A Candlepower Paradox

Ready to enter the Twilight Zone, filled with enigmas? Here's one for you.

Picture yourself (or rather, me...) in a typical wooded terrain in Georgia, or most any eastern US forest. Let's say you have with you something like a Surefire L2 (two levels of flood, one quite bright) and a pathetic little Inova X1 (a weak, long running spot with absolutely no spill whatsoever).

In the foreground, leaves on soil; from 45 feet (15 meters) in front of you onward there are tree branches to either side and overhanging a trail. In the distance, about 75 feet (25 meters) out is a stone bridge over a creek.

Without any added light you can just barely make out the presence of the bridge, but only as a vague, dim object whose form is fleshed out by your imagination. You shine the low-level flood light on the scene to illuminate the bridge and...it totally disappears. The trail, the ground, the tree branches are well-lit, but no bridge at all. So much foreground light that your pupils have immediately closed down to the point of extinguishing the dimly-lit bridge.

So you ramp up the lumens and hit it with the Surefire on high. Of course that will reveal the bridge. And guess what...everything around you is much brighter, but the bridge is still invisible. Totally gone. Everything in the depths of the woods plunged into total blackness.

Now you extinguish the beam and give your eyes only a brief time of 15 seconds to recover, and turn on the X1 with its dim spot, and you can now see enough of the bridge to make out some details.

My point is less pertinent to the desert, the plains, open fields, on water. But my point is, sometimes less is way more. Sometimes fewer lumens reveals more. Sometimes flood reveals less than spot. I walk in dark woods a lot, and find a dim light far more effective most (not quite all) of the time. What are your observations?

- Bill

Why am I whispering while reading your post :thinking:

CroMAGnet said:

Why am I whispering while reading your post :thinking:

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Maybe because it's the safest thing to do around people who just might be crazy???

CroMAGnet said:

Why am I whispering while reading your post :thinking:

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Now that's funny. . .I was doing the same.

Quiet!! weeahh hunting wabbits

CroMAGnet said:

Why am I whispering while reading your post :thinking:

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You might be whispering because woodfluter's post was very descriptive... almost like watching a suspenseful movie with someone and not wanting to talk real loud.

That is weird though, the Surefire L2 should have significantly more throw than the Inova X1. I do own an X1 and like it... but seing farther with it than an L2 is bizarre. Maybe the L2 is so bright that the light hitting the nearby trees reflected back at you making it hard to see the bridge while the X1 went perfectly straight towards the bridge?

iamerror said:

You might be whispering because woodfluter's post was very descriptive... almost like watching a suspenseful movie with someone and not wanting to talk real loud.

That is weird though, the Surefire L2 should have significantly more throw than the Inova X1. I do own an X1 and like it... but seing farther with it than an L2 is bizarre. Maybe the L2 is so bright that the light hitting the nearby trees reflected back at you making it hard to see the bridge while the X1 went perfectly straight towards the bridge?

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It does but it lights up the foreground and your eyes adjust to that brightness, so you can't see the bridge.
The same thing happens when you shine a bright light at something in the dark. You can see the something but what's (sneaking up on you from) outside the cone disappears.

i agree with iamerror about the L2 lighting up closer object and blinding yourself. another reason could be because the L2 uses a Lux5 which tends to be more of a flood light rather then for throw, but if you have a larger and deeper refector like the U2 or on a maglite you can get more throw with less flood. the X1 uses an optic which focuses the light into a spot with ZERO sidespill so you cant blind yourself with sidespill. maybe because of the tight focus of the X1 it seems like its out throwing the L2?
if you want to have better throw i would go with an incan instead. if it must be an LED then a Lux3 would be better. those are just my experience with the L2, U2 and X1. i'll have to borrow my GF's X1 to compare those 3 lights again. i'm sure you'll get more/better answers from other ppl that can explain it more clearly then i can, and make sence~

Too much spill kills your night vision. But spill is necessary to get that spooky Blair Witch thing going when you hold the flashlight under your chin. Not recommended to use a USL for that purpose, of course.

Maybe you can make an 'O' with your index finger and thumb to block out the sidespill of the L2 and see what happens. The light reflecting off of the leaves must have messed up your night vision.

OK, just in case I wasn't clear enough the first time...

Yes, the mechanism at work here is not really a mystery, it is absolutely evident, but still a paradox. We are used to the idea of more powerful lights, and those with higher lux ratings, having more throw. My point is that there is theoretical throw, and then there is real-life throw. And they aren't always the same thing at all. Because the way our eyes function get in the way.

More ambient brightness means your pupils close down. That effectively makes things that are dimly-lit seem to disappear. Ever notice how a shaded area on a brilliant sunlit day will seem totally dark, but closer to twilight (or with dark clouds overhead) the same spot will seem to acquire detail?

If nothing lies between you and your target, it will be illuminated more brightly by a light with more throw, better lux rating. And width of beam won't really matter.

If there is a lot of stuff nearby and the near distance, things like trees and light-colored fallen leaves on the ground, that part of the scenery will be illuminated very brightly. The brightness will fall off by the inverse square rule - or perhaps I should say the brightness of something twice as close will be 4 times greater! All that bright light makes the pupils contract, and the far lesser gain in brightness at the target (e.g. the stone bridge) is overwhelmed by the losses caused by contaction of the pupil. All because of the danged inverse square law.

