visible laser distance 532-650-405nm

[zxn474l]

I know that 532nm green is the brightest, then 650, then 405nm but, I have heard visually that red seems to GO FARTHER in the sky than green and 405 GOES FARTHER than red is that true as far as what the human eye can focus on? ALSO on a "foggy" night will a 405nm be really visible...I do not own one yet.

 

[HumanSymphony]

I know that 532nm green is the brightest, then 650, then 405nm but, I have heard visually that red seems to GO FARTHER in the sky than green and 405 GOES FARTHER than red is that true as far as what the human eye can focus on? ALSO on a "foggy" night will a 405nm be really visible...I do not own one yet.

I think you've got it all wrong. It would be green that looks to go the farthest since it is the most visible. Next in line being red, and violet last. Heck, I can barely see the dot of 100mW of 405nm at like 100 feet.

Fog works wonders for ALL of these colors

 

[davidgdg]

I know that 532nm green is the brightest, then 650, then 405nm but, I have heard visually that red seems to GO FARTHER in the sky than green and 405 GOES FARTHER than red is that true as far as what the human eye can focus on? ALSO on a "foggy" night will a 405nm be really visible...I do not own one yet.

Red beams seem thinner and sharper to me, but they may be just because they are not as dazzling. I actually prefer them sometimes since they attract less attention from neighbours.

405 is a strange one. It is not particularly visible because our eyes are operating right at the limit. Also, most people have difficulty focusing on the spot - so you get weird halo effects. They are certainly not good long-distance lasers. I have a 130mw 405 and the spot is barely visible more than about 200 yards away. Compare big greens and reds for which the spot can easily be seen from half a mile or more. On the other hand, 405s are great for fluorescence and colour mixing. Try 405 on green and you get a lovely soft blue (best viewed if you are short sighted - makes the spots look bigger)

As for fog - fantastic - makes the beam of even low powered lasers look solid. Even 405 looks brilliant (literally) in fog. Clear conditions are best for seeing the spot at a distance, but for general fun and interesting effects, fog beats everything. Shame we only get it a few nights a year. As a surrogate, try a freshly boiled kettle. Open the lid and shine the laser through the steam. Fun fun fun !

Enjoy

David

 

[Ivan]

I thought red went the farthest :thinking:. I get fog a lot in my area so im set for some awesome beams.

 

[RA_pierce]

How "far a laser goes" is dependent a few things...

First, Divergence.
Generally, reds have better divergence than greens because of the optics used. This does not meant green lasers have inherently poor divergence. With the right setup, the same or better divergence can be achieved.
Better divergence means that the beam will be visible over a longer distance.

Second, the human eye's response to different wavelengths.
Green is brightest. Red and Violet are close to the same "brightness" mW for mW.
Green and red are "easy" for our eyes to focus on. Near UV is difficult. Violet lasers will appear blurry or fuzzy even though the divergence is about the same as what you get with typical red lasers.
This poor perception of Violet makes it look like the beam doesn't travel as far.

Third, atmospheric conditions and rayleigh scattering.
Short wavelengths (blues and violets) are scattered by the atmosphere (moisture, dust, and air) more than longer wavelengths like green and red.
This means that the beam of a violet laser will be attenuated by the air much more quickly than the beam of a red laser. On the other hand, this makes the beam appear brighter since more light is being reflected towards you.

If you have a red, green, and violet laser with equal divergence, power, and beam diameter... and point all 3 into the sky on a clear, dark night with average humidity, the green will be brightest and seem to travel the farthest, next will be the red, and the violet will look fuzzy after a couple meters.

 

[LaserRX]

An interesting thing to try is to use more then one laser of the same wavelength but different output powers and see where the beams stops. No matter what the output level of the laser they will all seem to abruptly stop at the same distance (few hundred feet) without any gradation.

While in actuality the beam does travel farther then this point, it will not appear so to those standing at or near the point of origin.