Cavers - "White LED's Suck..."

[PeLu]

OK, next try to post the mesage

I ran across this discussion...Comments?

Ok, I wrote a lengthy comment and hit a key which deleted everything accidently .-(

Anyway (short as I have no time now):

I wrote probably hundreds of pages on cave lighting (in different languages).

Some of the points mentioned in this paper are not as silly as they look at the first glance, but I agree that it is somewhat outdated.

When you use incandescents with a regulated source (like Ocelot's Willie Hunt LVR) they came close to LEDs.
And LEDs were overrated for a long time.

And, as mentioned before, LEDs have the possibility of using them at lower levels efficiently.

The author also compares electric lights only with carbide caplamps, not with the CB (ceiling burner) type which is quite common around here.
These CBs light up the whole surrounding of the wearer and therefore everybody illuminates for everybody. You get a much better impression of the cave passages and rooms and the person who makes the scetching has much better results.
On the other hand, more or less focused lights (mostly electric) are what I call egoistic. They just throw a cone of light in the direction the wearer is looking (more or less). You get a completely different view of the same cave. Difference in between this light categories is less in smaller passages, of course. And vice versa.
A CB can put out easily 500lm and in our case carbide is easily obtainable and more or less free. And a well maintained lamp works quite well, but never as easy as an electric one (with exceptions).
I now use a Melzer Radon which tries to copy the CB effect with an LED. It is quite nice and comes close, but not perfect (in that way). It lights up half the angle of a free flame.
some 6 years ago I wanted to buy a NevTec lamp as it came close to a carbide light's unfocused beam.
At least as good were DougS' caving lights.
I also prefer to have a seperate spot to look down pitches (most of our pitches are less that 1200 ft deep .-)

Light colour: It depends higly on what you look at. Ice (quite common around here) lights up well with white LEDs. Brownish rock (like quite common in TAG and Indiana/Kentucky) better with carbide lights. Our cave walls are usually almost white and work well with all kinds of lights. I had cases were people with carbide or incadescent lights could spot red survey marks much easier that I could with a LED light. On the other hand I found a rusty spanner with my quite dim LED light (back in 1999) where carbide cavers looked around without success. Both light colours have benfits and shortcomings. Mineral collectors prefer the white LEDs.

As I wrote yesterday, I would like to try a StenLite with one white and one amber or orange LED. Both with the widest beam available.

Fluorescent lights: Smaller tubes have lower efficiency, you need a converter which is usually a little bit less efficent as one used for LEDs. Fluorescent drop in efficiency at lower temps, LEDs increase. Caves are usually relatively cold (around 0-5°C here).
And tubes are fragiile compared with small incandescents and LEDs.

If the author of this pamphlet states that he and others missed a passage due to their lightig it says more about their caving skills than about the lights .-)
Alpine caves tend to be more confusing than most of the US ones (as the bedding planes are never horizontal) and I cannot remember ever missing a junction due to bad light (but I may have forgotten it). I used to cave with a 3.7V 0.07 A bulb and a square battery (some 50 hours of light). This was a backup, of course, but got used sometimes for a longer time.

much more to write about...

 

[dar]

David Campen:

How about the UK4AA eLED? =)

http://www.uwkinetics.com/I_4AAeLED.htm

This is a great light for the cave pack.

Oh yeah, and this article is crap.

 

[David_Campen]

David Campen:

How about the UK4AA eLED? =)

Yes, I like these, I carry one in my cave pack as a backup light but it is a 1-watt LED and doesn't have anywhere near the throw of the UK4AA/4-watt incandescent that I carry in the pocket of my cave suit.

 

[jashhash]

Ok so LEDs may be more reliable in an underground expedition where you realy dont want to burn out a bulb but if you think about our position as CPF members objectively you will see that we have a huge bias in favor of LED lights. After all LED's are the new cutting edge of flashlight design and to learn of thier shortcomings would cause many of us to deny rather than to take an objective look at the facts.

One of the main arguments in this pamphlet is that of full spectrum lighting. According to the author LEDs emit light highly in the blue and yellow spectrum but have gaps in it's spectrum which means certain colors will not be easily diferentiated under LED lighting.

