Q RE: Incan vs LED as personal searchlight

[Bertrik]

Well scientifically you don't need much evidence because it's already been widely accepted as the general theory (you can google it) that shorter wavelengths (higher frequency) have a higher probability of "bouncing" or "reflecting" off of something such as nitrogen and oxygen molecules in the atmosphere. How you apply that theory to anything else will surely follow the same logic. (A cloud is quite thick, which is why it casts a shadow onto the ground. It's not white because it "scatters" white light. Clouds are white because they reflect almost every spectra of ambient light, only absorbing a few colors.)

The atmosphere is much less dense than clouds, and a very small percentage of light "bounces" off of the molecules, and since shorter wavelengths of light (blue) have a higher probability of bouncing, the sky appears blue and the sun appears more yellowish. It's also the reason why the ocean appears blue. It's also the reason why when during sunset, the sky takes on more of a reddish color than mid-day since the light has to go through more and more atmosphere to reach you, reflecting more and more blue as it reaches your eye, appearing redder.

Anyway, the effect of this phenomenon on flashlights at close distances is very small, but still noticeable. LED's usually have a more pronounced "beam" that you can see in the air because the light gets reflected easier than incandescents.

I'm not doubting that the wavelength dependent reflection effect exists, but I doubt if it has significant effect with flashlights. The important parameter is the particle size to wavelength ratio. The sky is blue because of scattering on air molecules (much smaller than the light wavelength), clouds are white because of scattering on water droplets (much larger than the light wavelength).
My assumption is that outdoors reflection of flashlight light is dominated by reflection on tiny water droplets and that these droplets are similar in size to droplets in clouds (about 10 um). In that case, rayleigh scattering does *not apply* and all visible wavelengths scatter about equally.

 

[zipplet]

My own personal observation is that LEDs do backscatter more in fog than incans - you get a really nice 'lightsaber' effect from LEDs more so than incans. They don't throw as far in thick fog.

Try it - I'm sure you will be surprised - I was. Before I witnessed it myself I used to think that LEDs would throw just as far even in fog, but they don't...

Has anyone tried using a *red* LED light in fog? In theory it should throw quite well.

 

[mansell2]

Regarding the wave length and tint of LED vs INCAN. I have read about the effect of LED ligths and the biological design of our eyes (rod and cones) and now I am reading about the reflective effect. I am not an expert in understanding why LED is different than INCAN.

But has a searchlight I deffinately would choose a INCAN solution. IMHO and Incan added depth to what you are looking at. Searching rooms, closets, etc my LED make it look flat. Same thing in a parking lot.

I use my lights in Law Enforcement. The exceptions to my above statement is 1)Our Evidence technicians like LED for finger print hunting 2) I have searched the shallow area or a lake (6"-18") and I obersved that I prefered the LED over the incan. The incan seemed to cause objects to contrast better with the brownish lake bottom.

scott2907,

I have 2 additional recommendations as a fellow LEO.

1)We encounter a wide range of situations. Don't try to find the "One Light" that does everything. This will make you compromise aspects of the light.

2)Carry or have available a Incan AND LED light.

My current load out includes 3 lights
1)Primary - Mag 3C ROP LOLA with litho123 medium stipple reflector and 18650 Li-Ion.
2)Special Purpose - Mag 3C Mag85 (MAW85) with AW Incan Driver, fivemega 2" Deep reflector, and 3 x AW C li-IOn
3)Backup - LED Fenix P2D always on my belt.

Then I always have a Streamlight 20XP chargeing on my desk for those really long nights. I also have addtional 18650 cells for my ROP LOLA.

The one downside with my setup for some officer is charging. 1) Cost of Charging 2)Dangers of Li-IOn 3) no built in charging ports.

My 2 cents.

 

[mansell2]

I just re read your first post. If you choose incan for the small light.

Consider a rechargable solution for your SF. +1 to post #3. fivemega also makes a new body for the Streamlight Scopion so that it accepts a 18650 cell and a strion bulb. The price is also good in my oppionion.

 

[Blindasabat]

Good post Dinan. Thanks for the observation Zipplet.

its not "THE" Cree or "led" or whatever,
it is the current the led runs on.
I ve modded a 6P with a Cree P4 that runs on ~900-1000mA in a Cutlery Shoppe 19mm reflector and one does not notice a normal 6P light Assembly when this light is on.

I think the LED reflect-back is obscuring everything so you can't see how far the 6P is throwing. The Cree spill actually hurts you here. It's like turning on your high spill blue light in fog - all you see is fog. A red, orange, or amber light will do better. See below.

