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FrozenGate by Avery

Not feeling the love on 405nm visibility

HaloBlu said:
Different individuals visual limits at either UV / IR end is quite interesting. :pop:

Sigurthr: Is 1mW 848nm barely visible at least? Would that be the dot at 1mW? What color is it?
Have you tried a 337.1 TEA nitrogen laser? :D

mfo: At what power is that 980 visible to you & what color?
I read some see it as grayish or greenish instead or deep red.
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1mW of 848nm is -barely- visible, but it is also uncollimated. I figure that (by using 808 and 780 as an analog) if it were collimated I would be able to see it better as a spot. It looks deep red or reddish brown to me.

No, I haven't built a N2 laser yet, I'd love to though. I can very easily see the Mercury emission line at 365nm though, it is nearly as bright to me as the 406nm line.
 





405nm beams look "gray" to me regardless of power, I can barely see any color in them. The spot is definitely violet though.
 
scopeguy20 said:
For a bright beam of 405 you need fog... it is natural for 405nm to be about 1% the brightness of the same mW of 532nm light! -GH
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Indeed, the sensitivity for 405 nm is very low for people with normal vision... and some laser diodes have a slightly shorter wavelength making them even more invisible. On the edge of the spectrum, a few nanometers can make a big difference. If you had a 402 and 408 of equal power side by side, the latter would look much brighter.

As for relative brightness: The response isnt linear, 20 mW will not appear 'half as bright' as 10 mW under many conditions. Especially if the laser light is brighter than the environment (i.e. playing with it in a dimly lit room) you may not even notice a twofold difference in power unless you have the lasers side by side.
 
My eyes are fairly sensitive to 405nm I guess. Back when PS3 diodes were all the rage I had one at 15mW that had a visible beam. The color of the beam appears about the same as the tube lights up on a fluorescent blacklight.
 
Thanks Lase. I was just joking. :yh: I did buy the 405nm for something powerful yet more discrete than a 445nm.

My eyes are pretty bad when it comes to differentiating shades of green, not to mention doing abysmally at tests like this:

Take the Ishihara Color Vision Test
 
zxcctu said:
Thanks Lase. I was just joking. :yh: I did buy the 405nm for something powerful yet more discrete than a 445nm.

My eyes are pretty bad when it comes to differentiating shades of green, not to mention doing abysmally at tests like this:

Take the Ishihara Color Vision Test
Click to expand...

I'm good at them.... so good I had to ask my doctor which number he wanted me to read out cause I could see both :na:

Lase
 
Shorter wavelengths can appear brighter to younger people, so it may have to do with your age. Some of the CIE color matching corrections attempt to address this.

Also make sure your house is dusty. In the summer, when I have fans blowing in cool air at night, it is very easy to see the beam.
 
I agree. It's a harsh color. The reality is it's a blacklight laser. The violet color is on the periphery of what the eye is sensitive to.

The violet color, especially at high powers, aggravates my old eyes. However I've got a couple 405nm (DIYs) for the sake of the collection. And they do burn.
 
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I actually feel quite different about 405nm now that I have a high power (Class IV) one. It's quite bright to me and I was shocked how visible the beam is in non-fogged air. Rayleigh scattering at it's finest. If anything I'm less fond of my 1.3Watt 445 now, damn thing is too powerful to really enjoy. Inevitably I'm going to build a <1W 445 and sell the 1.3'er. I'm really enjoying my >680mW 405 now as well. Up next is a >100mW 405 and then maybe I'll make a second >650mW'er.
 
I don't like the color or the visibility of 405 lasers. I just purchased a 530 mw 405 and although i am dissapointed with the brightness, I am very pleased with how well it burns at very large distances.

High power and low visibility can be very usefull at times when you want to have some fun, but don't want to attract all the attention you deserve!
 
Sigurthr said:
I actually feel quite different about 405nm now that I have a high power (Class IV) one. It's quite bright to me and I was shocked how visible the beam is in non-fogged air. Rayleigh scattering at it's finest. If anything I'm less fond of my 1.3Watt 445 now, damn thing is too powerful to really enjoy. Inevitably I'm going to build a <1W 445 and sell the 1.3'er. I'm really enjoying my >680mW 405 now as well. Up next is a >100mW 405 and then maybe I'll make a second >650mW'er.
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The coolest thing is it's much better then a green laser of that power on a camera. My 500mw has a much brighter beam than any green laser when i film it due to scattering. It's also a fun to use as a perfectly coherent black light. Anyone else notice it seems to have more of a psychological effect in terms of somehow looking more profound VS other wavelengths?
 
The only effect i noticed with 405 nm is my eyes dont really focus on the dot, so it mostly stays a bit vague. I assume this has do do with different diffraction in the eye due to the short wavelength, cause the 405 to be out of focus a bit when your eyes focus on the wall that gets hit by the dot.

Not much of a benefit though ;)
 
Aye, my eyes can't focus 405nm well at all, but they're very good at detecting it!

I actually went out tonight and did a bit of starpointing. I've been eagerly awaiting the warm weather since september of last year, so I could go outside and enjoy my lasers. To my surprise, I was able to starpoint with as little as 25mW of 405nm, and easily follow the beam all the way up. It is a perfectly clear night, no fog or dust or mist in the air. Past about 50ft the beam blurs to be that of a shaft of light instead of a beam, but I could still follow it, it did look grey and not violet though.

My 2.5mW 532nm also did rather well, though the terrible divergence of a WL pointer didn't help much. I also tried my 120mW 405, 70mW 450, 1310mW 445, and my 200mW 658. The divergence on my 450 is worse than I thought it would be for a single mode diode, but not terrible. At about 35meters out the spot was about 1.75" in diameter. despite being nearly 2.5x as strong (70mW) and higher wavelength it wasn't really any more visible than my 25mW 405. My 120mW 405 did very well though it still had the blurry effect from the wavelength, but due to the nice divergence it still performed well. My 1310mW 445 did as expected, with it relying on brute force and not beamspecs. Definitely the brightest, but the beam was that of a big ole blob once it got up towards the stars. It wouldn't be good for pointing out a single star in a cluster.

The big surprise was my 200mW 658nm unit... focused to infinity the divergence was fantastic! I could also see the beam quite clearly with dark adapted eyes. It definitely had the most definition and clarity of all the lasers I tried and my eyes focused it effortlessly. I didn't measure the divergence because I don't know the exact distance of the target, but I walked up the target which was maybe 35meters out and the spot was only 16mm in diameter. Being waterproof and having a run time of nearly 8 hours and unlimited duty cycle this is the clear winner for starpointing. You could easily point out a single star in a cluster, and the spot could be seen on a treeline a little over a mile away with ease. All the other lasers I tried you could follow the beam but not see the spot, and the beam was very wide at any considerable distance. I expected my single mode blue to work a lot better than it did but it was no competition to the red.
 
I have a 45mW 405nm, my favorite, most unique thing about this wavelength, is how different the dot looks on different colors. It seems to change from violet, to gray, to light blue. It's crazy! And just cool, SCIENCE!!!
 
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