There is an easy way to test the difference in color rendition between filament and LED lighting. If you were to create a collor pallet of colors of different wavelengths and make the colors almost imperceptively different in color then you could take turns shining LED and Filament lighting on the pallet. If his research is true, then it should be much more difficult telling the difference in colors of 700-800 nm under LED lighting.

Im gona make a color pallet of several different swatches of red (700-800nm) and see if his findings are true.

 

[jashhash]

The experiment:

Well I havent made color swatches yet but i have noticed a visible difference between two colors in particular. Blue and red. In this experiment I compared the color rendition properties of a Nuwai Q3 and Mag 3C by shining it on various colored surfaces. The difference is rather striking.

Results:
When the LED is shined on a red surface the resulting color looks more brownish in comparison to the Mag 3C. When shined on a blue surface the resulting color looks much more vibrant when compared to the Mag 3C.

These results seem to affirm the author's research regarding the LED spectrum. Because of these results I am beginning to think the best way of making a LED light that can diferentiate color is by combining red, green, and blue LEDs which may not appear to be pure white but perhaps it would be better suited for color rendition.

Further research suggests that Incandescent lighting has its shortcomings too. While LED lights emit little light in the red spectrum incandescent lights lack the blue spectrum.

Another important factor in determining the most suitable light wavelength is how we percieve light. I would assume that humans are most comfortable with light which is close to the suns natural spectrum. So perhaps the goal of a flashlight should be to mimic the sun's spectrum.

Incandescent left, Fluorescent right.

The colors of natural sunlight

 

[Dr_Joe]

Color perception is in part a learned "brain" skill. That is to say that your brain has developed it's pattern recognition sets for color from what your retinas have been telling it since you exited the womb. The other "part" of the equation is the force of evolution that created your retina and brain had the sun as it's only light source for millions of years.


Since the gross majority of color recognition information was from the reflection of sunlight, then your brain will identify color patterns when the reflections are from a source of similar color spectrum to the sun (ideally the sun itself) more easily than with any other spectrum.

That is not to say that your brain stopped learning a minute after you exited the womb, in fact it has an amazing capacity to adjust to new inputs, even "rewiring" itself with new axonal connections if necessary to overcome a defecit.

Translation; your brain would much rather you bring the sun (or it's closest facsimile) down into the cave with you, but if a candle is all you've got, your brain can eventually be beaten into submission

If you ONLY had a blue light, for example, eventually your brain and your eye would compensate with new connections and new cells on your retina to make up for the deficiencies in color rendering, but you would have to be immersed in that color spectrum for 2 weeks for that to happen. (less than practical in the real world) You could always wear blue glasses for 24/7 for two weeks prior to caving to force your retina and brain to adjust ! (quite a fashion statement if nothing else )

That said, the obvious downfalls to any partial spectrum light (red, blue, etc....) will be their inability to reflect some portion of the spectrum completely. Carry that "extreme" back a step to a light that for the most part is "white" (imitating full spectrum but not actually full spectrum.......... like ALL man made light sources, incan, led, HID, flourescent, combustion, etc.......) and you will have some "deficiencies" reflecting certain parts of the color spectrum. It's inevitable, until you harness a little hydrogen fusion light source like the sun. Translation: every light is a compromise in color rendering, however some are a bigger compromise than others !

This is one of the reasons I've always loved the SureFire A2. It runs a regulated (LVR) incan (outstanding color rendering) plus 3 led's. Together the color rendering is unmatched !)



PeLu's comments and experience, and Jashhash's observations are both fascinating and intriguing ! :goodjob: Great thread !!

 

[jtr1962]

Further research suggests that Incandescent lighting has its shortcomings too. While LED lights emit little light in the red spectrum incandescent lights lack the blue spectrum.

Yes, I discovered that years ago, and that's why I've used fluorescent for all my interior lighting for the last 20+ years. Most of my decor tends to be in blue and green family, with white also. As you saw, blues tend to look purple under incandescent. Plants look a sickly yellow green, and white never really looks, well, white. I admit that until installing full spectrum fluorescents in the last few years I did have to put up with the shortcomings of fluorescent, namely the deficiencies in the red part of the spectrum. This didn't matter too much since most of the colors I use tend to be from the cool part of the spectrum. Therefore, even under cheap cool whites my rooms looked much more like they would under sunlight than they would have with incandescents. Full spectrum fluorescents more or less solves the red problem as well. I'll also add that neutrals like grays also look better under fluorescent than under incandescent which tends to make them look yellowish. I also find I get headaches under any light too different from sunlight in color temperature because of my brain trying to auto color balance. Being under incandescent for a while actually gives me terrible headaches.

