Exactly how much brighter is a green than a red?

AndyR · Mar 9, 2010

I've seen quite a few different answers, from 4 to 40 times brighter than a red laser. Not looking for a specific number, but something to give me a rough estimate on how bright my 200 mW dilda will appear... like a 5mw green? 20?

photonaholic · Mar 9, 2010

This explains it all.... figure red=10% apparent brightness to same power green.

chipdouglas · Mar 9, 2010

real world results are different though. I can see my 100mw(tested) blu ray much better than i can my 180mw(tested) red, which happens to be almost invisible until smoke is introduced.

michael

photonaholic · Mar 9, 2010

I read that it has something to do with luminescence of the air or something like that..

ninja_tux · Mar 9, 2010

chipdouglas said:
real world results are different though. I can see my 100mw(tested) blu ray much better than i can my 180mw(tested) red, which happens to be almost invisible until smoke is introduced.

michael

That's interesting...My guess is that it might vary based on the what the the violet light is interacting with before it reaches your eyes. Low wavelengths have a tendency to have more physical interactions with what they encounter (hence the incredible fluorescence power of violet light). EDIT: photonaholic beat me to this point. I need to learn to post faster and not ramble on so much

I also am pretty sure that different individuals have different sensitivities to certain parts of the visible spectrum, so you might actually be more sensitive to lower wavelengths (the violet part of the spectrum) than higher wavelengths (the red part).

photonaholic · Mar 9, 2010

you can't ever post as fast as me. :eg:

AndyR · Mar 9, 2010

Hm... so that's probably why I've been seeing such varied answers...
Thanks for the help

Grix · Mar 9, 2010

There is no absolute answer, because it's all up to the individual's eyes.

Also, the reason blu-ray is brighter than it should be is because of Rayleigh scattering. It's the same reason why the sky is blue.

Rayleigh scattering - Wikipedia, the free encyclopedia

photonaholic · Mar 9, 2010

Bob, I just got my first ever blu ray laser not too long ago, Not bad, but I'm not real impressed either.

outside at night, I can see a faint beam, the dot is hard to see at a distance unless it is striking the right surface.

Construction site orange road signs lite up really freaky at this wavelength.

Emc2 · Mar 9, 2010

AndyR said:
I've seen quite a few different answers, from 4 to 40 times brighter than a red laser. Not looking for a specific number, but something to give me a rough estimate on how bright my 200 mW dilda will appear... like a 5mw green? 20?

Hey Andy there is a guy named Marco Nero who lives in Austrailia and he has an impressive laser gallery. Here is a photo of him comparing two greens and a red, 10mW, 30mW, & 100mW

<10mW <30mW <100mW photo - Marco Nero photos at pbase.com

43mW (green) VS 100mW (red)

<43mWG Vs <100mWR photo - Marco Nero photos at pbase.com

Visually green is very btight when compared to red.

-Todd

chipdouglas · Mar 10, 2010

BobH said:
I'd question the meter you used. 180mW at 650nm should be blasting bright. According to that chart, 60mW at 633nm should be the same as 180mW at 650nm, and 60mW from a he-ne is a whopping strong beam.

My blu-ray and my red were tested on scopeguy's LPM.

key words high lighted.. "should be" peoples eyes percieve things differently or that statement would be "is" and in that case we could argue about what the the definition of "is" is LoL.

chipdouglas · Mar 10, 2010

i promise you bobh that in my eyes, with all the values i've stated above that i see my blu-ray dramatically brighter. tested in many conditions too. outside, foggy nites, crystaly clear nites, in my house with just standard dust inside with fog machine. in big bear mountain.... in every envronment i've used them the blu-ray is significantly brighter.

Greenmechanic · Mar 11, 2010

Blu-Ray does exhibit some interesting properties.
As has been stated, air, different eye sensitivity and other factors play into how "bright" it appears.

Do this simple experiment:
Pick a spot on one of your walls and shine the laser.
Turn the lights out and observe the brightness of the beam.
Now take several sheets of white paper and place them parallel to the beam, 3-4 feet away.
Now unless your laser has terrible divergence, the papers 3' away should not effect the brightness of the beam, right?
Observe the beam in the dark, now. (this effect might just be a contrast illusion, but it only happens with 405nm)

buster7467 · Mar 13, 2010

First off let me say that i am very color blind so even when i can see the beam of my 6x bluray i cant really tell you it is violet but i can see the beam very well. I hooked up a LCC red diode running at 350mA and the dot was really bright but i could not see the beam unless i used smoke. I dont know if it has anything to do with me being color blind or not but i can see the bluray beam extremely well even in a well lit room.

ossumguywill · Mar 13, 2010

^happens to me too. But it seems to work better inside, might just be light pollution. I can turn on both the ~100mW PHR and the ~250mW LCC in my labbie, and if used outside, the beam of the BR is much brighter, while the dot is a lot less bright than the red dot.

Exactly how much brighter is a green than a red?

AndyR

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