1. 6000 lux is a _lot_ of light.
2. The LEDs tested are not the "warm white" (1500-2500K) commonly used as replacements for incandescent bulbs in the US. They're the "blue white" (>4000K) ones, or pure blue or pure green at specific wavelengths.
With those constraints, it's an interesting result. It does not mean you need to run home and rip all the lights out, though.
But even so, the high energy spectral content of indoor LED lighting is much, much less than what you see from direct sunlight. If LEDs are really a vision risk to the modern office worker, they're significantly less so than the same risk of agricultural or other outdoor workers.
But, just to play devil's advocate, it seems plausible that sunlight might activate some kind of defense mechanism in the eye that protects it from the effects of the higher energy part of the spectrum.
If nothing else, the overall brightness levels would cause your pupil to shrink more in sunlight than under LED lighting.
However, the ganglion cells that influence dilation and melatonin happen to be mostly sensitive to blue light (~470 nm), so in theory this would only be a problem for LEDs largely concentrated at even shorter wavelength.
I have worn polycarbonate lenses my whole life, well since infancy. Polycarbonate lenses block UV light. If I go outside without my glasses or sunglasses my eyes hurt, even in winter. I don't know if my eyes are super sensitive or they just aren't used to the UV light and the micro-damage it causes.
 My email's in my profile if you'd prefer not to say publicly, although since a few others upvoted my comment it looks like it's a popular question :)
(The idea there, if you're curious, was to build a light collector with a relatively wide incidence angle that'd focus the beam onto a mostly decapsulated violet LED reverse-biased to act as a photodiode and tied to the base of an NPN transistor, so as to switch a GPIO on my entertainment center Raspberry Pi and use the laser pointer as a kind of remote control. The circuit worked quite well when illuminated, but a ~1mm target is hard to hit from ten feet away, hence the messing about with focusing optics.)
I don't have a detailed characterization of the injury because I'm rather overdue for an optometrist's appointment, but later experiments with the same configuration (and goggles!) showed that, so focused, the beam would deform and start to burn black ABS plastic within a few seconds, and took no perceptible time to burn a hole in a sheet of black construction paper, in both cases producing damage in a radius well under a millimeter - I found that, unless placed precisely in the focal plane, the beam was too widely spread even to raise smoke from the paper. The effect on my retina would therefore have had to be the same sort of closely localized heating, a hypothesis borne out by the effects I observed to result.
Beyond the pain already described (which lasted a good couple of hours), those effects included the click sound I mentioned, which I believe to have been produced by the sudden vaporization of a small volume of aqueous humor adjacent to the retina, and a quite noticeable but thankfully non-foveal bright green floater which did not cease to be perceptible until about a month had gone by. Whether this latter is the result of the injury healing, as I gather such minor retinal injuries often do, or rather of my visual cortex having grown a new filter, I won't know until my next slit-lamp exam.
(And I own a pair of wavelength-matched laser goggles now, as should you if you're going to do anything at all with a laser and any kind of focusing optics. Carelessly enough handled, even a 5mW pointer beam can pose a real risk. Don't make the same mistake I did!)
Fascinating though it was, I have to say I found the experience with very little to recommend it, not least because it disquiets to realize that the click you've just heard, conducted through the bone and tissue of your head, was produced by a small volume of fluid inside your eyeball suddenly boiling.
1) Flicker: does the LED's high-speed flicker play a role in damage to the eye? (Here's an LED viewed in slow motion: https://www.youtube.com/watch?v=3wdljou1M8Q)
2) Spectrum: LEDs can have very uneven spectrums with spikes at particular frequencies (particularly in applications like street lamps that don't use phosphors). This is something an eye in nature would never experience.
Here's a great video showing LEDs strobing compared to other bulb types: https://youtu.be/1IDf16R_eJ0?t=13s
In the living room or especially the bedroom and bathroom, I prefer dimmer lighting with less blue spectrum. My 29W halogen incandescent on the night table doesn't exactly burn through a lot of electricity and has the most pleasing light in my eyes. Until there's a LED that can perfectly match that, I'll stick with that until these bulbs get banned, too.