I don't believe the scatter theory without further supporting evidence. Clouds also scatter light and are perfectly white, not blue. From a theoretical point of view, cloud/fog droplets are still much larger than the wavelength of light, so I think the effect cannot be fully attributed to simple wavelength dependent scattering.
Other explanations for better throw of incans from earlier threads are: more uniform spatial distribution of light by incans (LEDs throw more light forward so it misses the reflector and therefore ends up as spill) and the stronger blinding effect of blueish light on the eye from LEDs opposed to the yellowish light from incans.

As you wish, but I and others have tested for this specifically, as zipplet attested to as well. I've seen it several times (I camp a lot) in different humidity conditions so I know humidity makes a visible difference. Why are ACTUAL "Fog" lights amber (not the dumb 'driving' lights people use today) and you see worse with your high beams on in dense fog? There is a lot of evidence. Test for yourself on a humid night. The farther away you are looking, the more scatter you see.
The uniform spatial distribution is true for overall throw, I may be wrong, but I think the discussion here was with LED lights that already have more throw than incans. With equal lumens, incans usually have more throw, but when a Cree drop-in makes 170L and the incan makes 65-70, I think the indoor measured throw (at 1 meter) is higher with the incan.

'The sky is blue' demonstrates the penetrating strength of red versus blue wavelengths of light. In the sky it is a combination of hitting molecules and water. In clouds, fog, and humid air it is the prism effect of moving from one medium to another - water to air. Look at a prism or rainbow - same effect, just exaggerated and more uniform. The color distribution is red orange green blue indigo violet. The red orange colors bend less, the blue indigo violet colors bend more. Clouds are just far more dense droplets, so they scatter everything. You can see nothing gets through - they are not clear. Scatter everything, you get white.

I'm a big LED fan, so I'm not trashing LEDs. I have FAR more LEDs than incans (like 40 LED lights to 3 incans (A2, SL Scorpion, and ROP). My G2 is currently running a 140L Cree BOG module. I just want more full spectrum LEDs. Until then, I will keep taking my A2 camping, but always use LEDs up close and indoors..

 

[Bertrik]

I'm not doubting your observations. I think there's more than just one reason why incandescents behave differently from LEDs and I don't like jumping to conclusions to pin it all on one specific phenomenon. I'd like to see a discussion about how strong the various effects really are (and if they are actually significant), but that is probably getting a bit too off-topic for this thread.

By the way, I found a nice website which has a program for download to calculate a couple of atmospheric phenomena that happen in light fog. It allows you to experiment with droplet size, light wavelength: http://www.atoptics.co.uk/droplets/light2.htm

 

[scott2907]

Thanks everyone for your suggestions and observations. After playing some more I find that I just can't put my finger on it but I find incans better at distance work and a more natural colour temperature to bring out detail. Mansell- thanks for your comments too. I do carry a small LED that I use for my paperwork in the car and in the dark. I tried this to search shallow water and you're right, it works better. I wonder if this is because its not as glare-y. Anyway, my LED head for my 6p is now being converted to fit a standard 3xAAA body that my force gives out with a pathetic "normal" LED x10 head. I'll not use that much. And the decision is to go with AWs 17670's and a LF EO-4. I'll report back on how that compares to my cree 3xAAA!

I might just buy myself a Fenix pocket rocket as well - just for the gadget value.

That lightsabre effect is definetly more pronounced with LED light. The more light that is visible to the side, the less there is to hit the target. I wonder if any of this has anything to do with the co-herency of the light. The diodes in a LED light are all lined up and spaced out after all. In an incan it "sprays" photons all over the place and they are less co-herent. Maybe that allows them to penetrate and light up a target better?

 

[FASTCAR]

LED all the way. Who wants while searching a light that dims rather fast and gets more yellow by the second.Not to mention bulbs to just fizzle.I remember dropping my 6p maybee 8 inches onto a table and the bulb blew.

 

[scott2907]

UPDATE: The 6p with EO-4 and 3.7v AW batteries doesn't appear to be as bright as my cr123x2 w/P60 (standard 6p) config. Don't know why. Although I will say that both LF and AW gave excellent service and good solid products. I'm a little disappointed with the resulting brightness and throw (no gain) but glad that I've got a recharagble 6p that I don't have to shell out for batteries on! I've still not achieved my goal of a great, small rechargable personal searchlight...

 

[jumpstat]

Z46+2x18650Leef+SW01+MN11 or LFEO-M3 is a good incan combo that is ideal for outdoor spotting. Quite decent runtime and output + the option of rechageables.