Ross D
Well-Known Member
The light from coloured LEDs is more or less one wavelength the photons are emitted at one energy and hence wavelength dependent on the LED. The white ones are multi coloured which are blend to make the shades of white.
chart table red light....any suggestions?
- Thread starter Matata
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noelex
Well-Known Member
Our Scotopic (night vision) only has low resolution and is not capable of most detailed tasks such as reading charts or instruments for this we need or photopic (bright light) vision. The aim of using red light is to use our detailed photopic vision, but at the same time preserving our scotopic vision. This is possible because our scotopic vision is insensitive to red light.
The aim is to use our good acuity photopic vision when essential without destroying our scotopic vision which may be needed when we have finished the detailed task.
If you use even a dim torch you are using your photopic system to see. If the torch is long wavelenth red you can go back to your scotopic vision when the torch is turned off. If the torch is a white light your scotopic system will take many mins to recover.
The white torch is more pleasant to use and provides normal colour vision, but it is important to recognize that these benefits come at the cost of bleaching or scotopic system.
(Note:I have simplified the technical details by avoiding a discussion of mesopic vision. This simplification does not impact on the conclusions)
noelex
Well-Known Member
Personally I have found that Orange lights are the best, my last boat had this colour fitted not only for chart work but seconary cabin lights, So pleasing to the eye that I used to use them most of the time. The fittings came from low voltage systems one sees in warden controlled accomodation alarm boxes.
Just another slant on what one prefers.
Red light is harsh, monocromatic and unnatural, but it does preserve night vision. I think some posts are discussing the light they find most pleasant use at night (for me that’s a dull white light) and confusing this with the light that preserves night vision best (red light).
On night watches, with the limited crew on a yacht, I prefer function over comfort. At other times, such as at anchor, I will use a more comfortable light
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CharlesSwallow
Well-Known Member
Hi Noelex
rather than get involved in a technical debate and work my way through pages of heavy stuff outwith my direct experience, I've arranged for a response from the UK Hydrographic Office, which is local to me.
I always value professional knowledge, but the conflicting views both here and on the web about red/green/white light and night vision give me concern that there has been a lack of rigour, a reliance on out-of-date practice and hearsay, and some unwillingness to revisit traditional positions. (I exclude yourself from these last comments, as you clearly have professional knowledge.)
As soon as I have a formal reply I will post it, as I am as keen as anyone to ensure that my fading powers of accommodation and adaptation are not hindered by a less than desirable lighting system on board.
It would be encouraging to feel that we may, by robust debate, be providing a small advance in best practice for our chosen area of recreation.
Perhaps as Csail has suggested, we should all be wearing a piratical eye patch when sailing at night.
I'm sure that your friends are great mapmakers but what qualifications do they actually have in optometry and human eye physiology?
Chas
alan_d
Well-Known Member
I cannot allow everyone to think I am some sort of unlettered savant.
I was taught visual physiology about 40 years ago, and around the same time I had a particular interest in colour perception as I was involved in stage lighting. I have a copy of Gregory's Eye and Brain (dated 1966), and I also remember some relevant bits from Tomorrow's World and Horizon TV programmes, from the days when such programmes contained facts.
As a natural sceptic I was ready to accept the "Red Myth" revisionism, which seemed plausible, so I was surprised by and initially doubtful about noelex's first post in this thread, hence my request for more information.
Robin
Well-Known Member
In reality however..
I have always enjoyed night sailing and had good night vision and early on was very keen not to do anything to spoil that, hence had red lighting below decks. On later boats however we had a variety of instruments over the companionway which at night were back lit with white light. Later still and we had more instruments and even a chart plotter in the cockpit, also back lit in white just dimmed to choice. Down below at the chart table whilst we still had an ability to use red lighting there seemed little point as it would have to compete with the radar (we have had 3 varieties over the years, two CRTs with green dimmable displays and one LCD with bluey grey and white back lighting) and the chart plotters again with white back lighting. Then again even the Nav lights conspire to spoil night vision unless running on a masthead tricolour, wores of course when motoring with a steaming light on as well.
So how much does it really matter?
I have always been very careful to retain my night vision when it was needed, like entering a harbour or anchorage without the need for searchlight torches waved around manically as some do. I recognise the fact that once I have been forced to use the cordless 1 million candlepower steamer scarer to find say a mooring buoy in a strange spot on the darkest night that is it for night vision for 20 minutes, so once started in mastermind fashion I have to finish. Out at sea however it is perfectly feasible to choose the time to go below and do chart work or to judge the time to check the fine tune sail trim, done usually in later years with a dim headlight or small maglite.
It is of course quite 'cool' to have a red glow from below to show the world some ocean crossing cred.