Or, do what I did. Just make the rectifier directly out of LEDs itself - https://www.youtube.com/watch?v=jDnCHyF7o5U And from there you can power your devices with the leftover DC power.
LEDs are seriously far more robust than they were a decade ago.
That's not PWM in the video. That's raw mains frequency.
Here's one directly on the mains power. NO CONTROL CIRCUITRY.
Sodium lamps are much less objectionable because their spectral spikes are at much longer wavelength.
The only sodium lamps I'm familiar with are high pressure sodium, which emit a garrish orange hue.
https://www.youtube.com/watch?v=l6bTSJVLCVI - I used to build fully-functional hydroponics buildings from the foundation-up. Electrical included.
Ground is for safety in AC, when there is a short the ground should take the current away resulting in power loss through the earth that in turn makes the breaker flip. Without grounding the wire that is exposed and touching something will (depending on material etc.) not transfer any current because of too high resistance, then as you touch it it will shock you and then the breaker will go off.
(A loss power breaker, not a draw power breaker)
Perhaps you mean the neutral?
Same way you complete any other ground - since ground and neutral are literally on the same leg (go look at any installation. You've got TWO wires coming in at the mains, ungrounded.)
So, tell me, how do you ground those ungrounded 240/277V wires??
You don't. Both of them ARE the natural ground dependent upon whether you're at the peak or trough of the waveform. That's kinda how AC works.
Where I am from we have installations differently.
phase and neutral come in the box, they go through a loss breaker(RCD) and then split up in to multiple breakers.
Then those wires go to the socket.
Then near the box there is a metal rod in the ground with a wire going to the box, this wire connects to the ground wires coming from sockets.
The ground wire, is not connected to anything but things that are not supposed to have any power flowing through.
Yes Neutral is grounded (outside my house, on the main)
But when we say we ground things we mean the third connection.
Sorry, didn't know it was so different over there.
edit: Saw the correct name for the "loss breaker" in other post, it is RCD :)
edit: Question, what happens if you hold the neutral to the ground wire there?
Forgive my ignorance, I'm no electrical expert, but did you just say that the ground wire is connected to the neutral somewhere in the circuit? Or did I misunderstand you?
EDIT: That "always" is assuming the house is modern wiring and not older-style two-prong wiring for the wall outlets. Those systems were just main and neutral at the box and controlled by a fusible link.
If I'm understanding you correctly, in the US the ground wire is functionally identical to the neutral due to the bonding. Therefore (this is my own deduction and I'd appreciate being corrected if I'm wrong) you could, in theory, invert the ground and neutral wires in the plug of an electrical appliance and there would be no change in the behaviour or safety of the appliance?
Generally, no. I've seen backwards wiring jobs cause 48-80VAC to run through the casing of microwaves (they usually use the casing as a floating ground.) Any wiring inversion will usually cause some issue somewhere.
There are no results which say that our eyes are safer outside.
If you meant:
"if we're safer outside
if we've a defense mechanism
then we'd be safe
That's already two "If"s deep and not a reasonable position to take :)
Those outdoor workers probably ought to be wearing UV-blocking sunglasses regularly to avoid increasing their chance of cataracts:
My optometrist was quite emphatic about this because she said the damage is thought to be cumulative, so if you're going to have a lifelong outdoor career or avocation, the difference could be significant.
I do think the theory elsewhere in this thread about the different spectral distribution could be significant. This is why apparently non-UV blocking sunglasses can make UV damage worse: the pupils open wider when visible light is blocked and so let even more UV in. If you just skew the spectrum of some light source toward the UV without increasing the overall luminous intensity, presumably it could cause some health risks in a similar way.
There is nothing inherently bluer about LED technology. LEDs are readily available in color temperatures down to 1600K.
