Near UV LED's

[TropTrea]

I have exerimented in the past with near UV LED's in the 380 to 410 nm range and was very unhappy with them. However I'm still looking for something with a shorter wave lenght than the 454 Royal Blues to suplement with. What would be ideal would be a 435nm LED but I doubt if that animal exists. I have seen notes though of individuals that used 410 nm and 430 nm LED's. Does anyone have info on who manufactures LED's in the 420 to 430 nm range. Or any links to where I can find some preferably on star mounts?

[pnavarro170]

im looking into this also. first off what was it that you were unhappy with and why ?

i just ordered a maxpect razor that comes with 410/420nm leds, i think they are necessary for corals to retain their color. but i dont know for sure untill i try em.

I would love to go with a radion pro but a bit out of my price range at the moment. that one comes with 415nm leds and separate 405nm leds.

Im even thinking of adding an ebay pendant style uv led thats 20w of supposed 400nm spectrum to add to my razor.

[E Rosewater]

Steves LEDs has a 420nm LED. I have 15 of them in a 113 LED build. I don't notice much of a difference from them, I wish I had put a few more of them in. It's a good spectrum to have for photosynthesis though.

[TropTrea]

My experiece earlier with two different UV led's I tried were that everyone asked why are the lights on my tank so pink? I was only using them in a ratio of
1-near UV
2- Royal Blue
2-True Blue
1- Neutral White

I pulled the UV's and was much happier without the pink tint especialy on my sand bottom.

Besides this I did considerable research on how corals react to various parts of the light spectrum. I found that in nature there is basicly no light at shorter wave lenghts than 400 nm reaching the corals. The strongest peak of light is roughly 440 nm in nature but is strong in the range of 420 to 480 nm. Light at 380nm or shorter is extremly detrimental to all living cells and even in small dosages now is said to be a prime cause of skin cancer.

So with my present lighting with my blues being at 454 nm and 460 nm the real spread is between about 444 and 470 nm. This leaves a gap between 420 nm and 444 nm I'd like to fill. Ideal in a perfect world a 432nm LED would be ideal for this.

[Whitebeam]

I seem to remember that ac-rc do a 430nm 20W multichip if that's any use. Quite expensive though :-(

Peter

[TropTrea]

Yes I did get to the page everyone was pointing at. The 420-430 nm LED they offer seems to be very close to what I'm looking for. However on some threads I was told to keep the ma lows since the plastic UV protection lens does melt. I'm running my other LED';s on this new build at either 1,500ma (blues and royal blues) and my whites at 3,000ma. So I will have to run these on a seperate driver. Will probably use a 350 ma Driver on them since I do not want a lot of light in that range.

My original plan for my 120 gallon was to run
70 Watts of Neutral Whites (7-10 watt chipos)
60 Watts True Blues (12-5 Watt Chips)
120 Watts of Royal Blues (24 -5 watt chips)
30 Watts of Atinic 420-430 (30- 1 Watt chips)

I will probably back down on the Atinics initialy running 6 at 350 ma to see how it balances my color. I still have that fear they will push things pink on my like the prior near UV chips I used did.

I also do not want to pull the plastic lenses from them as they do act as UV protection and several expert claim that light under 400nm is more detrimental to corals than it is benificial.

[megadeth72]

I'm using 420nm violets, and they do make a big difference, I have one red acro that's green in my tank, in 2 weeks it's turned pink and still going

advancedaquarist has an article that details quite a few nm peaks that excite coral floresce and one of them is 420nm to excite 620nm and I think that's what's working on the acro I have

[Dave Thebrewguy]

So with my present lighting with my blues being at 454 nm and 460 nm the real spread is between about 444 and 470 nm. This leaves a gap between 420 nm and 444 nm I'd like to fill. Ideal in a perfect world a 432nm LED would be ideal for this.

I'm using a mix of 410-420nm violets and 440-450nm RBs (both from Steve's LEDs) to fill in this part of the spectrum. This is in addition to the usual 450-465nm XT-Es, 460-470nm blues, neutral and warm whites, all in a 1:1:1:1:1:1 mix and I had no sign of any "pinkness," just the opposite, I had too much blue. The 410-420nm violets peak at 417nm, not quite the 430nm you're looking for but certainly a helpful wavelength.

[zachts]

Rapid LED is winning my vote right now. I have yet to have one burn from them!

