:
Lightforce, the SL 240 is rated at 1mil I think. It can throw light farther than you can see and is overkill in most situations for us. We prefer the SL 170.
Collins Dynamics or Havis. I used the CD-Magnums and CD-12's for years but they are pretty heavy and expensive.
Both of these will out-throw just about any "10 million candlepower" incan spotlight.
Throwing a SL240 out over someone elses field will certainly attract attention.
lamp with
1000000 candles luminous intensity
illuminates a spot with
1 lux ,E (full moon overhead in the tropics)
How far away is it?
R=sqrt(I/E)
1000 =calc'd distance in meters, R
Most of the land I would be shining a light in is my own land. And no I'm not "spotlighting." I do hunt but I'm just curious as to the wildlife in my fields. I'm talking at the farthest 750 yards. Would like something durable enough to leave in the truck year round in all weather conditions.
JacobJones
Enlightened
Hmmm, 750 is quite a long way. Do you have a budget???
~0.5 million cp.
You know the spot diameter you need? A 40' diameter [1 degree beam angle] is probably ambitious.
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I suppose 750 yards is a bit ambitious, especially at night. More like 3-400 yards at most. Budget is not really an issue so much as durability and dependability. Don't know much about beam angles but I assume spot diameter is diameter of the light at a given distance? Max distance? I suppose I'd like to have a wider diameter than narrower.
lamp illuminates a spot with
1 lux, E
at
300 meters, R
or
328 yards
with candlepower, I, is E(R^2)
takes
90000 cp
a spot
100 feet in diameter, SPOTDIAM
at distance
1000 feet, RANGE
gives a beam angle, BA, of
2xARCTAN(SPOTDIAM/2xRANGE)
5.724810452 degrees
And thank you to Mr. Combs for suggesting a second look at what seemed to be simple geometry.
1 lux, E
at
300 meters, R
or
328 yards
with candlepower, I, is E(R^2)
takes
90000 cp
a spot
100 feet in diameter, SPOTDIAM
at distance
1000 feet, RANGE
gives a beam angle, BA, of
2xARCTAN(SPOTDIAM/2xRANGE)
5.724810452 degrees
And thank you to Mr. Combs for suggesting a second look at what seemed to be simple geometry.
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R = sqrt(I/E)
R^2 = I/E
I = E(R^2)
E = I/(R^2) = 1000000/(458^2)= 4.8 lux.
Since the 1 million is probably only known to one significant figure this final result should be reported as 5 lux. The 458 is known to three significant figures but the final answer is limited by the number that is the least precisely known.