The ratio of yellow to blue light determines the colour temperature perceived. Some of that blue light will always get through, so white LEDs (even "warm" ones) will always have a blue light component to them.
But LEDs get a bad rep because there are so many garish blue-white, flickering, junk ones flooding the market.
Most people today buy the much warmer ones so they don't feel like they're in a mental institution.
Mine were a gift, but I use them as protection from sun as well. Even dim, cloudy days expose you to far more blue light than a PC monitor.
After spending thousands on eye surgery, I'm back wearing glasses to protect them.
Hopefully this turns out not to be a big deal. Having to choose between depression and retina damage would sure suck :/
This article explains some of the tradeoffs at the specific wavelengths.
The last time I went down the list of references I was personally not convinced, but not my field...
I couldn't find the exact brightness specifications, but I can testify that it is very bright on the max level.
Using the Philips line for an example, something like a blend of the Philips HF3520 Wake-Up light and the goLITE BLU HF34xx models?
Someone else was nice enough to post a link to the paper:
Overall, I think the focus should be on light spectrum, not LEDs per se. Warmer LEDs has far less direct emission, with most of the light being re-emitted from the phosphor.
Daylight ranges up to 120,000 lux, so 6000 is several times the lighting in most spaces, but still nowhere near bright sunlight.
That said, from the abstract (I don't have journal access), it sounds like they found a result in both 24H high intensity, and in on/off "domestic levels".
Is the 6000 lux you mentioned their value for high intensity, or is that what they considered as domestic levels?
On the other hand, by exposing the same animals to a luminous intensity similar to that usually used in dwellings (500 lux) for 24 hours, only the LEDs appeared harmful
We don't usually stare at light sources; we use them to illuminate objects. A 100W incandescent from 1 meter on to reading material or other work is considered fairly brightly lit, and that's not getting the full 100 lux back to your eyes - only what the surface reflects.
Daylight is far brighter, but most of us have been warned from early childhood about the danger of staring at the sun. 100,000 lux may be present, but we're not directing it in to our eyes.
4000K isn't "blue white" or even what's usually called "cool white". It's warmer (that is, more weighted toward the yellow-red end of the spectrum) than sunlight at midday (5000K-ish) and much warmer than LED and fluorescent sources that are noticeably blue (6000K+).
Beyond that, sources with a flatter or fuller spectrum (most commonly measured as color rendering index, or CRI) will have less of a blue peak even at cooler color temperatures.
And yes, 6000 lux is a lot of light. Staring at a 100W incandescent light bulb from 1 meter away will put about 100 lux on your eyes, by way of comparison.
That puts 6000 lux firmly in the "my eyes hurt, this cannot be good" category.
They had also dilated the rats' pupils with atropine, making the acute exposure test equivalent to, or perhaps worse than staring at the midday sun for 24 hours straight.
Even the lower-level chronic exposure test used 500 lux with light from all directions so there's no way to look away. We don't use light that way in reality, and while I'm sure the intent was to accelerate the test, I can't help but suspect it's the equivalent of testing whether bathing in warm water might be harmful by boiling rats alive.
> The data suggest that the blue component
of the white-LED may cause retinal toxicity at occupational
domestic illuminance and not only in extreme
experimental conditions, as previously reported.
The domestic illuminance they used was only 500 lux, which they describe as the "domestic classic light intensity".
It does however, seem much more likely that this is to do with extra energy in the UV end of the spectrum, which IIRC WW LEDs cut a lot more of (as well as the additional, visible blue light that makes CW seem so much brighter).
I didn't know about this mysterious sci-hub, but now I do.
More info on sci-hub: http://bitesizebio.com/28268/access-science-free/
Compared to these, I can conclude that my home LED lights likely strobe in kHz range or above, or maybe not at all.
I can't speak for you but I find the full-wave rectified ones not to be a problem. Of course the difference isn't just the doubled frequency, it's also a much higher duty cycle.
Not terribly scientific, but pretty relevant when transferring this knowledge to humans.