More spill will aggravate the situation because it will light up more nearby scenery. But in the woods, even a moderate spot pattern can hit a lot of close-in stuff. The zero-spill dim spotlight misses all that scenery and contributes its bit of illumination to the bridge and little else along the way.

As I said, out in the open, with dark leafless ground, a different story. But in the open, on snow-covered ground, perhaps worse yet!

Anyway, I wanted to bring this up because I think we all can get hypnotized by numbers and forget that reality is sometimes very surprising.
- Bill

I wouldn't mind seeing a X1-ish light with a 1w or even 3w Luxeon. I disliked my X1 mostly because it was too dim. I liked the spot, and felt that it indeed had its particular uses, but it was just too dim.

In that regards, I think the Fenix L1P does a fine job. It has a fairly wide flood, but it's a dim flood. The hotspot is rather concentrated, although perhaps not quite as much as the X1.

And no matter how you look at it, the X1's switch sucks. Works fine for twist-on/off, but the momentary is finicky and useless at best.

It takes 30 minutes of darkness to fully regain your night vision. I limit my flashlight use in the woods at night unless I absoluely need a closer look at something

I just whipped out my Mag85 and lit everything within a football field and more up.

Hello Bill,

I think the problem is that you don't have enough power...

I have gone hiking in the forest with my U2 and noticed similar results. I just happened to have my X990 in the truck, and decided to take it for a walk to compare. The X990 lit everything up. My eyes completely lost they night vision, but I was able to see both near and far things very well.

With a dimmer light, you need to transform it into a spot light so you can only illuminate what you are looking at. This allows you to concentrate the light where you want it to go. However, for close in work, it is easier if you have a broad beam so you have a sense of perspective.

Since I don't want to carry the X990 on a hike through the woods, I approach this a little differently. I have gone to measuring the hot spot of the beams and found that (for me) a bright beam that is 12-18" in diameter at 2 yards works well in the near field. Add to this a variable brightness feature, and you can dial in the amount of light needed at the time. I find that 5 levels is usually adequate to find the right amount of light to match my night vision.

Of course, another approach to this is what Mag Lite uses. If you have a light with adjustable focus, you can use the tight focus for distance use and open the beam up for close in use. However, the beam quality can suffer if you open it up too much.

Interesting observations... I think everyone should take their lights for a walk in the woods to check their performance under a wide variety of conditions.

Tom

I mention this same effect (I often refer to it as the bounceback effect) in any number of my reviews and it's part of the reason I prefer the Night-Ops Gladius with it's tighter throw-oriented beam over the surefire U2 and L2 for most of my camping trips. I'm usually in the woods, or wooded areas with a lot of undergrowth and a flooder just lights reflects off all the leaves and such and leaves me light-dazzled. The spotters tend to punch through more and let me see what's beyond the immediate wall of growth.

I talk more about it here.

I guess, optimally, you should wear sunglasses while using bright lights. Keep those pupils open while lighting up the distant object better.

-LT

bfg9000 said:

Too much spill kills your night vision. But spill is necessary to get that spooky Blair Witch thing going when you hold the flashlight under your chin. Not recommended to use a USL for that purpose, of course.

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I absolutely agree with that first sentence... I think the ideal 'actual use in the dark outdoors light' would have a large but rahter dim hotspot with decent throw, and a wide but relatively dim spillbeam. From what I've read, this is pretty much exactly what Don had in mind when he designed his HD45. Specifically when used on low, of course... high should be plenty bright.

I've spent quite a but of time walking in the VERY dark outdoors on some very rugged rural property and, while it's comforting to have a brighter light available on my person, my two favorite lights for such use are the Infinity Ultra and a $.97 plastic 2xAA light I got from Walmart which uses PR base bulbs. I've put one of the Sino Union 5mm LED 'bulbs' in it. The reflector is faceted, and I've also sputtered it. There are other similar lights... the River Rock and other 0.5W lights, but I fear they too are a bit brighter than I find ideal.

This thread may be the one that convinces me to buy the RR 2C before Feb.27 rolls around. The only hole puncher I currently have is a 3D Mag with the Sears Craftsmann Worklight luxeon dropped in. And that light alteast has a little spill. And the RR would be suitable for camping and easy carrying, compared to a 3D Mag.

Nugget, I do mostly what you do - keep my lighting to a minimum most of the time so I can see and enjoy more.

Tom Silverfox, you are right too. Hit it with enough light and eventually, even though the source is close to you, your pupils have closed down about as much as they can, and then the illumination of distant things starts to catch up. Also agree about nicely variable intensity being one of the best solutions - walked dogs in woods last night with my new HDS EDC 60 for the first time, and that worked out very well all around.

And Zespectre, dead on about "bounceback" (interesting comparisons and tests there!) and using a narrow beam in situations like that.

Lunal Tic, I guess I need dark glasses that work the other way around from the inverse square - make bright things dimmer and dim things brighter. Hmm, sounds like optical equivalent of an audio compressor! I smell a patent application...

- Bill