Light spectrum question. Damage to the eyes

[ShelleyBoston]

I was looking at the specifications of some LED fixtures and I noticed some LEDS are in the UV spectrum from about 370-400nm this frequency falls under the UVA spectrum so I was wondering if anyone know of any studies done
on the "possible" harmful UV radiation exposure of LEDs specially since we stare at our tanks, UV light can't travel far in water but at depths of the average tank (12-15 inches) we maybe getting enough radiation exposure to raise a concern.

 

[dz6t]

I am wondering which LED has UV spectrum below 400? Thanks

 

[ShelleyBoston]

even at 400nm exposure you run the risk of cataracts of the lens, retinal burns and skin cancer, most LED lights go down to that range and I was looking at some Chinese fixture on Ebay that have have a lot of power probably way beyond the safe limit and the specs show graphics starting in the 380nm.

 

[dz6t]

I mean LED light for reef tank.
AI Hydra has 400nM as the shortest wavelength,
Radion at 405nM
GHL Mitra's at 420nM
The Maxspect razor at 410nM
Reef Breeders at 410nM
Kessil is unknown but by looking at their published spectrum, estimated around 400nM

 

[dz6t]

UVa and UVb

 

[dz6t]

Coral do benefit from UV below 400nM but these is not worth the risk to get skin cancer.
Technically all major LED have near UV spectrum but not truly UV.

 

[ShelleyBoston]

My cencern is the lower end of LED-light spectrum (for reef aquaria) 400-420nm I am sure after a certain x number light output it can't be good for the eyes, the question is do we know how safe they are? How much light ouput is safe? and what is the minum effective dose that will keep the corals happy and our eyes safe..

 

[reefstarter]

UV and red both die out pretty quickly in water and LEDs don't produce enough to cause any issue unless you stare st them. Halides and t5 maybe but I doubt it corals can benefit from uv but too much can be bad just like with any life so I am sure they are not that strong Dong knows his stuff I researched reef lighting for hours a night for months looked at people's tanks and even looked in to using sunlight

 

[Fishport]

I think this is a reasonable question to ponder for these reasons.

1-Yes water attenuates light transmission but ultraviolet is the least affected.

2- If you read Dana Riddle's articles you realize that spectrum ratings and meter readings often have arbitrary cutoffs that do not reflect UV spectrum.

3- Since we do not perceive UV our pupil's do not close in response to the amount of light. I don't know if this explains why some people develop visual fatigue and headaches from exposure to the violet spectrum lighting used at frag swaps, etc.

4- Light and even LED's are in the analog world. There are no abrupt cut-offs at 400 nm. So an emitter may have most of its energy within the rated spectrum but that does not mean it does not emit light at wavelengths above and below its rating, though this is greatly reduced with LED's.

5- I am not aware of any measurements of light radiation reaching the viewer of the tank. So I am not sure if we have all the facts to reach a conclusion.

My suspicion is that Dong is right. Those last three words are usually a safe bet on this forum. But I am not convinced we have a good enough factual basis to dial up the UV in our LED's without consideration of its long term impact on our eyes. This is relatively new technology, let's consider that we don't yet have the experience and data to consider it completely risk free. If you have young children remember not only might they be more susceptible to injury from UV light, but due to their height, they are looking more directly into the lights.

 

[Greg Hiller]

Heh, maybe this is why I cannot stand to look at the displays with all the LED lights that make the tank look like the light show at Disneyland.

 

[mitant]

How do you feel about high-powered point source lighting like Kessils or Ecoxotic Cannons? These types of lighting can be positioned in a manner that would presumably reduce the likelihood of optical damage to shorter people, or crouching people.

You could position the lighting above and to the front of the tank, angling it downwards. If your ceilings were tall enough. or positioning was smart enough, standing in front of the tank wouldn't cause a shadow.

 

[ShelleyBoston]

I found this note interesting from Cree LED... http://www.cree.com/~/media/Files/C...p/XLamp Application Notes/XLamp_EyeSafety.pdf

 

[dz6t]

Heh, maybe this is why I cannot stand to look at the displays with all the LED lights that make the tank look like the light show at Disneyland.

+1, It hurts my eyes looking at all blue LED at Disneyland...err...frags swaps (except no much swapping done there)

 

[dz6t]

I found this note interesting from Cree LED... http://www.cree.com/~/media/Files/C...p/XLamp Application Notes/XLamp_EyeSafety.pdf

Great note.
Thanks

 

[Fishport]

Here is some data from Dana Riddle about the actual light spectrum from a "UV" Led with a rated peak output of 400 nm. For the full article that examines the broader topic of coral response to light spectrum see-
http://www.advancedaquarist.com/2014/5/aafeature

from Dana's article
'Ultraviolet' LED - Peak Output: 400 nm
The term 'ultraviolet' is something of a misnomer in this case, if we recognize the definition of violet light as being those wavelengths between 380nm and 430nm. In this case, practically all of the radiation produced falls into the 'violet' bandwidth. Interestingly, ~40% of the LED's output will not detected by PAR meters with a cutoff of wavelengths below 400nm. See Figure 8 - 10, and Table 4.


Figure 8. Spectral characteristics of the 'UV' LED.


Figure 10. Output of the 'UV' LED per 10 nm bandwidth.


Table 4. Radiation production of the 'UV' LED per 10nm bandwidth, expressed as %.
Wavelength, nm Percent Wavelength, nm Percent
350-359 0% 420-429 3%
360-369 0% 430-439 1%
370-379 0% 440-449 0%
380-389 2% 450-459 0%
390-399 37% 460-469 0%
400-409 44% 470-479 0%
410-419 11% 480-489 0%
--------------------------------------------------------

So although there is radiation at wavelengths below 400nm, they seem to diminish quite rapidly.

The CREE article is interesting. Thanks for posting it. If I read it right, there still is a moderate risk from "blue light exposure" with the blue spectrum LED's and there is also blue light exposure from white LED's but that has not yet been evaluated. In addition there is risk of overheating the retina from light intensity over a very broad light spectrum. Bottom line, be aware of the potential and be cautious with the heavy use of blue and violet lights lights for long term viewing of your tank. It would be terrible to lose the joy we derive from observing the life and colors of our reefs.
Ralph

 

[ShelleyBoston]

I guess we could always wear polycarbonate goggles, like the ones we use in our lab for UV exposure.
they about 36 dollars on Amazon and they shield from about 254nm up through the violet and blue spectrum. You can wear glasses under them too.
UVP98 is the model number. I wonder if they would work for looking for extended periods..

 

[dz6t]

In this hobby, color are very well misrepresented, LOL
May be Ultraviolet in LED means: Ultra Violet, very very violet,

 

[Fishport]

"I guess we could always wear polycarbonate goggles, like the ones we use in our lab for UV exposure."

That look would really earn one the title of a
"Reef Geek"!



(modified original work of Theresa McCracken)

 

[Steviereefs]

So according to Cree data the chip
XR-E Royal Blue is a doozy

 

[Steviereefs]

I have had this Apollo 6 style fixture for a month or so and the blue bothers me alot just observing my tank when they are on alone when I back away after observing for awhile my eyes feel irritated when I close them. If you don't believe it you can come over my house and try it yourselves . It bothers me because I've always had perfect eye sight and would hate to ruin it because of a stupid light.