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Comment by Fr0styMatt88 | Hacker News Reader

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.

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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.

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

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.

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?

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.

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

Yes.

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