I have a led flashlight (Arc-AAA, 5.5 Lumens) and my child plays often with it. I know, LEDs are not harmful to the eyes. But can it be harmful if one looks directly into it? How bright can be a flashlight, so one can look directly into it without damaging the eyes?
Is LED harmful to the eyes (if one looks directly into it)?
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Jarl
Flashlight Enthusiast
lol... how bright can it be.... It's impossible to say "9739 lux is safe, but 9740 lux will damage your eyes" or similar (completely made up). TBH, give your child a decent light and they'll quickly learn not to shine it at their face 
IMO it's fair to say that a single exposure to current single die LED's isn't going to harm your eyes. However, with the more powerful lights, such as the P7 dies and some incans, you probably can cause damage over time, just as you can by staring at the sun. 5mm LED's causing damage? No.
IMO it's fair to say that a single exposure to current single die LED's isn't going to harm your eyes. However, with the more powerful lights, such as the P7 dies and some incans, you probably can cause damage over time, just as you can by staring at the sun. 5mm LED's causing damage? No.
Yapo
Enlightened
Its the Utra violet and maybe Infra-red? that damages your eyes when staring at the sun...thats why they invented sunnies and warning labels on lasers i dont think 5 lumens of visible light from an LED would cause any permanent damage to your eyes
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AvidHiker
Enlightened
I agree, a small 5mm LED should not be a problem for a child's eyes (IMO, but I'm not a doctor). The latest high power LEDs are a different story, but I think most people quickly learn not to stare directly into them.
I recall reading on wikipedia (always taken with a grain of salt of course) recently that current high power LEDs may represent a "blue light hazard", sounds possible to me and they do reference a source (actually theres a second source as well) both of which I have yet to read over.
Taken from here:
"There is increasing concern that blue LEDs and white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems.[31][32] "
I recall reading on wikipedia (always taken with a grain of salt of course) recently that current high power LEDs may represent a "blue light hazard", sounds possible to me and they do reference a source (actually theres a second source as well) both of which I have yet to read over.
Taken from here:
"There is increasing concern that blue LEDs and white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photobiological Safety for Lamp and Lamp Systems.[31][32] "
Black Rose
Flashlight Enthusiast
I bought a cheap 9-LED Dorcy on the weekend.
It's not a powerful light (3xAAA, states 40 hour runtime) but there was a warning on the packaging not to look directly into the light (i.e. corporate CYA statement).
It's not a powerful light (3xAAA, states 40 hour runtime) but there was a warning on the packaging not to look directly into the light (i.e. corporate CYA statement).
Alero
Enlightened
If it hurts, don't do it.
Gunner12
Flashaholic
The light would probably run down before any damage is done. I don't think there are any LED remotely close to the sun in lumen emitted per area.
Your child would probably learn that it hurts to look into bright lights and would learn to stop looking at bright lights.
Just be careful of lasers, UV and IR LEDs.
:welcome:
Your child would probably learn that it hurts to look into bright lights and would learn to stop looking at bright lights.
Just be careful of lasers, UV and IR LEDs.
:welcome:
Jarl
Flashlight Enthusiast
it's not so much lumens that counts, but intensity- stars emit far more lumens than your average torch (lol), but which would you rather have lighting your way?
I doubt it would cause permanent damage at that level, but a word of warning: when I was a little kid I liked to look at the sun (was into astronomy) and often did so on trips on the freeway. It didn't hurt my eyes at all when I did it. Later in life I realized that I had damaged my eyes somewhat, with a hazy area in the middle of my field of vision, and greater than average sensitivity to light. That hazy area has only relatively recently diminished or I am not able to see it anymore. I'm only 29, but it took a good 20 years for those effects to disappear. My sensitivity to light is still there, and I usually have to wear sunglasses or squint even on a cloudy day. Just so you know, I have excellent vision, but there are definitely those problems I've mentioned.