So 6000 lux of blue is approximately 30x as many green photons. For blue LED plus yellow phosphor that 30x "yellow" will be the signal that you will use to decide "that's enough light to perform work."
The rat's eyes were definitely cooked by all of the blue. Imagine if they had used near UV or near infrared LEDs and the same meter to calibrate the intensity. Cooked rats.
From the article:
we investigate, in albinos and pigmented rats, the effects of different exposure protocols
It's much too soon to rip out the lights in any event.
> We used two types of lighting devices. For exposure to white LED, commercial cold white LED panel generating 2300 lumens during 24 h was used. The LED panel was placed above 8 transparent cages, placed on white surfaces, leaving enough space for air circulation and constant temperature maintenance at 21 °C. The illuminance measured at the rats’ eyes position was 6000 lux (Photometre DT-8809A, CEM, China).
> For long-term exposure, specific devices were built and characterized by Statice, France (Fig. 1A). Metallic boxes contained rows of LED with a diffuser in order to improve the directional uniformity of the radiation and avoid punctate sources. Alternatively, CCFL or CFL were uniformly distributed around the metal cages. Each cage was placed in a metallic device that was then placed in a ventilated cupboard allowing for a constant 21 °C temperature control (Fig. 1A). The light intensity was controllable and the distribution of light in the cage was homogenous whatever the rat position. Different types of LEDs were used: cold-white LED (pure white 6300 K), blue LED (royal blue 455–465 nm), and green LED (520–35 nm) (Z-power LED, Seoul Semiconductor, Korea). Exposure intensity was spectrophotometrically measured by Statice.
> Exposure protocols
> Acute exposure: LE and W rats were maintained in a cyclic light/dark (250 lux, 12 h/12 h) environment for 21 days. The day before light exposure, rats were dark-adapted for 16 h. The next day, pupils were dilated with 1% atropine (Alcon, Norvartis, Rueil Malmaison, France) under dim light, and rats were isolated in separate cages containing enough food for one day. After 24 h of exposure, rats were placed again in a cyclic light/dark (250 lux, 12 h/12 h) environment for 7 days and sacrificed for histology and immunofluorescence analysis. Control rats were submitted to the same pre conditioning protocol but not exposed to light. Different types of light sources and light intensities were used as detailed in Fig. 1B. For cold-white LED, different light intensities were tested from 6000 lux, to 1500, 1000 and 500 lux. Blue and green LEDs were used at 500 lux which is the domestic classic light intensity. CFL was used at 6000 lux and 500 lux, CCFL at 6000 lux. Illuminance was measured at the level of the rat eye.
> Long-term exposures: Rats (LE and W) were maintained in a cyclic light/dark (250 lux, 12 h/12 h) environment for 21 days, then placed in specific cages for chronic cyclic exposure to different types of light at 500 lux: CFL, white, green and blue LEDs. Animals were sacrificed right after 8 or 28 days of exposure. For the long-term protocol and in order to be as close to domestic light as possible, rat pupils were not dilated.
This sort of thing should have had 2 control groups. One kept in the dark, the other exposed to the light protocol they used for artificial lighting, using natural sunlight as the light source.
Its not clear from the wording above exactly how the control group was exposed in pre conditioning, and what the nature of their post exposure protocol was.
500 lux in cyclic test is not outside the realm of reason for representative real world exposure.
Personally, I'd like to see a control under natural sunlight, and one under a man-made filtered blackbody radiator.
Anyway, I wonder if these guys got a follow up grant, does anyone know?
I wouldn't be surprised to see that this study is never reproduced.
Another guess: they might actually find similar retinal problems from sunlight exposure in people who spend most of their working life outdoors, but since most people in developed nations don't work in agriculture anymore their baseline population doesn't reflect a lot of sunlight exposure.
(IIRC blue and violet LEDs are close to 100% efficient, but our eyes are much more sensitive as the wavelength gets farther from violet. This means that the "efficacy" of less violet LEDs is much higher. The backlight power will be set to achieve some desired apparent brightness, so a longer-wavelength blue primary would save power.)
