LED light frequency and vision correction.

[HarryN]

[ QUOTE ]
Icebreak said:
HarryN -

Now I know how you build all those wonderful electronics. /ubbthreads/images/graemlins/wink.gif

____

That is supposed to be a secret Ice. /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif. Actually for my lights, I work with some other CPF'rs that actually have the experience and tools to build at the quality required. My own work is not good enough even for me.

 

[SemiMan]

There are a few things at play here. The lens of the eye is fairly simple in nature. It is a little better than a simple spherical lens, but certainly not aspheric. To that end, it can not focus all colors to the same spot. To that end, removing some of the colors could enhance focus. That of course, could mean either removing red, or removing blue, but generally, removing red will be better. However, do not confuse this with sunglasses that remove blue and suddenly make things much sharper. By removing blue from a scene, they are generally removing a lot of haze, etc. which tends to be on the blue end of the spectrum. Hence, it is like removing fog from the image. If you are wearing sun glasses, we can pretty much assume your eyes are already pretty closed up so you are getting maximum depth of field in your vision.

I don't know if it is accurate to say there is more red in regular daylight. Regular daylight is actually quite blue (5500K+), and on a hazy day can be much higher than this. So I wonder if your eye does focus on a particular color, or if it focuses on general brightness? .. any experts out there?

Given equivalent light, your IRIS does respond mainly to blue, and by closing your IRIS, you are going to get a signficant increase in depth of field, which is likely to be a far greater increase in apparent focus than from the ability to focus different colors.

Semiman

 

[cobb]

I wish I came across this sooner. My eyes in short are FUBAR. They suffer problems from MARFAN disease. The left eye has a dislocated lens and sees just light and dark. I can countfingers at a foot away. The left eye is around 20/400 with glasses, without them I can count fingers 10 feet away or so. Yes, you can not read the eye chart they resort to counting fingers.

Anyway I had a flash EGR test. They attack gold contact lenses to your eyes and forehead, put you in a globe and flash different color strobe lights at you and record the response. It determined I did not have RP, but something else. Since RP was ruled out, no one folloed it up. Of the colors blue I saw the best. I thought this was interesting as I love to stare at bug lights and the black light they used at Bush gardens to read the stamp on your hand.

I used halogen and CF lights to read by, but the flicker of CF lights bothers me, so i resorted to halogen. I heard a commercial for a white led light on the art bell show in 07 and ordered one. Although the light was rather dim, the bluish glow made print jump off the page at me. Maybe this is the focus thing you guys are referrring to? I bought a blinkmann head band and wore that light to read. Its the basic 3 white led 3 aa cell trek light that you twist on and off.

To date I buy led lights for a better reading light and some are dead on, some are disappointing. THe dorcey 3 aaa light was a disappointment as well as the cabelas 5 watt xpg, but the dorcey 1aaa light, bug outs 3w drop in, v2 6 chip and other cheap over drive 5mm lights are great.

Hope that helps. I wear glasses except for sleeping as they do make things a bit clearer. I believe my prescription is like a -18 and -21 dioptor, they are unable to measure a stigamatism.

I also discover from the folks at ccrane when I bought the light that they say others with RP and other retinal problems say it helps them. Likewise when I visited the rehab center for the blind.

 

[Icebreak]

SemiMan -

That's even more interesting than your first post. I wish I knew the answer to your question. Maybe an expert will chime in. Thank you for your knowledgeable contributions.

cobb -

[ QUOTE ]
cobb said:
Although the light was rather dim, the bluish glow made print jump off the page at me. Maybe this is the focus thing you guys are referrring to?

[/ QUOTE ]
Yes. I believe that's exactly what I experienced.

You probably know that white LEDs are actually blue LEDs with a yellowish phosphor membrane. When a white is over-driven sometimes you'll get a very cool or bluish beam.

I'll look around here and see if I have an appropriate keychain blue LED for you to experiment with. I think a blue 1W with a flood reflector would cause a greater effect but I know I don't have one of those. It may take a few days but in the meantime could you PM your mailing address so I can get it out to you when I find something?

--------------

- Jeff

 

[SemiMan]

Cobb, I have a custom made reading light I made out of Luxeon Whites I had lying around. It is great for reading, the text does literally jump off the page.

However, for more general usage, you can use flourescents and be happy with the results. I would suggest installing T8 flourescents with electronic ballasts. Electronics ballasts tend to have a lot less flicker than magnetic ballasts. They are also acoustically quieter, though the cheap ones put out a lot of electrical noise. Then make sure you go buy a high color temperature flourescent. They make daylight ones that are 6500K. The visual acuity difference between these and warm flourescents is astounding!

