ebow86
Flashlight Enthusiast
A red light to perserve night vision isn't much good to me becuase I'm bound to blast off the high beam anyway, thus destroying my night vision, but I can see where alot of people find it useful.
Red light is preferable over white (or other colors), but the explanation given is wrong. I give references; you can google them, but I don't know if you can get the original articles. I can, being on a university network. Libraries should be able to get them, though.
The standard explanation already given is wrong, since both cones and rods react the same above wavelengths of 650 nm or so (red), but rods are much more sensitive at lower wavelengths, thus their night vision gets killed [S. Hecht and Y. Hsia, J. opt. Soc. Am. 35 (1945)]. Thus, for the same 'brightness experience' (for lack of a better understandable term) of red and white light, the eyes will recover more quickly if red light is used [E. O. Hulburt, 'Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors', J. opt. Soc. Am. 41 (1951)]. It's not that red will protect night vision, but destroys it much less than white.
However, red light loses its advantage with lower brightness (and I'm talking really low brightness here). If you don't need much brightness, you can get away with low intensity white [S.M. Luria and David A. Kobus, 'The Relative Effectiveness of Red and White Light for Subsequent Dark-Adaptation', Naval Submarine Medical Research Laboratory, Report 1036 (1984)]. White has the advantage of giving you sensitivity of a full color spectrum over any monochromatic source. It essentially makes no sense to restrict your eyes to the sensitivity of just one color, since you will need much higher brightness with the one color to get the same 'brightness experience' as with white.
As always, YMMV. The above articles assume 'normal' 'average' vision. If you're color-blind, for instance, your cones and rods react differently anyway, and it may not work for you.
M@elstrom said:I'm definitely no expert in ALS (Alternative Light Sources) though CPF does have it's share, my understanding was...
* Rods are our night adapted vision receptors (most sensitive to blue/green) primarily located in our peripheral optic regions, don't interpret colour OR movement
* Cones are responsible for specific detail & colour (most sensitive to red) primarily in our centered optic region
* Photosensitive ganglion cells regulate the dilation of the pupil (amongst other activities) ultimately controlling the amount of light entering the eye
Thus...
* Red promotes night vision, peripheral vision & rapid night adaption in situations devoid of ambient light.
* Green promotes detail, definition & prevents loss to our field-of-vision (night blind spot) but negates "peripheral" vision
Additional subject matter:-
Red - Night vision myth
Night vision - Wikpedia
Photoreceptor cell - Wikipedia
Nightvision in terms of Aviation application
Forensic ALS product guide - Foxfury.com
M@elstrom said:Obviously green light effects the Rod cells and to a lesser extent the Cone cells due to their 3-way cell distribution (which varies from one individual to the next) of the three types of Photopsin utilized by the Cone cells the largest proportion are sensitive to Long light Wavelengths of 500~700nm (predominantly Red).
Considering our Cone cells are responsible for detail & acuity it seems only logical that this is the reason for the NVG's applied color frequency and use of green ALS's in field for map reading and up close detail work
*Current school of thought seems to support the application of "significantly" low level white light for non-military and hunting/tracking applications allowing the engagement of both the Cones and to a lesser extent the Rod cells of the eye for night orientation/navigation as a means of avoiding the associated "night blind spot" resulting from peripheral only night adapted vision
Science IS always correct, barring human error. That's what I said. The thing about global warming is this-the fact that the earth is warming is undeniable, but whether or not it is a natural cycle is arguable. We don't have sufficient data to satisfy the scientific method about global warming yet. And then of course, there are people who argue things like "evolution is not real". But of course, this is just human error. Spitting in the face of scientific evidence does not count as science, and should be ignored.What a truly sad and skewed perspective... if science is always 100% correct why do we have members of the scientific community arguing about global warming? scientific ideology is nothing more than the current "collective agreement" reached through repeatable experiments OR interpretation of data collected using the scientific approach/method...
Remember they once thought the world was flat, the earth was at the centre of the galaxy & the atom was the smallest structure in the universe, trust your personal instincts/experience and only use "current science" as a guide :candle:
Although debating the scientific method and the evolution of human understanding of the natural world may make an interesting college course, we're terribly off-topic here. :thumbsdow
No, he didn't.Experiments conducted by G. Wald determined that the Rod cells were insensitive to wavelengths above 640nm (Red), ...
As one can see, both curves pretty much overlap above 600 nm. So, red light for night vision is just a myth. Or is it? After all, anecdotal evidence (as provided in this thread) seems to show that red IS better for night vision. Let's test it scientifically.
Something else that's interesting that most astronomers know is there is no color when star gazing. Your eyes can't detect color in very low light. Also you see less detail. However, a trick you can do is look just to the side of the object. After a while your mind will gather the image in more detail than if you were looking directly at it.
Yes, and thanks for these charts (which none of us have access to) and would you kindly do me (us) a favor and clear some things up since you can read the actual articles (I can only find brief summaries):
A) "Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors"
Liars! You only tested red vs white (going by the charts). Blue green etc never got tested.
B) "Thus red is better than white at preserving, or at least reducing the time to restoring, night vision once exposed."
How exactly was this tested? After the antagonistic light exposure were the subjects then pressing a button at the lowest level that they could reliably detect a light bulb had been turned on staring right at it? Asked to read text and getting an accuracy score of 75% or better? The submarine tests seemed to be judging the ability to see silhouettes against a starry sky, or something similar, but the other test I need more details, please.
C) "After testing the subjects ability to (lets say) read the text with a 75% accuracy level after exposure to the four test voltages (*** shown on the logarithmic scale axis X, using the white light bulb, we then repeated the test exactly but instead substituted the red light bulb.
Hello! McFly! Red light bulbs are white ones that have been painted red so they obviously will have a reduced output and yeild better results simply because they are dimmer and that you haven't accounted for! [People in this thread who claim red is superior haven't indicated they made any attempts to account for this either, I might add.]
---
Slightly off topic, but I'll bring it up anyways:
There are two kinds of people interested in red light. An astronomer wants to be able to read sky maps and find things in a bag while preserving night vision as best possible, and number two, a sniper who also wants to preserve night vision but even more so doesn't want to give away his (her) position. Isn't red light, the internationally accepted color of attention getting (think a bike light) about the stupidest color to use? Hey look at me, over here!:wave:
Low red light DOES inhibit dark adaptation. However, it does it MUCH LESS than white, or other colors. A dark adapted eye that gets low red light will recover faster back to dark adaptation than the same eye exposed to white light of comparable brightness.
People in this thread who claim red is superior haven't indicated they made any attempts to account for this either, I might add.
Nitro said:If I go inside with a white light, even if dim, it does take longer to get my night vision back than if it's red.
Oh, and about 'no color during stargazing': Sure, the rods do not detect colors. But stars ARE differently colored, and with a large enough telescope you can see those colors with your own eyes. Essentially, the objective opening diameter needs to be large enough to collect enough light. My old school had a telescope large enough -- forgot how large exactly, and unfortunately not often enough available (plus, usually lousy weather in Germany, and a lot of stray light). But once I saw Betelgeuse, and got perfect seeing. Amazing! The air between my eye and Betelgeuse would become perfectly still for just a moment, and the fuzzy blinky blob I saw did shrink to this perfect pinpoint with an amazing red-orange hue. Just beautiful.
Some stars do have discernible color,
If you mean discernible by the eye, then it just means there's enough light reaching your eye to activate the Cones.