I have however burned up every other one available. Just got some new ones from Steve's though and they are much beter quality/brighter than the previous batch, they look blue'er when compared next to other violets. Also I'm assured these will not burn up at 700mA, but time will tell.

The ones from Rapid can easily handle up to 700mA

mcgyver if you keep posting banned sites you will get this tread closed and youself in trouble. personally I wish the filter would just say "CENSORED" and link to an explanation but that is not how it gets done its seems.

[TropTrea]

I'm using 420nm violets, and they do make a big difference, I have one red acro that's green in my tank, in 2 weeks it's turned pink and still going

advancedaquarist has an article that details quite a few nm peaks that excite coral floresce and one of them is 420nm to excite 620nm and I think that's what's working on the acro I have

I'm not sure if was advance awuarist or another site that ran a series of articles on florescense and photosynthesis in corals and there actual effective wave lenghts. I created a chart from these articles and have well over 100 chemicals listed. Of these roughly 60% requrire light between 430 nm and 460 nm to excite them. It goes up to roughly 90% between 420 nm and 510nm.

An interesting thing in my experiments I have an acro that under just neutral whites looks blue gray, under just 460nm blues looks bright yellow, and under just 454 royal blues looks bright green. But when they are all are on it picks up an extremely bright blue green look. There are probably at least 3 chemicals in this coral being excited by different frequencies and emotting light in anywhere from 3 to 6 different frequencies. The eye inturptes this light combination and interestingly everyones eye is not identical so it appears slightly different to different people as well.

[tomservo]

Dennis, be careful of which 420nm LEDs you buy, it seems some of the cheap ones have lenses that degrade under the intense near-UV. I've seen a few do this, ones from that snakey place are confirmed to do it if run fairly hard.

I recommend led fedy, they have 410-420nm and I believe also 420-430nm, but most importantly they have them available with 2 chips per star, so even driving them at 700ma is acceptable. Email their sales lady, Ava, and ask about the 420-430nm. The price is pretty competitive and I've been very happy with their product; no lens darkening to date.

That's cool about the coral; I've noticed this sort of thing, too.

[zachts]

Dennis, be careful of which 420nm LEDs you buy, it seems some of the cheap ones have lenses that degrade under the intense near-UV. I've seen a few do this, ones from that snakey place are confirmed to do it if run fairly hard.
they will probalby do this at lower currents, it'll just take a lot longer. a year instead of a few months perhaps. the damage is still taking place just much slower. I see the same thing happen with 5min. epoxy I've used to glue on lenses and attache acrylic splach sheilds. the epoxy on the inside that gets hit with violet turns brown. what's on the outside and doesn't get hit with violet light stays clear, for what that's worth.


I recommend led fedy, they have 410-420nm and I believe also 420-430nm, but most importantly they have them available with 2 chips per star, so even driving them at 700ma is acceptable. Email their sales lady, Ava, and ask about the 420-430nm. The price is pretty competitive and I've been very happy with their product; no lens darkening to date.

What current are you driving yours at and for how long have they been running, heatsink set up etc? thanks!

'side note' those two chip leds scare me a bit since they are almost always two 1 watt leds wired in parrelel. unless they have told you otherwise. the fact that they list output in lumens not mW makes me wonder also. you can't measure violets or royal blue in lumens. anyway, just my humble observation.

[Eud]

I'm planning to buy some of those two types of violets for my upcoming build. Apparently the problems with the browning on the little domes attached to the chips has been solved, and they now say that you can run at least the solderless ones which I think are a newer batch at 700mA without problems. That's what they say.

Also, they post spec sheets and I don't see much in the UV range for the higher of the two, so I wouldn't think you'd have to worry about the protection the lenses provide.

[zachts]

megadeth,

Also, they post spec sheets and I don't see much in the UV range for the higher of the two, so I wouldn't think you'd have to worry about the protection the lenses provide.

I'ts that little "not much" that causes the problem with the lenses degrading and turning brown. UVA radiation clasification starts at 400nm so any little bit of light below this threashold will defiantely have a degrading effect on non stable plastics. (see the circled areas on the attached graphs. it may only be a few percent of total output in this range but remember that it is very highly concentrated and the cummulative effect is therefore greater.

I would suspect that even the 400 - 410nm peak output of many violets also has this effect. as observed by the epoxy i use in many of my fixtures browning where exposed to light from the leds while remaining clear where it gets no LED light hitting it.

