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06-03-2015, 05:13 AM #1
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808nm appears red to me like 650nm, why?

When I see the dim spot from a 808nm laser pointer the shade of red looks much the same to me as a 650nm laser, why is that? I know the wavelength is hugely different yet I don't see much difference. I speculate it's because the red color receptors in our eyes can pick up a little of the energy but can't produce anything redder than 650nm, thus we perceive the only red we can perceive... What do you think?

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http://www.lexellaser.com/techinfo_wavelengths.htm

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Angular Size Calculator; use with diode angle of radiation specification to calculate the needed lens diameter for a given FL:
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Divergence to spot size calculator: http://tinyurl.com/spotsize - 1 mRad is about .057 degrees which from the earth would expand to be ~10% the diameters of the moon or sun at their distances.

Divergence Calculator: http://www.pseudonomen.com/lasers/ca...alculator.html - Measure your lasers beamwidth at 1 foot & then at a further distance to calculate the divergence.

Online calculator to determine spot intensity at different mRad's & powers @ distances: http://tinyurl.com/divergence-calculator

Laser Power Density Calculator: http://www.ophiropt.com/laser-measur...ity-calculator

How to build a laser beam expander to reduce divergence: http://tinyurl.com/BeamExpander

RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness

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Last edited by Alaskan; 06-03-2015 at 05:21 AM.

06-03-2015, 06:11 AM #2
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doubleone44
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Well, you have three types of cones in your eyes. Green ones for green light, blue ones for blue light, and red ones for red light. The sensitivity for say, red light is different for each wavelength, and for some people, it can just stop around 650nm because red is then fully saturated, but the other types of cones are not even used. This is different for everyone of us and so for some people 660nm looks exactly like 685nm, while for others they are a world of difference.

06-03-2015, 07:17 AM #3
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Sigurthr
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Re: 808nm appears red to me like 650nm, why?

When only the red cone is stimulated you'll see what your brain perceives pure red as. If 650nm only stimulates your red cone, then 650nm and up will all look the same barring nonlinear processes, oddball stimulations, or fluorescences.

At 660nm red looks pure to me. At 720nm it looks a bit maroon. At 780nm it looks redder. At 808nm it's very cherry red. At 848nm it looks like 660nm.

Everyone perceives wavelengths a bit differently, and everyone has different ranges they can see.
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06-03-2015, 12:40 PM #4
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lazeristasUVISIR
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Re: 808nm appears red to me like 650nm, why?

Quote:
 Originally Posted by Sigurthr At 848nm it looks like 660nm.
That's far. What was a laser power of 848?
I could not see anything >810 nm.
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06-03-2015, 12:50 PM #5
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Re: 808nm appears red to me like 650nm, why?

"thus we perceive the only red we can perceive... What do you think? "

Yeah, well, you can't beat that logic..........

06-03-2015, 08:05 PM #6
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Re: 808nm appears red to me like 650nm, why?

Quote:
 Originally Posted by lazeristasUVISIR That's far. What was a laser power of 848? I could not see anything >810 nm.
It was <0.1mW. Spectral sensitivity varies greatly between individuals.
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06-04-2015, 02:20 AM #7
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Constandinos97
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Re: 808nm appears red to me like 650nm, why?

I stripped apart my 532nm laser (cheap Chinese one, don't worry) and made it an IR burning laser. Honestly, i did not expect 808nm to look that red. It was fairly dimmer than my 650nm pointer, but the dot (actually it was bar-shaped, so not really a dot) was visible across the room (barely, but I could still notice it). I'm not sure if it looked exactly like 650nm, but it's very close to it
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06-04-2015, 02:36 AM #8
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Re: 808nm appears red to me like 650nm, why?

My converted 532nm to a IR burner does the same thing, makes a cherry red rectangle or bar across the room at about 225mw, after collumation. If I focus it tightly, it is a tiny red point, but when I shoot it through an expander, I can see it really is that bar shape.
__________________

http://www.lexellaser.com/techinfo_wavelengths.htm

Laser Safety:
http://www.laserpointersafety.com/index.html

Angular Size Calculator; use with diode angle of radiation specification to calculate the needed lens diameter for a given FL:
http://www.1728.org/angsize.htm

Divergence to spot size calculator: http://tinyurl.com/spotsize - 1 mRad is about .057 degrees which from the earth would expand to be ~10% the diameters of the moon or sun at their distances.

