Hypothesis: Wavelength limit perception correlation

[CurtisOliver]

So a question popped up on another site about colours some population can see properly and others can't. Well this sparked me revisiting this subject. We all know from previous discussions that some perceive wavelength limits differently from one another. However this usually appears as two clear groups for each side of the visible spectrum. Listed below are the groups and characteristics.

** Important: In order to have accurate results please read this post first and each poll category carefully before submitting. And you must have first-hand experience of handling both <420nm and >700nm wavelengths. **

Group 1: Those that can see near-IR
Group 2: Those that cannot see near-IR
Some report being able to see reasonably far into the near-IR spectrum whilst others can't. By this, I am using 800nm as a threshold.

CHECK: If you cannot see beyond 800nm clearly (for example, it must appear as dim red rather than desaturated red or grey) then you fall under not seeing Near-IR very well. A fair test is to use a cheap Chinese non-IR filtered 532nm DPSS pointer. You should be able to detect a red spot at these power levels. DO NOT SHINE LASER IN EYES! If you can perceive 808nm and even >850nm then you have good Near-IR vision. If you happened to be able to check using alternatively higher wavelengths, let me know my commenting on this thread.

Group 1: Those that can perceive near-UV clearly and can see further into the UV spectrum
Group 2: Those that cannot perceive near-UV clearly and cannot see further into the UV spectrum
Some report spot blurring when observing near-UV and <420nm wavelengths. And some can see further into the UV spectrum.

CHECK: If you cannot see <420nm clearly (for example, lack of colour differentiation between violet wavelengths, lacking ability to focus on the spot, spot appear blurry and has excessive halo, seeing blue rather than violet at <385nm) then you fall under not seeing Near-UV very well. If you can differentiate shades of violet, can see a sharp spot like other wavelengths and have the ability to perceive <370nm then you have good Near-UV vision. A fair test is to use a 405nm pointer. Aim it 30cm away and again at >1m. Can you focus on the dot? Make sure you observe on a surface that doesn't fluoresce (black surface). Again, if you happened to be able to check using alternatively lower wavelengths, let me know my commenting on this thread.

I have proposed in the past that there is a correlation in those that can perceive further into the near-IR part of the spectrum and those that cannot see near-UV very well and vice versa.

So I am proposing a poll for a quick research project to determine if this correlation stands.

What I want to know is whether there are some extraordinary individuals that can actually see both ends of the spectrum well in accordance to the factors mentioned above. Also it will be handy to know if some can't see either end clearly. If you can't, is there any medical factors involved?

But of course, I want to determine whether people see one or the other.

The poll options are simple:

Poll Options:

• I can see Near-IR (>800nm) clearly AND I can see Near-UV (<420nm, non-blurry spot) clearly
• I cannot see Near-IR (>800nm) clearly AND I cannot see Near-UV (<420nm, non-blurry spot) clearly
• I can see Near-IR (>800nm) clearly BUT I cannot see Near-UV (<420nm, non-blurry spot) clearly
• I cannot see Near-IR (>800nm) clearly BUT I can see Near-UV (<420nm, non-blurry spot) clearly

I appreciate any response to this. If anyone has any queries or suggestions, fire away.
It will be interesting to know the outcome.

 

[Unown (WILD)]

I gotta do a test for both now that I'm curious. I do tend to see UV better but I haven't actually tested the two. Any diode suggestions to purchase for testing?

 

[CurtisOliver]

I stuck with easy wavelengths such as a 405nm and 808nm to make this more accessible. But those with <400nm diodes and >850nm would further validate their claims. For most part, those wavelengths mentioned will answer those tests based on the factors mentioned.

Your result should be changeable if you find anything different.

 

[ZRaffleticket]

Hm. I get the intent but think the uv side of the spectrums choices need better wording, let me explain: Blurriness has to do with the focus of the lens in your eye. You can observe the halo blur around 405nm change if you aim the spot far away, but focus your eyes on something close to you. I think whether you see a blur or not is going to come down to near/far sightedness. However, the rest of the post suggests how well you can perceive the wavelength, if at all, so that's how I'll answer.

Also, one thing to bear in mind about the shorter wavelengths is that you also have to deal with material fluorescence, which often gives a gray tinge that doesn't actually exist in the wavelength on its own. Make sure you're aiming at something that does not fluoresce at all, such as metal (away from you!) It can be black anodized, polished, unpolished... honestly there are not many materials that don't fluoresce under high energy photons.

