Testing IR Sensitivity: My Experiment

[DaveC426913]

I learned https://www.physicsforums.com/showthread.php?p=1098513&posted=1#post1098513" that some people are sensitive to lower frequency light than others. In fact, some people can see well into the infrared range.

I was very skeptical, so I tested it out. I was right, I cannot see IR. However, to my astonishment, my son can!

Here is my experiment, which I encourage you to try. I'd love to know.

1] Get really dark - throw a heavy blanket over your head or go into a dark room.
2] Point your remote at your face. Press some buttons. Note if you see the red light or not.
3] (the enhanced-assisted version) To ensure you're not fooling yourself - have someone else press the buttons so you can't anticipate on-ness or off-ity.

 

[JasonRox]

I shall try that out one day.

I doubt I can see it though.

 

[moose]

I can't, I've tried before...although it wasnt a perfectly dark environment...

 

[Gokul43201]

Do all remote controls use the same LED? A 50 nm shift in the emission spectrum can make the difference between "Eureka, I see it!" and "Ugh, can't see squat!"

 

[Rach3]

If it's too dim, try pointing a 50W infrared laser directly into your eye. You might be able to detect that.

 

[DaveC426913]

Do all remote controls use the same LED? A 50 nm shift in the emission spectrum can make the difference between "Eureka, I see it!" and "Ugh, can't see squat!"

Yeah. this is the big flaw in my experiment.

However, I have demonstrated to my satisfaction that the phenom is real since my own experimentation used the same remote. Of four people in my house, three could not see it, while one could.

 

[Rach3]

Quick google search came up with the GaAs led at 940nm. Visible seems to end around 700nm.

See also:
http://en.wikipedia.org/wiki/Image:Cone-response.png

 

[Rach3]

Of four people in my house, three could not see it, while one could.

How sure are you? Are there any other (visible) lights on the remote? Was the experiment controlled against dishonesty?

 

[gravenewworld]

of course I can

 

[scott1]

I don't think I can. I tried an experment in my bathroom and I couldn't see anything but there was some light comming form the door, so I might try again in my garge.

I wonder if it's possible to get to train your eyes to see infrared(It just would be cool to se infrared light)?

 

[NoTime]

Do all remote controls use the same LED? A 50 nm shift in the emission spectrum can make the difference between "Eureka, I see it!" and "Ugh, can't see squat!"

Some are fairly bright, and can be seen in dim lighting.
Others are extremely dim and it has to be dark to see them.
Don't know if it's power or wavelength that makes the difference. Perhaps both.

The one out of 10 I can't see probaby has almost dead batteries, since its gotten real picky about pointing.
Maybe I'll find some new ones and try it again.

 

[NoTime]

I was very skeptical, so I tested it out. I was right, I cannot see IR. However, to my astonishment, my son can!

Well that's one

 

[DaveC426913]

How sure are you? Are there any other (visible) lights on the remote? Was the experiment controlled against dishonesty?

I made sure. I did the experiment a second time after ensuring I'd controlled it specifically against dishonesty.

No other visible lights.
I ensured it was pitch dark.
I held the remote and pressed the button rapidly and randomly.

Every time, he immediately said 'on' or 'off' - he didn't even have the decency to be hesitant . He got it right no matter how many times I tried it or how fast I did it. In fact, we went under the blanket together and I did the experiment. He still got it right every time, and yet I could see nothing. Once we took the blanket off, he showed me where the LED was situated within the little window.

 

[Math Is Hard]

I definitely see it. It is faint, but clearly there.

 

[Math Is Hard]

must be my vitamin A supplements:
http://www.mindhacks.com/blog/2005/08/changing_diet_might_.html

 

[Danger]

Totally expecting failure, I took the remote for the TV into the bathroom just now and the damned thing was bright as day (okay, not quite). W asked me what I was doing, so I pointed it at her and asked if she could see the light. This was in the living room with the TV, the kitchen light, and the neighbourhood lights coming through the balcony doors. She saw it fine, so I turned it around and saw it quite plainly even in that ambient light.
MUTANTS, UNITE!

 

[DaveC426913]

must be my vitamin A supplements:
http://www.mindhacks.com/blog/2005/08/changing_diet_might_.html

Cool. I wonder how hard it is to get hold of some retinal.