I like the look of that spectral graph for the 430s, if it is accurate I may have to give them another try. Has anyone compared one of the 405's with one of these 430's side by side to see if there is acctually a difference in color?

[megadeth72]

I run a glass lens anyway and mine do not have that little glob of plastic on them

Sent from my SCH-I535 using Tapatalk 2

[Eud]

megadeth72, this is off the OP's topic, but what lenses are you using? Seems every LED vendor has their own lens and most of them don't specify the maker of said lens or any optical characteristics other than which if their products it will fit on.

[megadeth72]

borite glass lens

http://www.geekopolis.com/Other/2012/i-RNb8tj6/0/M/IMG_0559-M.jpg

these are the 420nm's I use

http://spectralworkbench.org/analyze/spectrum/2590

[tomservo]

What current are you driving yours at and for how long have they been running, heatsink set up etc? thanks!

'side note' those two chip leds scare me a bit since they are almost always two 1 watt leds wired in parrelel. unless they have told you otherwise. the fact that they list output in lumens not mW makes me wonder also. you can't measure violets or royal blue in lumens. anyway, just my humble observation.

I made three similar fixtures using the fedy dual chips blues and in two fixtures, the pottery snake violets, and some from aquastyle. The ones from aquastyle and the serpent both have turned brown in ~6 months. If you're careful you can pop the lens off without damaging the chip and connects, and then cover with the appropriate type of silicone (alcohol cure electronics stuff like from ac-rc). These are all driven at 700ma.

The fedy dual chips ones are 3w emitters. They also do the same treatment to the 660 reds and some other colors as well. The nice thing is using the dual chips types, you don't have to worry about killing them running at 700ma on cheap drivers.

I've since moved to multichip arrays - my system now uses the old light over the frag tank, and that tank is growing algae. It's gotta be the neutral white emitter, since it's the same water in the system.

[vitz]

dana riddle is the one who wrote all of the great tech articles on light wavelengths, pigments, and photosynthesis y'all are referring to :)

[zachts]

I run a glass lens anyway and mine do not have that little glob of plastic on them

Indeed, I think those massive multi chip versions would bake my tanks! :)

for the rest of us I think the latest generation of smaller Silicone encapsulated Chips now being offered will solve the issue of burning. fingers crossed!!

[megadeth72]

why would it bake your tank? They have no more par than a 250w halide

this is a 50w hybrid on my sons 10g reef, can put anything under this light, from sps to low light zooanthids

he's got a few acans and softies in it right now

http://www.geekopolis.com/Other/2012/i-Tw6MRkq/0/L/IMG_1242-L.jpg

[TropTrea]

A couple of observations and notes.

Spectural work bench- This is a noice economical tool that is great for comparisons however true accuracy is very questionable. The problem is that every camera brand and even different automatic setting make the colors rendered slightly different. In the professional world of color evaluation there is a big difference in the accracy between $10,000 and $200,000 color spectrometers. The accuracy below 450 nm and above 660 nm is where the biggest difference in accuracy exists. Yes this is a good tool to compare light sources but determing if a peak is at 410 nm or 425 nm is very skeptical with this system. Determing that LED A peaks at a shorter wave lenght than LED B is about the tru level of it usefullkness. But if the spread of peakes in the near UV range is 5 nm or 15 nm is much more questionable.

The browning of the plastic mentioned by some and not by others is truly a natural reaction of most plastics to any UV light. This is why many items in you house will slowly turn yellow or even brown when exposed to sunlight. In reality glass is much better filter of UV light and is not as suspectable to browning or heat. There are plastics that can be treated to reduce the browning however what happens is they coat them with a UV filter which also creates more heat from the UV light.

On the 50 Watt light over the 10 Gallon tank the thing I first saw in the picture is the distance between the light ant the tank itself. I'd estimate the light is about 12" above the water surface. While this is good on a small tank like this to get a more even difference from the top to the bottom tank as far as quantity of light is concerned a much lower amount of wattage could yield an equivelent quantity of light on average at a lower distance. I'm running roughly 72 watts on a 40 gallon with great results having the LED's only 4" above the surface and absolutley no cooling other than allumnium channels for heat sinks.

Yes Riddle has written several articles on lighting that are great. But he is not the only one. I never make conclusions from just one individuals results without seeing simular results from others or my own experience. Even with experts there are many different opinions on many things and lighting is one with the most descrepencies even between experts. There are probably a dozen autors out there now that have written fantastic articles on lighting in the reef and Dana is one of the better sources of these articles.