SemiMan

 

[jamaica]

[ QUOTE ]
SemiMan said:
There are a few things at play here. The lens of the eye is fairly simple in nature. It is a little better than a simple spherical lens, but certainly not aspheric. To that end, it can not focus all colors to the same spot. To that end, removing some of the colors could enhance focus. That of course, could mean either removing red, or removing blue, but generally, removing red will be better. However, do not confuse this with sunglasses that remove blue and suddenly make things much sharper. By removing blue from a scene, they are generally removing a lot of haze, etc. which tends to be on the blue end of the spectrum. Hence, it is like removing fog from the image. If you are wearing sun glasses, we can pretty much assume your eyes are already pretty closed up so you are getting maximum depth of field in your vision.

I don't know if it is accurate to say there is more red in regular daylight. Regular daylight is actually quite blue (5500K+), and on a hazy day can be much higher than this. So I wonder if your eye does focus on a particular color, or if it focuses on general brightness? .. any experts out there?

Given equivalent light, your IRIS does respond mainly to blue, and by closing your IRIS, you are going to get a signficant increase in depth of field, which is likely to be a far greater increase in apparent focus than from the ability to focus different colors.

Semiman

[/ QUOTE ]

Semiman,
The eye's lens is aspheric; I think you meant it isn't achromatic, which is true.

The eyes optics have a great deal of chromatic aberration, about a diopter and a half's worth or so. (I measured it a few years ago, but don't have the exact figures handy.) In fact, the eye relies on the differing focus between the colors in one of several servo loops maintaining optimum focus overall (by balancing red and blue defocus, green focus is optimized).

Briefly, the eye's optics have a longer focal length for red light, roughly neutral for green, and shorter focal length for blue.

Accordingly, a nearsighted (myopic) person's focus is improved by red light, and worsened by blue. Vice versa for farsighted (hyperopic) folks.

The effect is on the order of a diopter, as noted above.

Blue light, by the way, is damaging to the retina, in the same way as are other shorter wavelengths (e.g. ultraviolet). Cumulative exposure is a principal cause of decreased contrast and sensitivity (nightblindness) in elderly people. Ditto for cataracts, which are in large part a result of damage done to the eyes' crystalline lens by short wave light.

Cheers,
Jamaica

 

[cobb]

THanks icebreaker. I will give it a try. I know red does something for me, but it gives a headache after a few minutes. Like i said, if you know of a cheap resource online i wouldnt mind buying it. I know garrity use to sell a flat keyring light that was white, red or blue, but last time I was in walmart all they had was white. PM sent.

Of the led lights, I have rated them to help me read.

3 watt led BOG drop in
v2 6 chip
cabelas 5 watt xpg
vector mfg 3 led ccfl light
dorcy 1aaa light
stylus white led light
dorcy 1 watt light

The 3 watt led drop in I can read the phone book. Not much of a plot, but its a nice read with the naked eye and no bulky cctv equipment. The xpg and 1 watt are rather pale, than white or bluish. The vector mfg light is a but purple and does less for me.

SemiMan, Yeah, I think that would be nice, but I dont trust myself wiring it all up. I decided to give the cabelas extreme 6 watt light a try for reading as its turn key and seems to have a decent battery like unlike the cr123 lights. Cflights just dont have the effect LEDs do. YEah, my apartment has CF lights to help me see better than regular old bulbs, but I do wip out the led to find stuff dropped on the floor and reading.

 

[UnknownVT]

I have no doubts about what posters are observing -
but the conclusions may not be directly correlated.

Usually a normal eye has problems focussing blue light
(blue light is normally foccused in front of the retina).
Also Blue (shorter wavelength) light is scattered more in the atmosphere, and can cause visual blurriness.

From:
USAF Flight Surgeon's Guide: Chapter 8

QUOTE:
Claims have been made that certain lenses increase acuity--especially the yellow or amber lenses. This statement is usually based on the fact that light is scattered by haze or fog. It is known that the shorter wavelengths (i.e., blue and blue-green) are scattered more by haze and fog than the longer wavelengths (i.e., red, orange, and yellow). Also, the refractive characteristics of the eye causes blue light to focus in front of the retina and red light to focus behind the retina, when compared to yellow light that is focused on the retina. In other words, when the eye is emmetropic for yellow light, it is myopic for blue light and hyperopic for red light. This difference in color refraction, known as the chromatic interval, causes some distortion of the image on the retina. On theoretical grounds, then, the elimination of the short wavelengths by a filter should increase the sharpness of an image. This would seem to be confirmed by the use of yellow filters in photographing distant scenes. Such filters absorb the short wavelengths and allow the long ones to pass. They do give sharper photographs of distant scenes.
UNQUOTE


Note: although yellow seems to give acuity advantages - some of this may be psychological - as opposed to actually physical - although I'll swear yellow seems to increase contrast and definition for me......

