limp-wristed sissy boy --my petzl headlamp has 4 brightness settings. How many does your fairy crown have?
Homo erectus, Mine has 3, plus a real sweet blinking setting for doing disco dancing around a campfire for you in my cute biker shorts.
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limp-wristed sissy boy --my petzl headlamp has 4 brightness settings. How many does your fairy crown have?
Okay, I'll resotre an old thread instead of starting a new.
Do the green lights (or red I guess on some) really do what they say? Preserve your night vision and animals don't see it?
I bought a little Petzel Tika, has 3-4 LED's and runs on 3 AAA. So far its the best $30 I've spent.
As I understand it, the Red/Green light issue is partially myth, partially true.
To paraphrase from various sources:
Your eyes see with rods. The rods detect light volume (black/white-basically your human night vision). The rods detect light by the destruction of a photopsin chemical called rhodopsin. Flash a bright light in your eyes and the spots you see are bits where the rhodopsin is now gone. Stay in the dark for a while and you build up a surplus of rhodopsin and your eyes are ultra-sensitive to light (night vision). Since the rods only see black and white, this is why things at night time look more like black and white rather than full color.
The rhodopsin "bleaches" or breaks down when struck with light - it's this breakdown that is detected by the nerves and that makes you "see" the light. The more rhodopsin that builds up in the rods, the better you can see really dim lights. It takes up to an hour to build up a full compliment of rhodopsin. Even starlight causes the bleaching (when you look at the stars, you detect it, hence the breakdown is occuring), but the rhodopsin builds back up easily since there was so little breakdown from such a dim light source.
A bright light in the detection frequency of rhodopsin instantly breaks down the rhodopsin that has built up - it's really sensitive stuff. Rhodopsin's detection frequency goes down to about 610nm (a nanometer is 1/1,000,000,000 of a meter). Dark red (and red LEDs) is below this frequency, so your Rods can't "see" red light. They are blind to it. You can blast your eyes with a really bright red light and still have your night vision for gazing at the stars with the Rods when the red light is turned off.
Green, however, is definitely in the detection frequency of the Rhodopsin and will bleach it right out. Green light = at least partial if not total loss of your natural "night vision" or "night adaptation" depending on the intensity. You then get to wait for up to an hour for the rhodopsin to build up again.
People think green is good for night vision due to their experiences with night vision equipment. This has resulted in the modern myth that green light preserves your natural night vision. This is not true and has resulted in a great deal of non-research based marketing by people trying to sell green LED lights.
People have known for a very long time that red light preserves night vision and want a "new and modern" way to preserve night vision, thinking that red light is the "old fashioned" way. However, our eyes havn't magically evolved over the last 50-100 years to suddenly accept green as a night vision preserving color. Dark red light is your only choice for preserving 100% of your natural rod-based night vision due to the anatomy of the eye and can be used at intensity levels that allow normal navigation and operation without night vision loss.
You CAN use a really super dim light of any color - about the brightness of starlight, which will break down rhodopsin slowly enough that it can make up for the breakdown on the fly. However all the LED products I've seen are way, Way, WAY too bright for this. Plus the whole idea of using red light is so that it can be bright enough for you to operate pretty much normally without losing your night adaptation. Using a super dim light won't allow anything close to "normal" operation.
AS to animals.. The wavelengths of light which an animal can percieve is going to vary largely from species to species. It would appear that some CAN see red light, and that some cannot.
One issue NOT addressed: Sportsmen specifically, have come to use green/blue lights because you can't see blood under a red light. However as I understand it, the green gives no advantage in preserving YOUR night vision over using a white light at dimmer levels, nor any advantage in blood tracking. However, IIRC your eyes cannot process blue and red at the same time. Since blood will not reflect any blue light, using a blue lense in theory would make the blood stand out. Still it would only appear dark and shiny, and wouldn't look any different than say a used motor oil trail. White light, still your best bet for blood trail work.
could you explain in a little more detail please....