[megadeth72]

I dont run them that close on any of my leds, otherwise there's hotspots, not really visible but they sure show up with the par meter

PS, I tested spectral workbench with all the leds that I have, and found it to be very very accurate, assuming my leds are not way off on what they are supposed to be, 420 peaked at 420, 450 was right, 455 was right, 655 was right

each setup is calibrated so it's not like a one size catch all, it's very ingenious how they do it

[TropTrea]

'side note' those two chip leds scare me a bit since they are almost always two 1 watt leds wired in parrelel. unless they have told you otherwise. the fact that they list output in lumens not mW makes me wonder also. you can't measure violets or royal blue in lumens. anyway, just my humble observation.

I would agree that if this is a two cip set on a single star then 700nm could very well indicate these are 1 watt chips. It they are wired in parrellel then they are getting 350 nm each. most chips at 350 mw will run at between 2.5 and 2.8 volts. This maens each chip is running between .874 and 980 mw.

As far as measuring lumns instead of mw though I both agree and disagree with you here. Lumns is the sum of light emitted as seen by the human eye. It includes all light between 380nm and 700nm but is heavily wheighted for light above 430nm and most sensative to light at 555nm which the human eye is most sensative to. As far as the mW rating is concerned it does not adjust for the entire spectrum but more or less reflects a peak amount of light regardless of what frequency it is at. Considering we are talking light sources with peaks below 430 nm the mW rating would be much higher than the lumens rating. If you could compoare the two together you could almost say it is like creating a ratio between total light / visable light. The larger this ratio is the more light your eye will pick up, and the smaller this ratio the more light is concentrated into wavelenghts that that eye is either not or less sensative to.

You cn take a light source at 280nm out of the range of the human eye and should have a lumnes of 0 whale the mw rating can be very high. Simularly a light source at 555nm Coulkd have an extremly high lumnes as well as mW rating since all it light is at the most sensative part of the human eye.

I do agree that it makes much more sense when you rating any narrow bandwidth lighting source in mW than is Lumnens. If your interested in a naroow band width you want to know the energy at that band width ragardless of its effect on the human eye.

[TropTrea]

I dont run them that close on any of my leds, otherwise there's hotspots, not really visible but they sure show up with the par meter

PS, I tested spectral workbench with all the leds that I have, and found it to be very very accurate, assuming my leds are not way off on what they are supposed to be, 420 peaked at 420, 450 was right, 455 was right, 655 was right

each setup is calibrated so it's not like a one size catch all, it's very ingenious how they do it

The issue I see that cmera lens basicly all have a UV filter built into them. This UV filter is designed to protect the sensors in digital cameras and to prevent the influence of light outside the human eye range on film cameras. hese UV filters varry but all will be close to 100% effecient at 380nm and will start filtering the light below someplace between 460nm and 420 nm. So the shorter the wave lenght under 460 nm the less I would trust any program using a standard camera and photo lens. Yes it may show the peak at the right or close to the right wavelenght but at a short enough wavelenght it will not be able to pick anything up.

The light spectrum anylizers I had worked with years ago had multiople sensors that were each calibrated for a specific wave lenght of sensativity. Basicly the more sensors and the wider the band width it measure the more expensive it was. An example a lower cost model might run between 460nm and 660 nm with a sensor every 5nm apart for a total of 40 sensors, While a top of the line modle would be sensative from 360nm to 720 nm and have only a 2nm difference between sensors for a total of 180 sensors.

Then there the special units to check UV emissions that ran from 280nm to 460 nm. Light bulbs were spot checked on these to assure that less than 0.1% of radiation was emmitted below 380nm compared to the range between 420 nm and 460 nm.

[megadeth72]

The issue I see that cmera lens basicly all have a UV filter built into them. This UV filter is designed to protect the sensors in digital cameras and to prevent the influence of light outside the human eye range on film cameras. hese UV filters varry but all will be close to 100% effecient at 380nm and will start filtering the light below someplace between 460nm and 420 nm. So the shorter the wave lenght under 460 nm the less I would trust any program using a standard camera and photo lens. Yes it may show the peak at the right or close to the right wavelenght but at a short enough wavelenght it will not be able to pick anything up.

The light spectrum anylizers I had worked with years ago had multiople sensors that were each calibrated for a specific wave lenght of sensativity. Basicly the more sensors and the wider the band width it measure the more expensive it was. An example a lower cost model might run between 460nm and 660 nm with a sensor every 5nm apart for a total of 40 sensors, While a top of the line modle would be sensative from 360nm to 720 nm and have only a 2nm difference between sensors for a total of 180 sensors.