Long-term exposure to LED at 500 lux, in cyclic
(light/dark) conditions induced retinal damage only in albino rats but not in pigmented rats
So, at household levels WITHOUT artificially dilated eyes, only the albino rats (who one would assume are more sensitive to light) suffered any damage.
Given that, as another commenter mentions, rats are likely to be more sensitive to light than humans anyway, this looks like it's a reassuring rather than concerning result. Just don't artificially dilate your eyes then stare at a super-bright LED bank for 24 hours!
Looks like my weekend plans are shot
I just tried for a couple of weeks a visor style light that is just over 500 lux at 500nm dominant wavelength (blue-green; it looks green and is a longer wavelength than most such devices). While it didn't seem super bright, it did seem fairly bright and actually caused me mild pain, similar to what bright light occasionally causes. The lower 315 lux level did the same at first. I started with that a few days and it seemed like my eyes adapted quite a bit so I moved to the higher level. I got spooked after noticing the pain later in the day one day after using the visor on high in the morning, so I haven't tried the lower level again to see if that still causes pain. The manufacturer said that in studies about 3% of people report that problem.
Anyway, it seems to me that my use of the visor might be similar to the lighting in this study. I haven't noticed this issue with other artificial lighting, although I haven't been around LEDs that much that I know of, mostly compact flourescents. The closest is a led light alarm clock that I have stared at at close range for a while and is listed at 300 lux, although I'm not sure if that is what I am getting even a few inches away. The visor light does have a 50-166 hz pulse so that could be related; I'm not sure about the light alarm, but I never noticed that flicker the way the visor does.
Anway, 500 lux at eye level at least can be quite a bit different than normal lighting.
I'm oversensitive though. E.g. slightly flickering energy saving lamps make me dizzy, exacerbated by ACs making my eyes dry (hello, Ikea).
I hope those nano-coated regular light bulbs will become a thing.
Poor quality LEDs are awful - the 50/60Hz flicker/strobe effect that many produce is very annoying and fatiguing and it doesn't surprise me that they're considered a health hazard.
Try quality LEDs and you won't regret them.
Incandescent lamps are typically ~2500K CCT
Quality certainly doesn't mean Brand-name in this day and age of unscrupulous law-buying companies.
Actually, it's a great measurement if you only work with the monochromatic ones. Knowing the LEDs efficiency at bin testing conditions will tell you what to expect - E.G. high-bin 3w 460n LED with 50% efficiency at 3w drive and typical operating temperatures (~70C junction temperature) means you can expect 1.5W of light. We toss in Avogadro's constant and a couple other formulas, do some multiplication, and suddenly we know roughly how many photons are being put out.
This gets harder with white LEDs as one must figure out the relative percentage of each wavelength comprising the light, basically forcing you to do the math a few hundred times over, but it's still rather reliable. I just do rough calculations in my head for White LEDs.
5 years for a product that is advertised as lasting for decades as this usage rate.
Tubes? Presumably you're talking about CFLs, not LEDs? 5 years ago, household LED lamps were still in their infancy and were really expensive.
My experience with CFLs was pretty similar to yours. They didn't last, and dimmable ones especially would often fail within months. And the quality of light from fluorescents was never all that good anyway.
But out of around 25 Philips LEDs I've installed, most of them dimmables, not a single one has failed or had any problems so far. The oldest ones were installed around a year ago now.
So much of a crapshoot.
As you research, you'll discovered that there is in fact more to the single CRI value. It is actually an average measurement of a range of different colors. R9 in particular is the one that is hardest for LEDs to reproduce. Some manufactures goose their CRI value by getting high scores for the other values even though their R9 or R13 (skin tone) is poor.
Also, a neat fact: all CEC qualified LEDs are high CRI.
(P.S. I bought a GE Reveal once and it had the worst color fidelity I've ever seen. Some normally bluish surfaces were distinctly green. I don't understand how it has a high CRI.)