There is no perfect manmade light source-yet. I think white LEDs combined with red to fill in the gaps in the spectrum might come close. Ultimately I'm quite sure we will have LEDs with better color rendering but which also maintain a color temperature similar to sunlight.

 

[David_Campen]

If you ONLY had a blue light, for example, eventually your brain and your eye would compensate with new connections and new cells on your retina to make up for the deficiencies in color rendering, but you would have to be immersed in that color spectrum for 2 weeks for that to happen. (less than practical in the real world) You could always wear blue glasses for 24/7 for two weeks prior to caving to force your retina and brain to adjust !

Excuse me, where did you come up with this? I believe that that is false. If you use a monochromatic light source you will not be able to discern colors - no matter how long you take to allow your brain and eye to compensate.

 

[jashhash]

I think what he means is that your brain will get used to seeing everything blue and not that you will be able to distinguish colors under a blue light.

If you look at the LED wavelength table in the pamphlet you will see that the red spectrum is not the only color lacking. There is also a lack of deep violet and cyan. Do you suppose it would be possible to make an LED which has dies of multiple wavelength? Maybe you could section off the LED in such a way as to create 6 distinct wave lengths of color which would blend together and improve color rendition.

 

[David_Campen]

If you look at the LED wavelength table in the pamphlet you will see that the red spectrum is not the only color lacking. There is also a lack of deep violet and cyan. Do you suppose it would be possible to make an LED which has dies of multiple wavelength? Maybe you could section off the LED in such a way as to create 6 distinct wave lengths of color which would blend together and improve color rendition.

They are continually improving. The White Luxeons aren't bad and the Warm White are even better.

http://www.luxeonstar.com/item.php?id=393&link_str=208&partno=LXHL-NWG8

 

[Ken_McE]

Multiple Wavelength Dies

Do you suppose it would be possible to make an LED which has dies of multiple wavelength? Maybe you could section off the LED in such a way as to create 6 distinct wave lengths of color which would blend together and improve color rendition.

They have three color leds available up to one watt now. They all use RGB because these correspond to the three color sensing cones humans use. We see the other colors as combinations of RGB. By changing the brightness of the dies independently you can generate light in almost any color. However if you want those deep purples you would have to add a near UV die to the mix.

 

[Dr_Joe]

Excuse me, where did you come up with this? I believe that that is false. If you use a monochromatic light source you will not be able to discern colors - no matter how long you take to allow your brain and eye to compensate.

David,
The science of the brain and the special sense organs like the eye is very complicated, and would require years of study to even begin to comprehend. Thankfully, at one point in my career I got paid to do just that

(experimental neurophysiology department director)

If you want to learn more, start with the link below, it's a good primer and very informative. If you would like direction to more informative texts let me know.

http://www.du.edu/~jcalvert/optics/colour.htm

 

[PeLu]

Color perception is in part a learned "brain" skill....
.....for example, eventually your brain and your eye would compensate with new connections and new cells on your retina to make up for the deficiencies in color rendering, but you would have to be immersed in that color spectrum for 2 weeks for that to happen. (less than practical in the real world) You could always wear blue glasses for 24/7 for two weeks prior to caving....

On the other hand, when staying in a cave for maybe a week and using almsot exclusively carbide lights, the sunlight looks very 'unnatural' afterwards. Not cosy, warm and soft. No, it is blue, cold and alien. For a short moment. Coming out at night with somewhat full moon is even more dramatic.

And one wrong assumption in the quoted pamphlet is, that white LEDs are bluish and this is unchangeable. As we all know, there are different light colours available and I know several caving lights which just add amber or even red LEDs.
But most caving light designers head for the highest efficiency and take the colder light colours.