QUOTE:
When worn, such yellow filters give a subjective sensation of increased brightness. This is a false impression, because the lens subtracts light, it does not add it. These yellow filters also give a subjective sensation of sharpening the image. However, all carefully controlled research experiments conducted to date (both civilian and military) fail to show a statistically significant increased ability to see in clear weather, haze, or fog, by marksmen and pilots using yellow filters. The difference between the effect on the eye and the effect on film is readily explained by the relative sensitivity to blue light of the photographic film on one hand and the retina of the eye on the other. Photographic film is extremely sensitive to blue light. Scattering of blue light, therefore, gives a marked haziness to pictures. On the other hand, the human eye has a very low sensitivity to blue light, so the scattering has less effect on ability to see in haze or fog. No ophthalmic filter exists which will appreciably increase the ability of the eye to see in haze or fog.
UNQUOTE

 

[Icebreak]

cobb -

Is that Cabelas light a lamp or a flashlight?

Also, padded envelope sent. Inova blue micro light with constant on. Cobalt blue just means it's a good color of blue.

UnknownVT -

Good information. Thank you very much.

I can't remember. Are you one of the CPFers that does some occassional subterranean urban exploring?

-------------

- Jeff

 

[UnknownVT]

[ QUOTE ]
Icebreak said: UnknownVT -
I can't remember. Are you one of the CPFers that does some occassional subterranean urban exploring?

[/ QUOTE ]
Nope, not me
although I think some people may have tried to bury me while I wasn't watching /ubbthreads/images/graemlins/grin.gif

Just some more thoughts on why blue light might help some see better - despite the fact blue is normally not focussed on but in front of the retina, also seems to scatter more in the atmosphere.

I think if one is hyperopic - ie: Far-sighted - normal light is focussed behind the retina - then blue light which would normally focus in front of the retina, may actually help correct far-sightedness by bringing the (blue) lit image focus further forward. Does that make some sense?

 

[Icebreak]

My apologies, Vincent. I think it was UndergroundVT I may have been thinking of.

[ QUOTE ]
UnknownVT said:
Just some more thoughts on why blue light might help some see better - despite the fact blue is normally not focussed on but in front of the retina, also seems to scatter more in the atmosphere.

I think if one is hyperopic - ie: Far-sighted - normal light is focussed behind the retina - then blue light which would normally focus in front of the retina, may actually help correct far-sightedness by bringing the (blue) lit image focus further forward. Does that make some sense?

[/ QUOTE ]

Yes, it does make since. It also lines up well with some of the other views/theories posted. Interesting stuff to me.

I took the 5W RB to an almost completely dark area last weekend. I've had it for a while but didn't realize the 30mm optic would throw the beam 100 yds in that environment. I was walking next to the river near the hydro plant and no one was around. I was enjoying my amazment of being able to see so clearly w/o glasses on. I could feel a presence in the area. Then I saw a pair of purple eyes staring back at me...then another and another and so on. Apparently there was a population of feral cats in the area. They were cautiously peeking out of their hidding places but not running away. Just staring. Some came closer. I could walk toward them and they wouldn't run. I turned on an incandecsent once and they scattered but stopped and returned to their curious observations after I turned it off. Odd to see twenty purple eyes shining back at you.

----------

- Jeff

 

[cobb]

Thanks Icebreak, I received the blue led light a few weeks ago. Lots of personal problems, been delayed getting back here.

Yes, the blue led was 100 times better than the bluish white one. I was reading labels off ingridents of stuff. It was a bit strange with it off adjusting to regular lighting. I am going to order a blue invoia x5 light. As for the future, I would want a white led light with a bulb bulb in it. The all blue would be too funny or strange for any length of time. I have a v2 6 chip, 1 red, rest white led bulbs. I wonder if they make a 1 blue and rest white? THat would be ideal.

The cabelas light are flashlights. Both the xpg and the extreme 6 watter.

THey scan some literature at work and email it to me and they have the invoices in excell printed in adobe, so I am set work wise. I just do it through the computer than actual paper work.

Firefox did allow or offer me to test their products, but i declined since I have my work environment working for me.

 

[Icebreak]

cobb -

Thanks for the letter and the Hamilton.

Ah. Very interesting. So you think a combination of one blue and two whites would work? That makes sense. I looked around a little for that combination to no avail. I'm wondering if a Modder would be willing to tweak your v2 6 chip to that configuration. It wouldn't hurt to ask, I suppose.

Anyway, thanks for reporting your findings. I guess we at least figured out a single blue would work as a label reader and that 1 blue + 2 whites might be of some help as a print reader. Cool.

--------------

- Jeff

 

[cobb]

Wonder if you can get an x5 with one blue and rest white?

 

[AndyTiedye]

Coast makes a light with 3 white LEDs and one each of red, blue, and green.
Each color has its own clickie, so they can be turned on in any combination.