In short, I wouldn't trust GE for LEDs. In fact, I'm so disillusioned with almost every company out there (Cree, Philips, GE, Sylvania) that I've simply gone back to building my own lights for my specific purposes. I can't trust any of these companies to be accurate or truthful in their marketing.
Is this what your username references?
Making daylight is easy enough. The Nichia 219B LED in 5000K R9050 (CRI 90+, R9 50+) is beautiful. 12-18 of them will comfortably make over 5000 lumens without having to be driven especially hard. It's not terribly hard to come up with options to wire them up and heatsink them properly either.
What I haven't been able to find is a suitable power supply and driver. I want to plug it in to 100-240V and have a dimmer knob giving me 5-5000+ lumens via current regulation, not PWM, though very fast (> 10kHz) PWM might be acceptable. Yes, I'm aware the tint will shift a bit through the brightness range without PWM. I'm OK with that.
Infinite? Not happening, but if you want to get CLOSE, your best bet is in a simple benchtop voltage and current regulator. I use four Nichia 219B LEDs to light my 55-gallon aquarium, are you SURE you really need 5,000 lumens? You could probably get away with just four of those, a fixed 12V power supply with adjustable current, and be done with it, they're ungodly bright and a quad of those can match up with the Cree MK-R.
I'm sure I want over 5000 lumens. When I want my room well-lit to promote a sense of alertness and compensate for shorter days in winter, my best current option is a flashlight that produces about 4200 lumens bounced off the ceiling. No, that's not one of those BS marketing numbers: the light is a Jetbeam T6, which in stock form uses four Cree XP-Ls powered from four 18650 Li-ion batteries. Independent tests, including my own have found its claimed performance to be accurate. I swapped the XP-Ls for Nichia 219Cs (5000K, CRI 80+, R9 unspecified) and measured about a 2% loss of output, but increased intensity. This works as a room light, but requires an external cooling fan to run on high for longer than about 10 minutes (it has a thermal sensor and stepdown), and the batteries can only keep up with that output for a bit over an hour. 219Cs are more efficient than 219Bs and can be driven much harder, but aren't as pretty. Even the recently-released R9050 (CRI: 90+, R9: 50+) version just doesn't look as nice to me.
Four 219Bs definitely can't produce 5000 lumens. The 90+ CRI versions peak at about 600, but I don't want to run them at peak output; the harder they're driven, the stronger the spectral peak of the underlying blue LED. I want to run them at about 300lm/ea. 12 of them will get me that, but I'd actually rather have more than 5000 lumens.
Thanks for responding. I was hoping for an off the shelf driver, but it looks like I'm going to be improvising a bit more.
It's also difficult to find the 048Z available in single quantities. I didn't find the R9050 version on Octopart, Other versions cost $50-60, while 219Bs in several tints are readily available from suppliers of DIY flashlight parts for $3/pc. Getting 219Bs and triple or quad copper MCPCBs is easy, and they can be configured for any multiple of about 3 volts, while the 048Z requires a 50 volt power supply.
I was expecting to spend over $100 when all is said and done.
Just ask Nichia for an engineering sample. :) Boom, free sample if they've got one for you to utilize. I don't know how many Cree, KingBright, Nichia, Osram, and Epistar LEDs I've got just because I ask to test them.
As for the 50V power supply, it'll run on a 48V 1.25A driver. You'll be fine and those are about $20 each.
(Sorry if this is a dupe and hope this link is persistent, I scanned the thread and saw some people lacking access and didn't see any sci-hub post)
I wonder what the results would look like for warm LEDs ~ 2700K. I used to be a Cold-white aficionado but moved to warms for everything. If I experiment by suddenly switching between my cold and warm lights its pretty jarring (warm seems more relaxing).
I can however tell you a few facts about rat eyes.
- Their eyes are sensitive to ultraviolet.