If you want raw data, this is what I can share:
1064nm - cannot see at all
940nm - appears red, however this is incredibly dim and I can only see it in complete darkness
808nm - appears red, extremely dim, but I can make out a spot with indoor lighting at ~500mW
410nm - blurry violet, but plenty visible
405nm - blurry violet, not perceptively less visible than 410nm
395nm - blurry violet, noticeably dimmer than 405nm but I wouldn't call it dim
375nm - blurry violet, pretty dim at 250mW, though appears just as bright as a <5mW 405nm pointer I have that doesn't read on my LPM
355nm - blurry blue (yes blue, not violet!), extremely dim, would almost never notice without material fluorescence, however you can see the beam due to how fluorescent dust is

 

[CurtisOliver]

Hm. I get the intent but think the uv side of the spectrums choices need better wording, let me explain: Blurriness has to do with the focus of the lens in your eye. You can observe the halo blur around 405nm change if you aim the spot far away, but focus your eyes on something close to you. I think whether you see a blur or not is going to come down to near/far sightedness. However, the rest of the post suggests how well you can perceive the wavelength, if at all, so that's how I'll answer.

Also, one thing to bear in mind about the shorter wavelengths is that you also have to deal with material fluorescence, which often gives a gray tinge that doesn't actually exist in the wavelength on its own. Make sure you're aiming at something that does not fluoresce at all, such as metal (away from you!) It can be black anodized, polished, unpolished... honestly there are not many materials that don't fluoresce under high energy photons.

If you want raw data, this is what I can share:
1064nm - cannot see at all
940nm - appears red, however this is incredibly dim and I can only see it in complete darkness
808nm - appears red, extremely dim, but I can make out a spot with indoor lighting at ~500mW
410nm - blurry violet, but plenty visible
405nm - blurry violet, not perceptively less visible than 410nm
395nm - blurry violet, noticeably dimmer than 405nm but I wouldn't call it dim
375nm - blurry violet, pretty dim at 250mW, though appears just as bright as a <5mW 405nm pointer I have that doesn't read on my LPM
355nm - blurry blue (yes blue, not violet!), extremely dim, would almost never notice without material fluorescence, however you can see the beam due to how fluorescent dust is

Based on what you’ve outlined Z, you fall in the same category as me. Can see near IR but not near UV properly so will need to change your vote. A reminder to everyone that when it comes to near UV that it isn’t just a case of being able to see it. It’s how we see it. Some people are able to focus properly on shorter wavelengths without the blur. The blur isn’t to do with near/far sightedness as I have normal vision myself. The effect only becomes apparent as I verge towards the violet-blue end of the spectrum. Halo is a better word rather than bloom. That’s what I was trying to say. As for fluorescence that’s mentioned in red and bold.

Thanks for the reply as it will help iron out problems early on.

 

[bostjan]

980 nm LEDs appear invisible to me. 940 nm LEDs appear extremely dim. 850 nm LEDs, to me, are just like regular red LEDs, but less intensely bright. My 808 nm lasers are perfectly visible, even at low power.

On the other end of the spectrum, I have some UV LEDs, but they are rather high intensity. 350 nm, 365 nm, whatever, even secondary reflections are grey and blurry and unmistakable to me.

 

[CurtisOliver]

It’s quite cool that you’ve managed to observe as high as 940nm in your tests. What will be interesting is where your end point is. Somewhere between 940 and 980nm you will start to observe grey light.

 

[julianthedragon]

I have not participated yet because I don't have a near-UV or near-IR light source close enough to check.
However, I wanted to share 2 articles about something called "two-photon chromophore isomerization" or "two-photon absorption":

https://www.pnas.org/doi/10.1073/pnas.1410162111

https://cen.acs.org/articles/92/i49/Humans-See-IR-Light-Photons.html

It's a phenomenon I remember some members talking about firsthand in the past although I can't find the thread.
But nonetheless it enables some people to see IR light at half its wavelength, ending up somewhere in the blue-greens.

Quote from article 2:
"The subjects perceived wavelengths longer than 950 nm to have a color that matches a wavelength slightly longer than half the original IR—a greenish hue. This phenomenon, the team concluded, could be caused by either of two optical phenomena: second-harmonic generation or two-photon absorption."

 

[CurtisOliver]

Yes, two photon absorption in our own eyeballs has always fascinated me. Grey light is also another phenomena that interests me too. We are capable of seeing so few photons that we can trigger our rods but not our cones in our eyes.