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Green 50mw vs blue/violet100mw

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th3pyr0

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I do not own a blue or violet laser. One thing I do know is that the human eye is not as receptive to that color as green is. pardon me if there is a similar thread about this as I couldn't find anything.

What would be the comparison between a 50mw green laser( I own the FLX model from Rayfoss) and a 100mw violet/blue( no specific laser, just in general) laser as far as how bright it is. Will a 100mw violet be brighter? dimmer? the same as a 50mw green? How do these 2 colors compare? Thanks!
 





J

joeyss

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It'll be noticeably dimmer. I have a 50 of both. You should still be able to see the beam at night , but the dot won't go that far. I'd say it's about 1/10th as bright as the 50mw green. It depends on what it hits as some things will fluorescence.
 
InfinitusEquitas

InfinitusEquitas

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joeyss said:
It'll be noticeably dimmer. I have a 50 of both. You should still be able to see the beam at night , but the dot won't go that far. I'd say it's about 1/10th as bright as the 50mw green. It depends on what it hits as some things will fluorescence.
Click to expand...

IMO not even 1/10th as bright. To me 150mW of 405nm (violet) appears about as bright as 10mW of green.

There is some variation in how individuals perceive the lower wavelength.
 
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joeyss

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Actually if you're in a room and you shine at something it will be 1/10 to 1/5 due to the subtle florescent effects espically if you have a bed and the white sheets are uncovered , but yea it loses once you hit something like a tree 30 feet away outside. Heck my camera shows the 50 mw 405 while it dosen't even pick up a 30 mw or so 532 lighting up my room. Strange isn't it? I think I may be able to see it better than most people since I can see the beam when it's not even fully dark or in situations where I can't see my red 50 mw beam. Also my 50mw red looks dimmer in terms of how it lights up my room even though the dot looks much brighter outside at night. It gets a bit freaky at sometimes.
 
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Fenzir

Fenzir

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I personally have a 100mw 405nm laser and a 50mw and I can NOT see the beam at all. These lasers are LPM'd and still burn really nice. Most, if not all of my friends say they can see the beam, but I can hardly see the dot. It really is different from person to person and I have 20/20 vision. Even when I smoke a room up, I can just hardly see the beam while I can easily see the beam on a 1mw red laser, however, I blame my eyes.
 
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joeyss

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Strange isn't it? If you add just a slight bit of fog I see the full beam of my 50 mw red. When my o-like 200 mw red worked I was able to see the beam a little bit better than my 50 mw 405. It also looked more "normal" and not like some strange alien light.
 
InfinitusEquitas

InfinitusEquitas

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With smoke I can see either clearly... without it, to visibility of 150mW of 405nm is about the same as 200mW of red.

What does bug me a great deal with 405's is that I can't see a dot... I see a kind of hazy bright blob. Same effect with 445's but not nearly as pronounced.

Lastly... I can't stand to see the dot of a 445 indoors. Even from a perfectly safe distance, ~100mW of 445nm dot from 5 feet away on an off white wall, leaves kind of yellow after images, and generally strains my eyes.
 
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joeyss

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Lasers never strain my eyes unless they're too bright and up close(that's why you use googles) , but you can see your eyes trying to focus it if you're in a dark room and hold your head steady and try not to move your eyes for a second or two before and after comes on. If you move your eyes you see it shrink and then get bigger like it's going back in focus.
 
Fenzir

Fenzir

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Funny, I can see the beam of my 5mw red laser, although I could never figure out if it was 635nm or 650+.
 
Vextor

Vextor

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@rhd: Does that calculator consider the beam thickness? I mean, the beam from a green is usually much more concentrated than other colors. So, I think the Rayleigh scattering is proportional (?) to the density of the beam.
 
rhd

rhd

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Vextor said:
@rhd: Does that calculator consider the beam thickness? I mean, the beam from a green is usually much more concentrated than other colors. So, I think the Rayleigh scattering is proportional (?) to the density of the beam.
Click to expand...

Interesting thought -

At the same time, a more densely concentrated beam should engage Rayleigh scattering to a greater degree per mm of thickness. So I think it balances the equation.

That said, for non-Rayleigh reasons, beam thickness probably DOES need to be taken into account at some level. I can illustrate why by suggesting the border-case of taking a three-foot-wide beam. Even a 100mW of 532 would probably have almost no visible brightness at 3 feet wide, while a 2mm beam of the same power would be highly visible.

This border case would never arise in practice, but it at least illustrates that thickness of the beam should have some impact on perceived brightness.
 
Vextor

Vextor

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I agree.

Another doubt I have on that calculator is: Does it consider the light-adapted (photopic) or the dark-adapted (scotopic) human sensitivity? It should be the scotopic since we enjoy our beams at dark. At least it should be somewhere between both sensitivities, considering lit rooms.
 
rhd

rhd

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Vextor said:
I agree.

Another doubt I have on that calculator is: Does it consider the light-adapted (photopic) or the dark-adapted (scotopic) human sensitivity? It should be the scotopic since we enjoy our beams at dark. At least it should be somewhere between both sensitivities, considering lit rooms.
Click to expand...

This part has been discussed at length actually. Beams will always be sensed by the light-adapted vision, because they are an intensely bright light source.
 
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