Divergence Calculator: http://www.pseudonomen.com/lasers/ca...alculator.html - Measure your lasers beamwidth at 1 foot & then at a further distance to calculate the divergence.

Online calculator to determine spot intensity at different mRad's & powers @ distances: http://tinyurl.com/divergence-calculator

Laser Power Density Calculator: http://www.ophiropt.com/laser-measur...ity-calculator

How to build a laser beam expander to reduce divergence: http://tinyurl.com/BeamExpander

RHD's Relative Perceived Brightness Calculator. Compare brightness @nm: http://lsrtools.1apps.com/relativebrightness

YAG Power Calculator, i.e. convert ns @ mJ to peak power in watts http://tinyurl.com/YAG-Pulse

The forum costs more to run than donations received, if you wish to help click this link: http://laserpointerforums.com/donations.htm

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06-04-2015, 03:55 AM #9
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Re: 808nm appears red to me like 650nm, why?

My 808nm lasers dot looks dark red/maroon to me.

06-04-2015, 12:08 PM #10
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Re: 808nm appears red to me like 650nm, why?

There was a post a long time ago, by zyxwv99 if I'm not mistaken, where he included a link to a scientific paper explaining the reason. From what I remember it's pretty much what Sig said, at around 650nm it stimulates just the red cones, after that it starts to stimulate a bit of blue (hence the maroon), which goes up to 700nm and then drops back, which makes further IR look like more like "regular" red.

lazeristasUVISIR, I can see a dot of 850nm at around 8mW just fine.
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638nm: Classic from Lazerer (409.3mW pk|389.4mW avg|415mW rtd)
650nm: NewWish (10.6mW pk|5mW rtd) | Dilda (216.3mW avg|200mW rtd)
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780nm: module (2.7mW avg|5mW rtd)
808nm: Classic modded from a 532nm (162mW avg)
850nm: module (8.8mW avg|7mW rtd)
980nm: NewWish (81mW pk|5mW rtd) | 2nd line around 490nm

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06-04-2015, 01:10 PM #11
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lazeristasUVISIR
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Re: 808nm appears red to me like 650nm, why?

Quote:
 Originally Posted by Atomicrox lazeristasUVISIR, I can see a dot of 850nm at around 8mW just fine.
I wish too, through my hands pass a lot of them, and it would make my life easier
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06-04-2015, 11:17 PM #12
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Sigurthr
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Re: 808nm appears red to me like 650nm, why?

Quote:
 Originally Posted by Atomicrox There was a post a long time ago, by zyxwv99 if I'm not mistaken, where he included a link to a scientific paper explaining the reason. From what I remember it's pretty much what Sig said, at around 650nm it stimulates just the red cones, after that it starts to stimulate a bit of blue (hence the maroon), which goes up to 700nm and then drops back, which makes further IR look like more like "regular" red. lazeristasUVISIR, I can see a dot of 850nm at around 8mW just fine.
Edit:
Found that post: What is the longest wavelength of laser light you have seen?

Do you remember the post about a russian? study that showed the extreme limits of human vision, even at unsafe levels? I'm looking for that next.
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Last edited by Sigurthr; 06-04-2015 at 11:27 PM.

06-04-2015, 11:42 PM #13
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Re: 808nm appears red to me like 650nm, why?

I do remember, but I couldn't find the exact post. There's related stuff on these:
Real UV flashlight

Slightly crazy 980 nm laser experiment

405nm vs scotopic vision?