Telling your kid the dangers of looking into the sun is one of the few things I think parents actually should coddle their children with, as it's something that can very easily scar them permanently before they realize it's bad. My parents never told me not to look at the sun, and since it didn't hurt and I was curious, I did it. No, I never put my hand on the stove or cut a limb off with sharp objects, I never was an idiot. I was however curious like all children, and didn't know better about the sun.
Telling your kid the dangers of looking into the sun is one of the few things I think parents actually should coddle their children with, as it's something that can very easily scar them permanently before they realize it's bad. My parents never told me not to look at the sun, and since it didn't hurt and I was curious, I did it. No, I never put my hand on the stove or cut a limb off with sharp objects, I never was an idiot. I was however curious like all children, and didn't know better about the sun.
hank
Flashlight Enthusiast
Remember a "white" LED has a whole lot of its output in the blue range; see the LEDmuseum spectra for those. A red one would be safer as a toy!
PubMed found this on a quick look (there's probably more to be found)
40 minutes of exposure was enough to do damage in experimental work.
Question then would be how long it takes to heal, and whether exposure spread out is as bad as continuous exposure.
http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&uid=11692615&cmd=showdetailview&indexed=google
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA
I know there are some cases where ordinary eye doctors' eye exam lights caused blindness (when someone was left under the light while the examiner got distracted) and they're filtering those now to reduce the blue light, at least where I go.
It's not going to be painful in time to warn a kid off --- and I know as a kid I did too much staring into lights just so I could then watch the colors change in the afterimage, luckily those were low wattage incandescents!
PubMed found this on a quick look (there's probably more to be found)
40 minutes of exposure was enough to do damage in experimental work.
Question then would be how long it takes to heal, and whether exposure spread out is as bad as continuous exposure.
http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&uid=11692615&cmd=showdetailview&indexed=google
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA
I know there are some cases where ordinary eye doctors' eye exam lights caused blindness (when someone was left under the light while the examiner got distracted) and they're filtering those now to reduce the blue light, at least where I go.
It's not going to be painful in time to warn a kid off --- and I know as a kid I did too much staring into lights just so I could then watch the colors change in the afterimage, luckily those were low wattage incandescents!
Best not to do that. Young kids eyes would be more suceptible to damage. You could get a photon freedom, and turn it on to its lowest level, so that it just comes on. If you can look at the LED die without pain, then it should be alright.
Or a Novatac on its lowest level shoudl be alright too.
Crenshaw
Or a Novatac on its lowest level shoudl be alright too.
Crenshaw
Turbo DV8
Flashlight Enthusiast
If it feels good, do it.
Lite_me
Flashlight Enthusiast
I think Manfred Mann said it best...
Mamma Always told me not to look into the eyes of the Sun!!!! But Mamma, Thats where the fun is!!!
jtr1962
Flashaholic
Probably the greatest danger comes from looking at blue and especially UV LEDs in a darkened room. The danger is twofold. First off, shorter wavelengths are more damaging. Second, because the retina isn't particularly sensitive to deep blue or violet light the pupil will not contract to restrict the amount of light entering. It will remain wide open because of the darkness. At least a bright white LED will cause the pupil to contract, limiting the damage. While staring into any bright light for extended periods isn't a good idea, if you really must do it then make sure you do so in either a very brightly lit room, or outdoors in daylight. Your pupil will already be closed, and restrict the amount of light hitting the retina.
Another good idea if you're going to give children any lights to play with is to put in your mostly discharged cells (especially rechargeables which are close to needing a recharge). The nearly dead battery will inherently limit the run time, and hence exposure time. A brief flash in the eyes from a bright light isn't going to cause damage unless it's a laser, but children have a tendency to stare into lights for many minutes (I guess most of the adults here still have that tendency also ). A nearly depleted battery will make that impossible.
