Red light myth that's not a myth.

[Gsailor]

I have read a few posts upon this... an excellent one posted by an ophthalmologist.

Red light (because of cones and rods) allows us to keep our night vision.

BUT does the intensity or brightness of the red light make a difference?

My thinking says "no".

If a red light wavelength maintains night vision, then a really bright red light should make no difference (except let the petson see more) to night vision.

Am I correct or talking rubbish?

 

[noelex]

You are correct, it is not a myth. Red light is better at preserving the maximum levels of dark adaptation. This is because rods are relatively insensitive to far red light.

Unfortunately rods can still register and therefore be bleached by red light.

So it is still helpful to reduce the illumination when using red light, although this not as critical as it is with white light.

 

[simonfraser]

rods are most sensitive to wavelengths of light around 498 nm (green-blue), and insensitive to wavelengths longer than about 640 nm (red)
so as long as your red lights are only emitting above 640nm you keep your night vision, just need to appropriate LED / filters

 

[Halo]

My experience is that using night vision is much better with practice. If you use it regularly then you seem to be able to recover from light exposure much quicker.
How do I practice? No lights when getting up for a pee in the night!!!

 

[bikedaft]

I did look at the original research once, there is really only one paper, from early WW2. It has much more to do with light intensity, than colour, although red was slightly better, and hence red it has been ever since...

 

[johnalison]

As I understand it, none of the receptors respond to red light, with the longest wavelengths sensed being in the yellow-orange range, with red photons not carrying enough energy. The sensation of red is created from the absence of blue. Colour is due to cones of course, but I don’t think rods will sense red either. The brightness factor probably comes down to whether the red light is monochromatic or contains light that rods respond to. In any case, it seems sensible to keep light levels to a minimum.

 

[GHA]

Very often better to ask https://chat.openai.com/ than on here nowadays--

is red light backlight for instruments better at preserving night vision on ships and planes. include citation to science papers

Yes, red light backlight for instruments is better at preserving night vision on ships and planes. This is because the human eye is less sensitive to red light, allowing the eye to remain adapted to low light conditions while still being able to read the instruments.
There are several studies that have investigated the effect of red light on night vision. One such study is "Night Vision: An Overview" by J. Vernon Odom, which was published in the journal Aviation, Space, and Environmental Medicine in 1983. In this study, Odom explains that red light is preferable for night vision because it does not affect the rhodopsin in the rods of the eye, which is responsible for low-light vision.
Another study, "Color and luminance in aviation lighting: A review of recent research" by John A. Caldwell, was published in the journal Applied Ergonomics in 1992. Caldwell's study found that red light was the most effective color for preserving night vision, and that it was important to use the lowest possible luminance to minimize the risk of glare.
In addition, the Federal Aviation Administration (FAA) recommends the use of red light for night operations in its Advisory Circular 20-30B, which provides guidance for aircraft lighting. The FAA states that "red lighting is preferred for instrument panel illumination during night operations because it preserves the pilot's night vision."
Overall, the scientific literature and aviation industry guidelines support the use of red light backlight for instruments to preserve night vision on ships and planes.

 

[Refueler]

As an ex OOW from ships ... Red lights were fitted in Chart rooms and at chart tables when all in one bridge area. For many - it was a filter that could be clipped to the standard chart light. A lot of ships - finding the filter was hardest part.

Was it better ... only marginally. In fact many ships did away with it later.

Interesting snippet : Anyone know why the Medical Section of the Int Code of Signals book is green pages ?

Its 2 reasons :

Its supposed to be easier to read in red light conditions
and
To open direct to the section by way of seeing the colour.

 

[Trident]

Many military and civilians applications are moving to blue light for night if reading is required; the reason is that you can have much dimmer blue light and still read (maps, charts, medical notes etc) so your night vision is left more able to recover than the brighter red light needed to read in at night.

 

[capnsensible]

Many military and civilians applications are moving to blue light for night if reading is required; the reason is that you can have much dimmer blue light and still read (maps, charts, medical notes etc) so your night vision is left more able to recover than the brighter red light needed to read in at night.

Did some trials on control room blue lighting. Red was found to be better. Can imagine some of the trial reports had subjective comments from those involved, but I was happy we retained red lighting.

 

[geem]

Many military and civilians applications are moving to blue light for night if reading is required; the reason is that you can have much dimmer blue light and still read (maps, charts, medical notes etc) so your night vision is left more able to recover than the brighter red light needed to read in at night.

Friends use green light. Seem to work as well as red light for night vision.

 

[noelex]

Friends use green light. Seem to work as well as red light for night vision.

Green is not a good alternative on a sailboat where there are situations when the deepest levels of dark adaptation are needed.

In situations where only mild levels of dark adaption are practical the colour of light makes little difference to the level of dark adaptation. It is impossible to convey large amounts of complex data using dim red light and red light is unpleasant and difficult to use so it is a poor choice when this a requirement.