I'm still interested on this subject, just unable to order further stuff to test :/
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high 450nm: NewWish (12.6mW pk|5mW rtd) | Dominator by Blord (3010mW pk|2779mW avg during 5min)
462nm: 501B by Atomic (1507mW avg)
473nm: BWB-10-OEM labby by CNI (10mW rtd)
520nm: MXDL pen by DTR (31.6mW pk|28.8mW avg)
532nm: NewWish (28.6mW pk|26.8mW avg|10mW rtd) | Dapper (30.3mW pk) | Classic (120.0mW pk|103.1mW avg|100mW rtd) | "The Green Box" by Atomic (176.7mW pk|140.0mW avg)
589nm: Spartan from Dragon Lasers (58.4mW pk|37mW avg|50mW rtd)
632.8nm: HeNe pointer by Atomic (0.68mW rtd)
635nm: NewWish (4.6mW avg|5mW rtd)
638nm: Classic from Lazerer (409.3mW pk|389.4mW avg|415mW rtd)
650nm: NewWish (10.6mW pk|5mW rtd) | Dilda (216.3mW avg|200mW rtd)
685nm: laser-in-a-box by Atomic (30.4mW pk|29.3mW avg) | 501B by Atomic (32.4mW avg)
780nm: module (2.7mW avg|5mW rtd)
808nm: Classic modded from a 532nm (162mW avg)
850nm: module (8.8mW avg|7mW rtd)
980nm: NewWish (81mW pk|5mW rtd) | 2nd line around 490nm

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06-05-2015, 12:32 AM #14
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Sigurthr
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Re: 808nm appears red to me like 650nm, why?

A bit of research turns up a Color Plot for sub-400nm wavelengths. It isn't far into UV, but hey, it's something.

http://starklab.slu.edu/UVColorCircle.jpg

Now, if we could fine one for IR...
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06-05-2015, 01:19 AM #15
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Re: 808nm appears red to me like 650nm, why?

Quote:
 Originally Posted by Sigurthr Edit: Found that post: What is the longest wavelength of laser light you have seen? Do you remember the post about a russian? study that showed the extreme limits of human vision, even at unsafe levels? I'm looking for that next.
Maybe in this thread: What is the wavelength of pure yellow?

Alan
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06-05-2015, 02:05 AM #16
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Atomicrox
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Re: 808nm appears red to me like 650nm, why?

Pretty interesting, what's the number close to the 425? 400, perhaps?

A few months ago after hearing my ex-boss tell me he had cataract surgery I took a 365nm flashlight to work and tested him. He claimed to see a very strong lilac light with the eye that had the surgery, while the other eye could only see the usual "visible leak" from those flashlights. I believe he was telling the truth, he tried first with prescription glasses on and couldn't see the UV. When he removed the glasses he seemed genuinely startled to see the light.
I tried to get him to describe the color but he's not good at that
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405nm: NewWish (29.1mW avg|5mW rtd) | Dilda (81.5mW avg|200mW rtd) | 501B by Blord (633mW pk)
low 445nm: C6 from Survival Lasers (1351mW pk|1289mW avg|1100mW rtd)
high 450nm: NewWish (12.6mW pk|5mW rtd) | Dominator by Blord (3010mW pk|2779mW avg during 5min)
462nm: 501B by Atomic (1507mW avg)
473nm: BWB-10-OEM labby by CNI (10mW rtd)
520nm: MXDL pen by DTR (31.6mW pk|28.8mW avg)
532nm: NewWish (28.6mW pk|26.8mW avg|10mW rtd) | Dapper (30.3mW pk) | Classic (120.0mW pk|103.1mW avg|100mW rtd) | "The Green Box" by Atomic (176.7mW pk|140.0mW avg)
589nm: Spartan from Dragon Lasers (58.4mW pk|37mW avg|50mW rtd)
632.8nm: HeNe pointer by Atomic (0.68mW rtd)
635nm: NewWish (4.6mW avg|5mW rtd)
638nm: Classic from Lazerer (409.3mW pk|389.4mW avg|415mW rtd)
650nm: NewWish (10.6mW pk|5mW rtd) | Dilda (216.3mW avg|200mW rtd)
685nm: laser-in-a-box by Atomic (30.4mW pk|29.3mW avg) | 501B by Atomic (32.4mW avg)
780nm: module (2.7mW avg|5mW rtd)
808nm: Classic modded from a 532nm (162mW avg)
850nm: module (8.8mW avg|7mW rtd)
980nm: NewWish (81mW pk|5mW rtd) | 2nd line around 490nm

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Last edited by Atomicrox; 06-05-2015 at 02:06 AM.

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