 

[Chaos' lil bro Order]

One of my remotes has a red 'signal on' light that goes on in addition to the IR emittin bulb. I could see this 'signal on' light in the back ground of the IR bulb, so I say beware of your remote and double check it. My other remote had no 'signal on' light and I could see the IR in light out conditions.

Dave, I suggest blacking out your kitchen, turning on your stove element, standing beside your son and seeing the difference in your IR threshold. Your son would beat you by a few seconds I'd guess. If you were especially into it, you could get a hold of your stove's specs and derive a solution for how long a second of delayed observation equals in terms of element temperature and finally of the wavelength emitted.

I think my element goes from 0 to 10 (max) in about 90 seconds. At 10 the element appears to be a orangy-red (more orange than red). I'm guessing its temperature at 10 is ~800C. At a setting of 0 (off), the element is roughly room temperature 20C. I'm not sure what material it is which would be critical to calucating its heating curve.

Anyways, just a thought.

 

[DaveC426913]

One of my remotes has a red 'signal on' light that goes on in addition to the IR emittin bulb. I could see this 'signal on' light in the back ground of the IR bulb, so I say beware of your remote and double check it. My other remote had no 'signal on' light and I could see the IR in light out conditions.

Yup. Same here. I used the non-cheating one.

Dave, I suggest blacking out your kitchen, turning on your stove element, standing beside your son and seeing the difference in your IR threshold. Your son would beat you by a few seconds I'd guess. If you were especially into it, you could get a hold of your stove's specs and derive a solution for how long a second of delayed observation equals in terms of element temperature and finally of the wavelength emitted.

Yeah that's a pretty iffy way of doing it though. Very prone to "overanticipation" and even "cheating". I also doubt it would be slow enough to observe much difference between us that wouldn't be swamped by reaction and perception times.

If he says "now" and I sat "now" two seconds apart, is that pretty much the same time or is that a significant difference?

 

[zoobyshoe]

Yeah that's a pretty iffy way of doing it though. Very prone to "overanticipation" and even "cheating". I also doubt it would be slow enough to observe much difference between us that wouldn't be swamped by reaction and perception times.

If he says "now" and I sat "now" two seconds apart, is that pretty much the same time or is that a significant difference?

Just for the hell of it, try having your son adjust the heat control to the point where the light first becomes visible to him. Mark it. Then, do this yourself, and see if there is any noticable difference between the marks.

 

[NoTime]

Stove controllers tend to have a very large hysterisis.
It would be very dificult to control for any selected point at best.

 

[Rach3]

Too many variables. Blackbodies emit at all frequencies - in essence you'd only be finding out who can see the dimmest red (visible) light.

Minor complaint - all visible light is visible; infrared radiation is invisible by its defintion. There is no "cutoff wavelength" or anything. If however, you can see all the way down to 10-micron light, then that's very different; then you have career potential as a spectrometer.

 

[Yonoz]

Just for the hell of it, try having your son adjust the heat control to the point where the light first becomes visible to him. Mark it. Then, do this yourself, and see if there is any noticable difference between the marks.

In all ovens I've seen the heating body is either turned on full power or off, according to the thermostat's setting and temperature. I'm not sure your suggestion would work, as with the door open any set temperature will have the heating body powered on indefinitely.

 

[zoobyshoe]

In all ovens I've seen the heating body is either turned on full power or off, according to the thermostat's setting and temperature. I'm not sure your suggestion would work, as with the door open any set temperature will have the heating body powered on indefinitely.

Not the oven element, the stove elements. These definitely are variable. You can set them to anything from low, slow simmer to fast boil.

 

[DaveC426913]

Stove controllers tend to have a very large hysterisis.
It would be very dificult to control for any selected point at best.

I have known a few stove controllers, and frankly, they are pretty even-tempered.

 

[Corkie2003]

I've been disappointed with an infrared night vision scope I bought. I turned it on, turned on the illuminator and though 'there's no way in hell the creatures out there can't see this' because I could not only see the dim red glow of the illuminator, but also the beam it projected.

Even though the illuminator was a 450mw one, the spectral range should have been out of range of my cones.

Yep, Mutants of the world unite!

 

[Yonoz]

Not the oven element, the stove elements. These definitely are variable. You can set them to anything from low, slow simmer to fast boil.

Oh you mean those electric plates... Silly me.