- They have a dichromatic vision, two sets of cones instead of three. (some short wavelengths of ultraviolet/blue and a lot of greens)
- They cannot reshape their lenses.
- They have a lot more photo-receptors on their retina than us.
- They are something between farsighted and nearsighted.
- Poor binocular vision but big field of view.
Albino rats have more differences but I doubt they would have used any of those in a study on eyes.
Rats do get the same kind of eyes disease humans do (cataracts, etc.) however their sensitivity to light is really different. I don't think that it is ideal to use such different eyes to test LEDs sensitivity.
For example, here is a 2014 study, "White Light–Emitting Diodes (LEDs) at Domestic Lighting Levels and Retinal Injury in a Rat Model" http://ehp.niehs.nih.gov/1307294/
This article cites numerous studies in the quotes section ( scroll down) http://lowvision.preventblindness.org/daily-living-2/artific...
Links to eye toxicity, macular degeneration, and blindness are not the only problems associated with new lighting either, which tends to be very heavy in the blue components. Lots of research links usage of blue-heavy white lighting to damaging circadian rhythms, which can lead to significant health effects. https://www.sciencedaily.com/releases/2011/09/110912092554.h...
This year the AMA issued a public safety warning regarding LED street lights because of the association with circardian rhythm disruption and related health effects. http://www.cnn.com/2016/06/21/health/led-streetlights-ama/in...
Paul Jaminet has stated that circadian rhythm disruption has been more strongly linked to cancer than any food study, ever.
I use the GE Align PM LED bulbs, available on Amazon, which cut out most of the blue frequencies and largely address both sets of problems. Highly recommended. https://www.amazon.com/GE-Lighting-93842-350-Lumen-Dimmable/...
EDITED to correct summary of AMA announcement.
Otherwise my eyes start watering after awhile and get itchy and irritated. I think I must be sensitive to blue light. I used to set it around 4500 color temperature but now I lowered it to 4000.
* I made a simple website using the Notifications API which reminds you every 20 minutes to take an eye break.
> I think I must be sensitive to blue light.
My eyes hurt after a few minutes of looking at my girlfriend's iPad/computer screen. She's the opposite and thinks my screen is constantly stained yellow.
This is the case for noise related hearing loss. Everybody loses hearing acuity a bit as they get older, but exposure to noise accelerates this process. Exposure to ambient sounds in the high 60s (decibels) is harmful to a small segment of the population. That's not very loud, but fortunately most people are not hurt at that level. Occupational exposure levels are set considerably above that point.
I have this exact same model and it has been working great, too bad if carrying a significant risk.
The other situation would be artificial gardening system where a heavy bended light spectrum is used to grow lettuce etc.
This pulse laser was so powerful that at discharge through the microscope it could create a white spark in mid-air; the
so-called waist area.
I Hired on to CooperVision as a Developmental Tech, I inadvertantly grounded a flash-circuit while the laser exit face
aligned to my eyes.
The Fluke Meter actually bounced a centimeter into the air at discharge, and I saw a moderate orange glow for a bare
Immediately after, and today, when I gaze into a clear blue sky, I see a "small dounut shadow" of two to three degrees
in my mid to lower right field.
The contrast of the Donut image has decreased over the years but decades later, I see it.
What do you Know? I got shot with a surgical welder.
-No worries though, No worries at all.
Color temp = 5000K. Output is 13000 lumens. The sales page assumes 10 ft x 15 ft illuminated area (install height not specified but probably 8 ft) = 250 ft^2 or ~23 m^2.
Doing the math yields 565 lumens / m^2. Should be a little more at standing (eyes ~5ft off the floor) height.
Philips GoLITE BLU - https://www.amazon.com/Philips-GoLITE-BLU-Energy-Light/dp/B0...
30 minutes a day at the highest setting...
If I happen across that booth again, I'll stop and look.
I often fall into the trap of thinking that light at normally encountered levels has essentially no effect. That's obviously not the case though.
Blue LEDs can seem almost blinding.