Another good idea if you're going to give children any lights to play with is to put in your mostly discharged cells (especially rechargeables which are close to needing a recharge). The nearly dead battery will inherently limit the run time, and hence exposure time. A brief flash in the eyes from a bright light isn't going to cause damage unless it's a laser, but children have a tendency to stare into lights for many minutes (I guess most of the adults here still have that tendency also
). A nearly depleted battery will make that impossible.HDS_Systems
Enlightened
To provide a bit of perspective, the surface intensity around noon in June on a clear day is roughly 120,000 lux (Tucson, Arizona, USA - southwestern desert). This is enough to cause eye damage if you look directly at the light source - i.e., the sun. The Ra Twisty at 100 lumens is generating roughly 375,000 lux at the exit aperture - using the same surface area. Looking into the exist aperture at close range exposes you to roughly 3 time the light as looking directly at the sun.
Granted, there is no UV, but bleaching does not require UV.
Henry.
Granted, there is no UV, but bleaching does not require UV.
Henry.
2xTrinity
Flashlight Enthusiast
True if the angular diameter of the light source at that distance from your eyes is 30 arc-minutes, the same as the sun. The source size will determine how concentrated that energy will be on the retina. I could generate a certain lux value using a bunch of fluorescent tubes, or a really intense arc light, the latter would be much more damaging to look directly at. Lasers are the worst, as they produce an infinitesimally small point-image.
In the case of the flashlight, there will be basically two relelvant "light sources" -- the image of the die on the reflector (a "large" source) and the die itself (a "small" source). For the sake of my post, Ill assume we're talking about the die alone, and not the reflector (the spill/light from the die is worse at close range.... trust me :sick2
The die will be approximately 30 arc minutes when the light is 17cm from the eye, assuming an apparent die length of 1.5mm. I know that the dome on a Cree XR-E makes the image of the die bigger than it actually is in reality, which is a square millimeter. If at 17cm distance the measured lux is 375,000 lux, the light will be effectively like a 3x brighter version of the sun. And in fact even then, the component from the reflector won't concentrate to a point as much as sunlight.
However, there is still another factor to consider -- pupil diameter. In a completely dark room, the pupil might allow in 50x as much light as in the case of someone staring at the sun on a bright sunny day. This BTW is the reason why looking at the sun during an eclipse is a particularly bad idea, as the sky is dark thus pupil is dilated more.
My suggestion is to replace the clear glass with a window that has some sort of diffusion film on it -- This will soften that harsh spill light coming from the die, and effectively make the "light source" a lot bigger/safer. Up close as a flood light, it will actually be more useful, as the light won't cast such harsh shadows.
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2xTrinity
Flashlight Enthusiast
True if the angular diameter of the light source at that distance from your eyes is 30 arc-minutes, the same as the sun. The source size will determine how concentrated that energy will be on the retina.
I coudl generate a certain lux value using a bunch of fluorescent tubes, or a really intense arc light, the latter would be much more damaging to look directly at.
In the case of the flashlight, there will be basically two relelvant "light sources" -- the image of the die on the reflector (a "large" source) and the die itself (a "small" source). For the sake of my post, Ill assume we're talking about the die alone, and not the reflector (the spill/light from the die is worse.... trust me :sick2
The die will be approximately 30 arc minutes when the light is 17cm from the eye, assuming an apparent die length of 1.5mm. I know that the dome on a Cree XR-E makes the image of the die bigger than it actually is in reality, which is a square millimeter. If at 17cm distance the measured lux from the flashlight is 375,000, the light will be effectively like a 3x brighter version of the sun.
A bare LED at that distance, assuming no reflector and a 90 degree beam angle, would produce roughly ~2000 lux. However, there is still another factor to consider -- pupil diameter. In a completely dark room, the pupil could very well allow in 60x as much light as in the case of someone staring at the sun on a bright sunny day. 2000 x 60 =120,000...
Adding a reflectro could certainly increase the lux, but it's also true that the light from the reflector won't be as concentrated when it reaches your retina, so that's why I didn't factor that in.
However, I will say this -- I once built an aspheric mod which I would NEVER want to look at directly. It was uncomfortable to look at through closed eyelids. Looking at the sun with closed eyelids does not produce nearly the same discomfort. So think about that for a while :sick2:
To the original poster: my suggestion is to use a light with a light diffusion film on it. Then the "light source size" will be much larger, and the light will be much safer (not as throwy, but thats the breaks).
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