Then there the special units to check UV emissions that ran from 280nm to 460 nm. Light bulbs were spot checked on these to assure that less than 0.1% of radiation was emmitted below 380nm compared to the range between 420 nm and 460 nm.

step 1, remove UV filter then go to step 2, seriously that's how the directions read

I have no interest in light below 400 anyway, my halides had uv shields too

technology is moving fast, here's my 450 and 420 spectrum tests on a couple of leds I have

http://spectralworkbench.org/analyze/spectrum/2590
http://spectralworkbench.org/analyze/spectrum/2589

[zachts]

As far as measuring lumns instead of mw though I both agree and disagree with you here. Lumns is the sum of light emitted as seen by the human eye. It includes all light between 380nm and 700nm but is heavily wheighted for light above 430nm and most sensative to light at 555nm which the human eye is most sensative to. As far as the mW rating is concerned it does not adjust for the entire spectrum but more or less reflects a peak amount of light regardless of what frequency it is at. Considering we are talking light sources with peaks below 430 nm the mW rating would be much higher than the lumens rating. If you could compoare the two together you could almost say it is like creating a ratio between total light / visable light. The larger this ratio is the more light your eye will pick up, and the smaller this ratio the more light is concentrated into wavelenghts that that eye is either not or less sensative to.

You cn take a light source at 280nm out of the range of the human eye and should have a lumnes of 0 whale the mw rating can be very high. Simularly a light source at 555nm Coulkd have an extremly high lumnes as well as mW rating since all it light is at the most sensative part of the human eye.

I do agree that it makes much more sense when you rating any narrow bandwidth lighting source in mW than is Lumnens. If your interested in a naroow band width you want to know the energy at that band width ragardless of its effect on the human eye.

I always refur to mW since as you mentioned that 0 lumen 280nm source might well be cranking out 1000mW and you'd be blind before you even realized it was on!

so I always look only at peak wavelenth and mW for comparing violet and blue LEDs. the ideal violet peaks around 420 and has the highest mW rating for the lowest current and voltage input.

At least thats my logic :)

[TropTrea]

step 1, remove UV filter then go to step 2, seriously that's how the directions read

I have no interest in light below 400 anyway, my halides had uv shields too

technology is moving fast, here's my 450 and 420 spectrum tests on a couple of leds I have

http://spectralworkbench.org/analyze/spectrum/2590
http://spectralworkbench.org/analyze/spectrum/2589

There is only one big thing about step one. That is most of the higher quality camera lenses now have a UV filter built right into them. This is especialy true of digital cameras.

Then there is the fact that when UV filters are filtering out all light at say 380nm they are still filterout 80% to 95% of light at 400nm and probably 20% to 45% at 420 nm.

On a side note I have just tried the newest "UV" LEd;s from Rapid. These are suposedly 430nm LED's and I realy love them. They do not turn my tanks pink like the old ones used to.

[zachts]

When did Rapid start carrying 430nm? all I see are the 410-420nm. I only know of one place carrying supposed 430nm and I've not been real thrilled with violets from that source.

[TropTrea]

YEs it was my mistake the new C's from rapid are rated at 410-420 by Rapid it is the old ones that rated at 430nm, Interestingly the 430 produced more of a violet (pink) tint than the newer ones from Rapid.

However I realy do not trust nm rating on chips in this near UV range. I have seen several spectrum analysis posted on Reef Centeral that compared different "UV" spectrums and found that in comparisons to each other some of the vendor chips were not what they said they were if others were.

One particular comparison I saw looked at a 430 nm chip compared to a 410 nm chip but showec that the peak of the 430 nm chip was actualy slightly shorter than that of the 410 nm chip. I'm not crazy about the accuracy of the accuracy of reading exact wavelenghts of the camera based spectrum accuracy to determin accurate nm numbers but I do think they are accurate to determine which are peaking at a higher or lower wave lenght. With manufacturer specs on might be working on a +- 2% accuracy and another might be working on a 5% accuracy. If Johnny rats hi chip at 415 nm with a 2% accuracy the tru peak could be between 406 and 423 while another might rate there 430 nm chip at 5% accuracy meaning they are between 408nm and 451 nm.