 

[DaveC426913]

Oh you mean those electric plates... Silly me.

Coils is the word you're looking for.
http://www.istockphoto.com/file_thumbview_approve/253947/2/Don_t_Touch_.jpg

 

[unitone101]

My girlfriend can see in IR. I've seen her use our remote as a flashlight, which completely dumbfounded me. She had always tought everybody could see the 'little light' coming out of the remote. She claims that people and warm objects are contrasted in the dark and still won't believe me when I say that for me it isn't so. My cup of coffee is NOT easier to see than a glass of water in a dark room for me but apparently it is for her.

She does seem to have problems with cold colors which make me wonder if she isn't living the phenomen which is reproducted with these googles

 

[DaveC426913]

She had always tought everybody could see the 'little light' coming out of the remote. She claims that people and warm objects are contrasted in the dark and still won't believe me when I say that for me it isn't so. My cup of coffee is NOT easier to see than a glass of water in a dark room for me but apparently it is for her.

That is awesome and creepy rolled into one.

Let's grind her up to a powder and sell her by the vial as an unction for super-vision.

 

[Proton Soup]

some women are tetrachromatic, so i wouldn't be surprised if more of them can see a bit into the IR or UV range.

 

[brewnog]

Weirdos, the lot of you.

 

[DaveC426913]

some women are tetrachromatic, so i wouldn't be surprised if more of them can see a bit into the IR or UV range.

Yeah, although I'm not sure it works that way. The extra photoreceptor works in the within the customary range, not outside it.

"...two types of red cones that are sensitive to slightly different ranges of the red end of the color spectrum. You would not be able to see extra colors the rest of us can’t (sadly, no ultraviolet vision, etc.), but you would be able to make distinctions between very similar colors that the rest of us cannot..."
http://www.blogadilla.com/tag/research/

 

[mgb_phys]

IR leds at 880nm have a bandwidth of at least 50nm as you under or over drive them the bandwidth and peak wavelength can move.
More importantly a dark adapted eye in a totally dark room can see individual photons! You can be a long way down the Gaussian wavelength profile of bright IR LED and get individual visible red photons

 

[~christina~]

I can! It's dim but basically, I have to look to the side of the remote, and my peripheral vision can spot it. I tried this with three remotes and 2/3 had visible red lights showing up, when I hit the buttons. It would blink and etc, depending on how much I pressed the remote buttons. Not sure why I can't see the light on one of them.

My chem lab instructor once asked me whether I could see IR, and I said, "yes.."
Then they proceeded to ask me if I was a bug.

Now I can say, "yes I AM"!

I was just wondering, why does trying to focus in a semi-dark room cause me to start having a sort of, "blackout" of the light in the room? (starts to look as if someone is starting to pour black paint into my vision= same as if what I'd see if I close my eyes)
note: semi-darkness= a crack of light in the room

Is it normal? This sort of made it hard to see the IR light of the remote because I had to unfocus from trying to see it, or I would basically have this, "blackout" of the light in the room, including the IR light itself. hm...

 

[Corkie2003]

Count me in.

I sell I.R. kit for outdoor sports, and the only way I know the illuminators are turned off, is by pushing the offer/onner so the little LED goes out and THEN checking at the business end to make sure the lights are indeed turned off.

This applies to I.R. lasers (which I don't point directly at my eyes), I.R. LEDs and lights with I.R. filters on.

. . . . and this whole thread has just started a big fight between me and my dad, who says that you just CAN'T see I.R.

 

[mgb_phys]

You can't see IR (pretty much by definition), what you can see is the 1 in a billion red photons that are 6 sigma away from the peak wavelength.

 

[Corkie2003]

Yeah, thanks, thanks a lot - sometimes it's more important to win an argument than tell the truth you know!

 

[unitone101]

Well, I tried this for a test. If I aim my remote towards my eye, and click the remote I can't see anything, and my pupils don't react. I tried it on a few of my family members and nothing happens. But if I aim it at my girlfriend, her pupils contract! So it's hard for her to lie or try watching my fingers or wathever. As far as I'm concerned, my girlfriend CAN see the infrared light on my remotes. Her pupils respond to them and I can't believe she can contract or dilate them at will. And anyways, she doesn't lie and doesn't care for seeing IR or not. She's actually just fed up of me pointing the remote at her eyes but I'm still fascinated by this.

