pelican nemo 4C, purple beam?

[ehoffman]

hello,

does anyone have the Pelican Nemo 4C light? i bought one and decided to use it on a dive with low visability yesterday and to my surprise, the beam was purple and not much use at all. I checked the specks after the dive and low-and-behold, it has a xenon beam. is this supposed to be purple underwater cause on land it shines yellow, like a regular light? also, does the light come with some kind of filter that needs to be removed before use that i just didnt see in the instructions?

many thanks,
em

 

[Rev. Blade]

Is this supposed to be purple underwater cause on land it shines yellow, like a regular light?

I suspect you're seeing a "white balance" issue. Your brain knows what color some things are supposed to be (like a person's skin), so it adjusts what your eyes detect, to match what you brain thinks should be there. As you get deeper, the water filters out the light (starting by removing the red colors and if you got deep enough, it would remove the blues.) Your brain tried to add in the red it thinks it should see. When you turn on a light, it projects a beam (the color you see on land) that did not have to pass through a filter (all the water above you). Your brain is adding a bunch of red (because of the things you see that you are not lighting with your light), and your flashlight is putting out light that actually has some red.

If you were looking for a super nerdy explaination, you may find something at Wikipedia. ...but in general; the color you see on land is the "real" color of your light, and the color underwater is your brain fighting with a filter. The deeper you are, the redder your light.

 

[Halthron]

I have the 8-C version and it works fine.

The deeper you are, the redder your light.

Sorry, but that's incorrect. Water filters out certain wavelengths with distance travelled, not with depth. The distance from the diver's eye to the light beam will be fairly short, so short that reds may begin to be filtered out since they are the FIRST to be filtered.

Regardless, my 8-C Nemo has a yellow output.

 

[Rev. Blade]

...the water filters out the light (starting by removing the red colors and if you got deep enough, it would remove the blues.) .

...The deeper you are, the redder your (flash)light (will appear).

We agree that water filters red before blue. Perhaps I phrased my reply poorly. I should have emphasised some different words. Perhap the (edited) quote states it more clearly.