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Do you think red light preserves your night vision?


palebluedot

Does red light preserve your night vision?  

37 members have voted

  1. 1. Does red light preserve your night vision?

    • Yes
      29
    • No
      8


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I have always gone along with the general belief that seeing in red light will not cause your pupils to contract as much as it would if all the other wavelengths were let in to the eye. However, there appears to be a lot of people who disagree.

So, is red light better? It appears to be a requirement at star parties. If it's not, why bother?

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No, simply because a bright red light will still wreck night vision, it needs to be a dull red light directed away from eyes.

The red lights in my obsy are too bright for observing, but as i dont do any its not a problem :glasses2:

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While red light isn't all that it's cracked up to be for preserving night vision, it is the type of illumination that is recommended in almost all cases where night vision is important, and is a darn sight better than having someone shine a brilliant, white light directly into your face !

However, since the eye appears to be more sensitive to green light ( think of the green lasers or "night vision" glasses ) I have often wondered if a dim green light wouldn't be easier to read a star map by? Just curious

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Find that I still have to readjust by about the same amount of time after a red light hits me as with a white light.

Do wonder if people use brighter red lights to compensate for the removal of the other wavelengths. As in they can use a 1/2 watt LED if white but need a 1 Watt LED if red. Also they may pick a brighter one as the belief is that they do less/no harm so select a big bright red light.

Would have thought that a green one was better, thats what the eye is most sensative to so would need less light to see by.

Suspect red was used for some reason at some time and got tagged as being the colour for night vison. Why do submarine filmss have a red light in them for instance?

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A major player in the night vision adventure is rhodopsin, the chemical that allows the rods in your eye to perceive shades of gray.

Color vision, and what we rely on for our daytime seeing, is the province of the cone cells in the center of the eye. But it takes a certain level of intensity for their function. Sunlight, and artificial light, provide sufficient illumination in day time for our life activities. But, we need less sleep than there is darkness at night, in general, so there we are in our diurnal existence. Thus, providing us some survival benefits at night, are the rod cells around the outer fringe. At night we are in need of motion detection for survival. We need to detect the bear or wolf sneaking up, without need of telling the color of its eyes. So, the rod cells around our eye margin gives us some shape and motion detection without fine detail. We take advantage of this through averted vision (averted imagination, my non-astronomy friends tell me), where low light level detail is detected around the edge of the field of view while the cones around the center of the field need more illumination to function.

But the rods don't work on their own. They require "visual purple", or rhodopsin, in the eye fluid to function. When darkness settles in, our pupils open fairly quickly, on the order of seconds. But it takes around 20 minutes, to as long as 40 minutes, for the body to produce enough rhodopsin to fire up the rods. THAT'S night vision. The weak point of it all is that visual purple is photoreactive; a few seconds of bright light, especially in the green to blue end of the spectrum, and rhodopsin breaks down and is no longer present. It needs to be remanufactured. Start the cycle again.

Interestingly, pure red light does not seem to trip the breakdown. Two companion conditions must be stressed along with the red insensitivity. It is very difficult, to generate pure red; some shorter wavelengths creep in. Second, the intensity, as mentioned above, is also critical. The pupil will react independently of the rhodopsin, and will start to close down. So, dim red lights where lighting is needed is important. In fact, you can detect motion in security situations somewhat better with diffuse red light than these direct airplane landing light beacons some folks use for outdoor lighting.

The International Dark Sky Association has many teaching aids to demonstrate the "less is more" concept.

So, sure, red light is better for maintaining night vision, within the limits of understanding that intensity is also important. Must maintain that rhodopsin level! But, remember that detection is not detail, and for pattern discrimination such as priniting on paper, your rods are not built for nearly the detail that cones are, and that takes a bit of illumination. Or shading contrast.

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I find red light better than white light of course but it's the intensity that's important. muted red light is best if required - I tend to use maps and a notebook so it's pretty essential but I rarely look right at the light.

I've ticked yes in the poll.

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In my humble opinion, red is better than regular light and I have seen this difference especially when using Stellarium.

Isabelle

LCD's with FLUORESCENT back lighting is not red, in fact it is blue no?

LED back-lighting; I am not sure what end of the colour spectrum that emits.

This is why one gets fatigue when watch TV or a Fluorescent backlit screen (or lighting) and takes longer to get to sleep after watching TV/Monitors.

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The question reminds me of the days I used to print photos in my darkroom. For some papers a red safelight was used, but other required a different coloured safelight. From what I recall, multigrade paper needed a safelight that was almost a kind of dark brown colour. Maybe, that would be a better option for our night vision? That's not to say that red is necessarily bad, just that other options might be better.

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I am aware that the red light is ideal - even with very dim red light your eye gets the best possible contrast for reading for instance star maps than with any other colour in the light spectrum. Small wonder that emergency cut-out lights are usually red. Ever noticed the poor contrast you get in clubs with very fashionable blue ambient lighting? It is often eye tiring.

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