God, I still remember seeing her using the remote as a flashlight.

 

[mgb_phys]

As far as I'm concerned, my girlfriend CAN see the infrared light on my remotes. Her pupils respond to them

If her pupils are V shaped and you seem to go through a lot of pet hamsters - you should be concerned!

 

[Redbelly98]

I used to work with lasers, and could see the IR from a 794 nm laser diode. 1/2 W, focused down to a 100 micron spot.

 

[DaveC426913]

You can't see IR (pretty much by definition)...

Why do you say this? The definition of IR isn't "below the visible light threshold of humans", it is simply "below red". And "red", as with "IR", is not well-defined in terms of frequencies.

 

[mgb_phys]

Why do you say this? The definition of IR isn't "below the visible light threshold of humans",

It's a pretty good definition!
CIE defines it as 700nm
Photographic astronomers define it as 730nm ( I band =806nm +- 75nm)
CCD astronomers define is as 1050nm cut-off of silicon
Modern astronomers define it as J band 1.2um same as comms fibre people - it's the first water band gap.

 

[DaveC426913]

It's a pretty good definition!
CIE defines it as 700nm
Photographic astronomers define it as 730nm ( I band =806nm +- 75nm)
CCD astronomers define is as 1050nm cut-off of silicon
Modern astronomers define it as J band 1.2um same as comms fibre people - it's the first water band gap.

That's fine. So then how can you state categorically that humans cannot see those wavelengths?

Or, at least, how can you correlate the threshold of IR with the limit of human colour perception?

 

[mgb_phys]

There is obviously some variation in the limit of human vision from person to person.
The limit is somewhere around 750nm it could easily vary by 10nm - but I don't think it extends to 880nm!
However cheap IR leds with a nominal peak at 880nm and a 30nm bandwidth can emit a small amount of light at several times this bandwidth. And remember that a dark adapted eye, especially peripheral vision, is amazingly sensitive - it can easily detect single photons.

 

[DaveC426913]

There is obviously some variation in the limit of human vision from person to person.
The limit is somewhere around 750nm it could easily vary by 10nm - but I don't think it extends to 880nm!
However cheap IR leds with a nominal peak at 880nm and a 30nm bandwidth can emit a small amount of light at several times this bandwidth. And remember that a dark adapted eye, especially peripheral vision, is amazingly sensitive - it can easily detect single photons.

But you're missing a critical factor: one person can see them, the rest cannot.

Assuming normal people can see "plain old red" it follows that the frequencies normal people cannot see must be infra-red. i.e. Whether or not the light from the LED is wide-spectrum, 99% of normal people cannot see it. That would make it IR.

Now we introduce a few rare people that still can see the light.


So, I guess I'm turning your definition on its head:

You said, "if people can see it, then, by definition it's not IR".
I'm saying, if (normal) people can't see it, then, by definition it is IR. This allows for the possibility that some can.

 

[mgb_phys]

But you're missing a critical factor: one person can see them, the rest cannot.

We don't exactly have a controlled experiment with the same LED being used by everyone. People's night vision definitely varies and it takes upto 20mins to become completely dark adapted.

I don't know what the ultimate cut off wavelength of rhodopsin is but it can't really vary from person to person - the molecule is the same. What varies is the number/density of rods, the ability of the brain to process low level signals, the amount of time they are prepared to stand around becoming dark adapted - and the stability of the IR led.

 

[DaveC426913]

We don't exactly have a controlled experiment with the same LED being used by everyone.

I did the experiment with a half dozen people and one remote. Only one person could see it. Not a big sample I'll grant but enough to demonstrate that it is not common and it definitely varies by the person, not by the electronics.

 

[mgb_phys]

The night vision acuity - their ability to see very faint red light - varies from person to person. None of them are able to see light much beyond 750nm.

 

[DaveC426913]

The night vision acuity - their ability to see very faint red light - varies from person to person. None of them are able to see light much beyond 750nm.

My experiment was in broad daylight with a thick blanket over their head. Zero time for acclimatization.

And as for "very faint", he was able to call it as fast as I could press the button. "OnOffOnOffOffOffOffOnOffOn..." and I couldn't fool him even by faking button-presses. I could press or unpress a zillion times and he'd get it right 100%.