Even within a manufacture you can find different ratinings dependent on how you order your chips. An example would be CREE XT-E RB that could range from 446 nm to 470 nm but if you ordered that chip by bin number D-46 you would have something between 454 and 456 nm. Very few vendors of star mounted LED's though do allow ordering by specific bin numbers.

[sfsuphysics]

One thing I notice about the Rapid UVs, and I might be crazy for thinking this, is that it has a slighly green tint about it, not sure if it's just exciting particulate matter in the water column or what not...

Either way though, they do cause a different fluorescence than say royal blues, so it's all good :D

[TropTrea]

One thing I notice about the Rapid UVs, and I might be crazy for thinking this, is that it has a slighly green tint about it, not sure if it's just exciting particulate matter in the water column or what not...

Either way though, they do cause a different fluorescence than say royal blues, so it's all good :D

Ate you talking about the older or new Rapid UV's. I had the earlier ones and I hated the amount of link it pumped into my tank. The newer ones I just tried last week looked much closer the color of the 454 Royal Blues. just a slight amount of more violet and visualy not as intense. The true otput may be equal but the eye does not pick up the shorter wavelenght as well.

If I recall it is 380nm that hits the point of being actually invisable to most human eyes and that is why we see the shorter wave lenghts as being much dimmer.

[sfsuphysics]

Ate you talking about the older or new Rapid UV's. I had the earlier ones and I hated the amount of link it pumped into my tank. The newer ones I just tried last week looked much closer the color of the 454 Royal Blues. just a slight amount of more violet and visualy not as intense. The true otput may be equal but the eye does not pick up the shorter wavelenght as well.
Well I'm not sure if they're older or newer, they're ones I picked up maybe a month ago, solderless ones too, they could be older stock. However I will say that there is absolutely no pink in them at all. And yeah they don't look terribly bright at all, in fact unless you look at them dead on they barely look like they're getting any current (however I did check and I am pushing them at 600mA.



If I recall it is 380nm that hits the point of being actually invisable to most human eyes and that is why we see the shorter wave lenghts as being much dimmer.
It's more to do with the sensitivity of the cones in our color vision.

Our color vision has 3 ranges of sensitivity, the overlap of two types is why green and yellow looks so bright to us.
http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/540px-Cone-fundamentals-with-srgb-spectrum.svg.png

You can see the relative intensity that our eyes pick up with this graph though, and yeah 430nm we see it as maybe 3% that of green light
http://upload.wikimedia.org/wikipedia/commons/e/e9/Eyesensitivity.png

And there's the lesson for the day :D

[TropTrea]

Yes I'm very aware that cones in our eyes are most sensitive at
The blue Cones are sensative to light from 380 nm to 540 nm with a peak sensativity at 445 nm
The green cones are sensative from roughly 400 nm to 660 nm with a peak sensativity at 535nm
The Red Cones are sensative from roughly 420 to 700nm with a peak sensativity at 570nm.
Then there are rods which are sensative to light from 380 nm to roughly 550 nm.

We normaly conceive true blue light in the range of 560 to 570 nm. As the eye and brain combines the messages from all three cones and the rods we actually interpulate the data. But every individuals can unperpulate that data slightly differently. As the actual wave lenght of the light goes below 460 to 454 nm we rename this light royal blue as it is not the true blue we considered for the 460nm light. Simularly when the wavelenghts becomes even shorter we call it ultra violet.

Now what confuses people is if we look at paint pigments. We can take the truest blue paint on the market to the eye that only reflects light at 460 nm. Then we can start adding some red pigment to it that only reflects light at 670 nm that would look the brightest purist red to most people. As we do this the eye sees a combination of the 460 and 670 and interpulates it as some ratio between red and blue which we call purple or violet.

The real question is why do people some people see light at 410 nm as being violet rather than a deeper blue. The theory is that eye picks up the level with the blue cones and the more sensative rods but is missing any appreciable data from the green and red cones. Therefore it tricks the brain into filling in that missing red data, which realy never existed. The other theory is that what we preceive as true blue is not truely pure blue but a combination of blue and the green and red since both the red and green cones are also very slighly sensative to light at 460 nm.

Another interesting think is when I had several ov the earlier designed near UV leds over my tank some people said it looked pink. While others did not see the pinkness but described it as a very dark blue. My only explaination to this is the difference in sensativity between individuals eyes to the light at these shorter wavelenghts. These same people that call it pink do not quickly recognize the differences between different shades of red and red orange.