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Comment by FergusN | Hacker News Reader

Fun fact - Some humans can see UV light. People that have had their lenses removed, normally due to having cateracts surgically removed. I know this because i had my lenses removed at 3 months old and have worn contact lenses my enitre life. The first time i became aware i could see UV light was in a bowling alley with black lights, where one of my contact lenses had uv filtering and the other did not. A very disorienting experience. This is my very low-key superpower.

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Fellow aphakic here, can confirm. I never knew what people were talking about when they said blacklights, they just look like a real bright intense pinkish/purple light.

I only realised one day when I noticed that some kinds of lights looked really dark through my glasses but really bright when I took them off.

No, what you and OP are noticing is the overlap of the UV filtering and near UV visible range with your lenses.

Maybe I'm misunderstanding, but is that not what they are saying?

They aren't seeing UV, they are seeing the near UV that that the UV filter overlaps with.

If UV lights look like normal pink or white lights to you, then you can see that spectrum.

Ok, but for people with normal vision: when you look directly at a UV bulb, are you “supposed” to see an intense (brighter than any object fluorescing under the bulb) purply color that is hard to bring into sharp focus, or does it just look like a bulb that is switched off / totally dark?

They look deep purple to normal eyes, if they look bright pink/white you can see UV

Yes.

It depends on the bulb. “Black light” used to mean a very specific fluorescent tube tech with a specific wavelength output, but now there are all sorts of different methods and wavelengths out there and each of them looks different to the eye (average vision and I’m assuming those with UV vision also).

UV LEDs are the worst offenders for this as their spectrum can be all over the place even due to QC-passing manufacturing defects.

I have been curious in the past about how much of it is that effect (ie- how much further away from the ‘visible’ UV spectrum I can actually see). It’d be interesting to know.

I found some experimental data from other people with aphakia:

https://sci-hub.se/https://doi.org/10.1016/0042-6989(92)9016... ("Scotopic spectral sensitivity of phakic and aphakic observers extending into the near ultraviolet")

It looks like it's basically the entire ~315-420nm range. And, we normal/phakic people are technically sensitive to all of those wavelengths too—they're just very heavily, not completely, attenuated by lens absorption. Your relative sensitivity is greater by a factor of maybe 10,000, at 350 nm.

I can also see black light as deep purple, but I never had eye surgery. I think this due to the fact that spectra of UV lights spread into the visible range as well, but the peak emission is at UV-A.

For me they’re like a whitish-purple (intensely purple) but bright like any other regular light. About as bright or only slightly dimmer than the objects that glow from them.

Stupid question probably: does sunlight on days where there are high UV radiation warnings (announced so people know to not stay in the sun too long and avoid sunburns) look any different to you?

Do you know what part of the UV spectrum you can see?

Edit: hmm, and the article's abstract says that reindeer' eye fluid is 60% transparent to UV (I assume that means "60% at the average thickness/depth of a reindeer eye from lens to retina"). That sounds like other animals' generally does not. Does humans'? I guess it must if you're seeing it, or you have special eye fluid!

No stupid questions. This is not something i have noticed before. I don't think I am able to discern the difference to be honest. The sun during the day just looks like white, yellowish light to me.

Is there a way to compare what you see with what the average person sees? Would a “calibrated” photograph of a sunny day let you “see” what people see when they have “normal” vision?

I thought most humans could? I can definitely discern UV light from other sources. What does it look like to you? Very curious. A white shirt, white teeth etc dawn a very bizarre bright appearance under UV light. Tennis balls too.

Those things you mention are fluorescent. They reemit UV light at different frequencies. Anyone with normal vision sees that.

Yeah so for someone who can “see” uv light what does that mean? No one can see light we only see the reflection off surfaces.

The way to distinguish it is to look directly at the UV light "bulb".

If you can see that unreflected light you have very unusual sight powers.

I don't now if this is even possible, but someone up thread claims they can do it.

If you have a UV light and look at the bulb or LED, you don't see any light coming from it at all? The bulb just looks to you like it isn't on?

UV bulbs look bright purple to me. They are so intense, I can barely even look at them directly. I always thought they were called black lights because they do not appear to light up a room (excepting materials that fluoresce under UV light); the UV light itself is very bright, but everything else stays almost as black as if there were no light at all.

I don't think I can see UV light, though. I don't see UV patterns on flowers that have them, for example. I think I am just seeing some violet light that UV bulbs also release, and maybe it feels so bright because the invisible UV stings my eyes.

Everyone can see that. Those old “black light” fluorescent tubes had filters that eliminated most of the visible light and appeared a dim purple when on… but modern UV LEDs and such emit plenty of visible light.

> UV bulbs look bright purple to me.

That's because they emit a bit of violet light too

> maybe it feels so bright because the invisible UV stings my eyes.

Afaik the problem with UV is that your eyes don't feel them immediately, the pain comes hours later

Fluorescent things shift frequencies, normal light reflection does not. You wouldn’t see any UV light in a dark room unless it struck something fluorescent. Plenty of things are not at all fluorescent.

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