If you are well dark adapted on a night passage and want to read instruments or make a cup of coffee red light is significantly better than any other colour.

 

[bikedaft]

Don't forget shut one eye when turning on e.g. a chartplotter/phone/light. Pirates had eyepatches for a reason...

 

[geem]

Green is not a good alternative on a sailboat where there are situations when the deepest levels of dark adaptation are needed.

In situations where only mild levels of dark adaption are practical the colour of light makes little difference to the level of dark adaptation. As red light is unpleasant and difficult to use it is a poor choice.

If you are well dark adapted on a night passage and want to read instruments or make a cup of coffee red light is significantly better than any other colour.

I don't disagree but: quote
It is generally considered that red breaks down rhodopsin more slowly and, if preserving night vision is the main objective, red is better. But green light penetrates a little better, and shows more detail. It may be preferred for distance vision, and for close up clarity, such as reading instruments or maps

 

[Boathook]

Before the chart plotter .....
I tried a red light at the chart table. Changed it to a 'dim' white one as the red seemed to make if difficult to make out features on the chart. I also set the light up so that I couldn't see the light directly which also made a big difference.

 

[Refueler]

Before the chart plotter .....
I tried a red light at the chart table. Changed it to a 'dim' white one as the red seemed to make if difficult to make out features on the chart. I also set the light up so that I couldn't see the light directly which also made a big difference.

Problem is that when you use any colour other than a white light - you will lose various details of what you are looking at because of their colour ...

 

[noelex]

I don't disagree but: quote
It is generally considered that red breaks down rhodopsin more slowly and, if preserving night vision is the main objective, red is better. But green light penetrates a little better, and shows more detail. It may be preferred for distance vision, and for close up clarity, such as reading instruments or maps

Yes, there is a limit to the amount of data that can be processed using dim red light. This is part of the reason why some modern military aircraft have switched away from using red, at least as the only option. If an operator is using radar and other methods to rapidly analyse data such as whether or not a missile is going to strike, he is generally better to sacrifice some night vision in order to process the complex information as quickly and as accurately as possible.

On a yacht things happen more slowly and the amount of complex data available or needed is limited. In many situations preserving the best night vision by using red light is far preferable, especially if all you want to do is make coffee.

However, this not. always the case. If you want to study the pilot book and the map/radar in detail before entering a harbour you may be better switching to white light. If this done keep in mind it take in order of 30 mins to regain your deepest levels of dark adaption, although some degree of dark adaptation will gained more rapidly.

So yachts are best equipped with a combination of red and white light with a dimming function.

 

[Fr J Hackett]

A case of spare the rod and spoil the vision perhaps.

 

[geem]

Yes, there is a limit to the amount of data that can be processed using dim red light. This is part of the reason why some modern military aircraft have switched away from using red, at least as the only option. If an operator is using radar and other methods to rapidly analyse data such as whether or not a missile is going to strike, he is generally better to sacrifice some night vision in order to process the complex information as quickly and as accurately as possible.

On a yacht things happen more slowly and the amount of complex data available or needed is limited. In many situations preserving the best night vision by using red light is far preferable, especially if all you want to do is make coffee.

However, this not. always the case. If you want to study the pilot book and the map/radar in detail before entering a harbour you may be better switching to white light. If this done keep in mind it take in order of 30 mins to regain your deepest levels of dark adaption, although some degree of dark adaptation will gained more rapidly.

So yachts are best equipped with a combination of red and white light with a dimming function.

I find reading charts with red light impossible. I am going to try a green led bulb and see how that works. My pal says he finds it better than red for detail without the loss of night vission if you switch on the white light. We have red lights everywhere down below that allow us to get to the heads and make tea in the galley etc. I have no problem with this and they work well except reading charts at the nav station

 

[noelex]

I find reading charts with red light impossible. I am going to try a green led bulb and see how that works. My pal says he finds it better than red for detail without the loss of night vission if you switch on the white light. We have red lights everywhere down below that allow us to get to the heads and make tea in the galley etc. I have no problem with this and they work well except reading charts at the nav station

It is your boat so obviously your choice, but the relative (not absolute) sensitivity of the rods and cones is almost equal when using green light. You missing out on the advantages of red illumination.

Monochromatic light of any wavelength makes colour coded information on charts more difficult or impossible to distinguish. If you are going to give up the advantages of red illumination you might as well use dull white light. If you keep the white light dull enough you will retain some cone adaptation although the rods will be totally bleached out.

Using red light to read charts is not pleasant and can sometimes lead to mistakes so there is nothing wrong with using dull white light if you need to study the chart in detail. However, try to avoid using white light every time you are just glancing at the chart, or if you do at least make a conscious decision if the cost in reduced dark adaption is worthwhile.

Red light in the heads and galley is a big help.