 

[jashhash]

It seems that OSRAM has taken up the challeng with thier high flux RGB LED which they claim can put out 120 lumens at a 40 lm/watt efficiency. These numbers seem a bit exagerated so realisticaly only time will reveal if thier boasting is true.

http://www.osram-os.com/news/news-MultiLED.php?lan=eng&id=93

 

[Dr_Joe]

David, take note regarding retinal and brain color perception adjustments:

........when staying in a cave for maybe a week and using almsot exclusively carbide lights, the sunlight looks very 'unnatural' afterwards. Not cosy, warm and soft. No, it is blue, cold and alien. For a short moment. Coming out at night with somewhat full moon is even more dramatic.
QUOTE]
See, I told you your brain could be beaten into submission ! (and it only took a week) :devil:

 

[David_Campen]

If you want to learn more, start with the link below, it's a good primer and very informative. If you would like direction to more informative texts let me know.

Thank you but I already seem to know much more than you.

Thankfully, at one point in my career I got paid to do just that (experimental neurophysiology department director)

In your profile you claim to be an ER Doc, now you are claiming to have a PhD in neurophysiology?

You may be an physician - physicians are very highly skilled technicians who often actually understand very little, but I sincerely doubt that you have a PhD in neurophysiology.

And, I stand by my statement that when using a monochromatic light source you will have _no_ color vision - no matter how much time you give your eyes and brain to adapt.

 

[VidPro]

there are no caves like Jtice (awesome) to go around here, without guides, and guides means $$$
but walking about in the dark, my RGB light set on White, Sure brings out a much better range of colorations.
can't see where it would help anything in a grey cave, but a colored one it would be a real advantage.
i would think that a rgb blended led source (with mabey that added uv) would be MUCH better than incadescent. and better than what we call white , in leds, which are really just bluish yelowish things comparably.

plus there is a big difference in incadescents, depending on the light, and the bulb , some burn lots hotter, and therfore much less yellow.

 

[jashhash]

David and Joe... Please cool it and keep this thread civil. If you wana do some b*tching then use the PM feature.

The prob with that OSRAM LED is the DIE size is much too big for focusing a beam. I think our best alternative right now is to use a tri lux with red, blue, and green Luxeon III's.

If you want to do some serious cave exploring then you may have to invest in GPS reciever (or borrow one). The cheapest units cost around $50. You can find the GPS coordinates of uncharted caves in your location by doing some research online. Might I suggest going to www.Geocaching.com. Often people will hide cache containers in, or around the entrance of caves. Doing a caves search reveals 515 results when putting in the word "cave" into the key word search feature. Using this I have recieved information of multiple caves (including the origional bat cave from batman) within 50 miles of where I live...

 

[PeLu]

Re: Cavers - "White LEDs Suck..."

And, I stand by my statement that when using a monochromatic light source you will have _no_ color vision - no matter how much time you give your eyes and brain to adapt.

I can only report a real case:

I caver from Holland working at Phillips (not shure if it is OK to tell the name) as a developer for LED applications had access to very early Luxeons (as they were made there).
He used an amber (yellow) one, as they had more than twice the efficiency than the white ones (and were available sooner).
It turned out that it worked much better than expected and he got used to the colour and everything looked 'natural' .
Of course there will be objects which are less visible due to their colour. As I reported above with the spanner/wrench and the survey marks.

He made very difficult trips, several days long. I could look for the emails for details.

And, Dr. Joe, as all cavers know, it does not need a week, even after a normal trip (10-12 hours), coming out at night, everything is very bluish. Or, more correct, had been a decade ago.
After a week in a cave, you probably have a combination of psychological and physiological effects.
But I'm a layman there and only can report experiences.

 

[jashhash]

I assume the amber luxeon was not purely a monochromatic source of light. The Amber luxeon probably covered a good array of wave lengths from 525 - 675 nm. This variation of wave lengths would still allow some color rendition. I would assume that a purely monochromatic light source of a specific wave length would not allow for any color rendition even if your mind has the ability to grow accustom to its awkward light. I assume that any variation in reflected wave lengths would allow the mind to adapt to it and the mind may re-wire itself in such a way to fill in missing colors. Im not so sure if this is possible with a purely monochromatic source or not though.