RED Laser VS Green Laser ?

[johndiver999]

Red light apparently only penetrates about 20 feet of water, so I think a red laser would not extend much past that range. Green is much less attenuated. And I know they can shine past 25 feet in clear water

 

[D_Fresh]

As long as you don't shine it in their eyes, I have no problem. A lot of the smaller territorial fish genuinely start to act like cats around the dot. Clowns, damselfish and sergeant-majors in particular have a great time chasing it around.

Hahahaha, True true. Something nefarious, along the lines of leading a clownfish right to a predator, would be bad. But leading a clownfish around its anemone like a cat could be hilarious!

Johndiver, I know water is rather inefficient at transmitting light, especially with suspended solids (silt, plankton, bio matter, etc), but only 20 to 25 feet? I have no experience with a laser underwater, you may well be correct, I'm just kind of surprised it's that short. I think this call for some very unscientific testing!

 

[lucca brassi]

@EireDiver606

IMO a red laser would be more useful as it’s easier to see in a “green” environment. Green laser would be harder to see in greener environments.

?

ever heard green environment absorb all colors except green & red environment absorb all colors except red ??

 

[Johnoly]

..., you can shine the laser straight up and the searchers will see the beam and be able to track to surface location.

WOW,,that's a great tip!!
I carry a green laser in my U/W VHF radio canister. It makes great sense to point the laser at the Aircraft/Ship/Boat to 1st get it's attention. But then the pilot is going to say "Where the Heck did that come from? ". By then pointing the laser straight up and maybe make some small circles, you are creating an "Arrow cone" pointing directly downward at the diver and his location. GREAT RESCUE TIP !!

 

[D_Fresh]

@EireDiver606

IMO a red laser would be more useful as it’s easier to see in a “green” environment. Green laser would be harder to see in greener environments.




ever heard green environment absorb all colors except green & red environment absorb all colors except red ??

lucca, I think you may be a little confused there, mixing two different scenarios; underwater environment and Color Theory.

Regarding the former, within a reasonable distance red would stand out as it is contrasting to the surrounding environment. But due to the color absorption of water, a red light would absorbed within a shorter distance than blue or green, assuming "clear" seawater:

Red (665 nm) penetrates approx 15 meters (49 ft)
Orange (630 nm) penetrates approx 30 meters (98 ft)
Yellow (600 nm) penetrates approx 50 meters (164ft)
While Violet (400 nm), Blue (470 nm), and Green (550 nm) penetrate as deep as 200 meters (660 ft).

(The above info is readily available from PADI, NOAA, and others, and is regarding depth penetration, not horizontal distances at any given depth.)

Regarding Color Theory, if only blue light were cast upon a red shirt, the shirt would appear nearly Black, because there is little to no red light to reflect. A green colored couch lit by red light also appears Black, because there is no green wavelength of light to reflect back. This is because the pigments absorb all other wave lengths of light Except for a specific wavelength. Blue shorts look blue in white light (which is a combination of all wavelengths) because it absorbs all except the 470 nanometer wavelength, reflecting Blue. Same with, say, a red shirt; absorbing all except 665 nanometer wavelength thus appearing Red

I am a theatrical lighting designer

 

[Aviyes]

WOW,,that's a great tip!!
I carry a green laser in my U/W VHF radio canister. It makes great sense to point the laser at the Aircraft/Ship/Boat to 1st get it's attention. But then the pilot is going to say "Where the Heck did that come from? ". By then pointing the laser straight up and maybe make some small circles, you are creating an "Arrow cone" pointing directly downward at the diver and his location. GREAT RESCUE TIP !!

Be careful about shining it at the rescue aircraft. You don't want to potentially blind the pilots searching for you. Though this all depends on the laser characteristics. I do like the straight up cone idea.

 

[RainPilot]

You are much better off not trying to shine directly at the rescue craft, it’s way easier to see a beam from the side than a dot from the front, as well as the obvious issues with shining a laser into eyes/intensifiers.

We would shine straight up and even small hand movements become exaggerated at distance so it made a cone of sorts.

 

[EireDiver606]

@EireDiver606

IMO a red laser would be more useful as it’s easier to see in a “green” environment. Green laser would be harder to see in greener environments.




ever heard green environment absorb all colors except green & red environment absorb all colors except red ??

Yes thanks for pointing that out. I completely forgot that!
Edit: after reading @D_Fresh post....

 

[lucca brassi]

blue l. / blue e.

green l. / blue e.

green l. / green e.

red l.......?

 

[D_Fresh]

Hahaha cool triggerfish. Nice videos lucca.

I still maintain that it's a product of contrast though. And in the last video the general visibility is causing backscatter, so any color would be more visible there.

But that's also why I think it's a great excuse for some fun time testing