I have always enjoyed night sailing and had good night vision and early on was very keen not to do anything to spoil that, hence had red lighting below decks. On later boats however we had a variety of instruments over the companionway which at night were back lit with white light. Later still and we had more instruments and even a chart plotter in the cockpit, also back lit in white just dimmed to choice. Down below at the chart table whilst we still had an ability to use red lighting there seemed little point as it would have to compete with the radar (we have had 3 varieties over the years, two CRTs with green dimmable displays and one LCD with bluey grey and white back lighting) and the chart plotters again with white back lighting. Then again even the Nav lights conspire to spoil night vision unless running on a masthead tricolour, wores of course when motoring with a steaming light on as well.
So how much does it really matter?
I have always been very careful to retain my night vision when it was needed, like entering a harbour or anchorage without the need for searchlight torches waved around manically as some do. I recognise the fact that once I have been forced to use the cordless 1 million candlepower steamer scarer to find say a mooring buoy in a strange spot on the darkest night that is it for night vision for 20 minutes, so once started in mastermind fashion I have to finish. Out at sea however it is perfectly feasible to choose the time to go below and do chart work or to judge the time to check the fine tune sail trim, done usually in later years with a dim headlight or small maglite.
It is of course quite 'cool' to have a red glow from below to show the world some ocean crossing cred.
Crabman
Well-Known Member
I use blue not red and it works for me.Replacement bulbs on ebay.
noelex
Well-Known Member
I have always enjoyed night sailing and had good night vision and early on was very keen not to do anything to spoil that, hence had red lighting below decks. On later boats however we had a variety of instruments over the companionway which at night were back lit with white light. Later still and we had more instruments and even a chart plotter in the cockpit, also back lit in white just dimmed to choice. Down below at the chart table whilst we still had an ability to use red lighting there seemed little point as it would have to compete with the radar (we have had 3 varieties over the years, two CRTs with green dimmable displays and one LCD with bluey grey and white back lighting) and the chart plotters again with white back lighting. Then again even the Nav lights conspire to spoil night vision unless running on a masthead tricolour, wores of course when motoring with a steaming light on as well.
So how much does it really matter?
I have always been very careful to retain my night vision when it was needed, like entering a harbour or anchorage without the need for searchlight torches waved around manically as some do. I recognise the fact that once I have been forced to use the cordless 1 million candlepower steamer scarer to find say a mooring buoy in a strange spot on the darkest night that is it for night vision for 20 minutes, so once started in mastermind fashion I have to finish. Out at sea however it is perfectly feasible to choose the time to go below and do chart work or to judge the time to check the fine tune sail trim, done usually in later years with a dim headlight or small maglite.
It is of course quite 'cool' to have a red glow from below to show the world some ocean crossing cred.
With this kind of setup, although you will have some dark adaption with your photopic system, you are probably not using your scotopic vision at all. So red lighting would not be of any benefit.
It is a common problem. Large LCD screens are difficult to dim although the "night" setting usually helps.
You need to weigh up if the information from the radar and chartplotters outweighs the loss of night vision using these screens entails.
On my own boat in coming into a difficult anchorage at night I am at the helm with the radar and my wife retains her dark adaptation (often at the bow) to spot things that do not show up on the radar. On a night watch if the radar is running and dark adaptation is important, I only look at the screen with one eye closed.
sarabande
Well-Known Member
UKHP replies .....
I have had a reply from the UKHO Chart Operations Standards Team to my enquiry about the 'best' light for reading Admiralty charts.
" UKHO is well aware of the effects of different types of lighting on the ability to read paper charts. But in practice, as varying lights are in use in vessels worldwide over which UKHO has no control, UKHO's research has mainly been from the perspective of choosing chart colours which will be visible under typical low intensity bridge lights, rather than your specific enquiry of assessing what colours of light are best for viewing a chart.
The brighter and whiter the light (i.e. the closer to replicating full daylight conditions), the easier the chart will be to read. However, bright bridge lights impair night vision, so subdued lighting is necessary on the bridge. White light is usually avoided, due to perceived increased impairment. The typical preferred lighting was judged to be red, particularly by a significant user of our charts, the Royal Navy. But all coloured lights will affect perception in some way. When magenta was being introduced into the standard chart colour scheme, experiments showed that it tended to ‘disappear’ under red bridge lights, so some black was added to the magenta ink specification on Admiralty charts to compensate (i.e. to ‘strengthen’ the colour); this is why the 'magenta' colour on Admiralty charts is now darker than on most other nations' charts and is actually closer to purple. Whilst this presents a clearer portrayal in subdued light conditions, it may sometimes have an adverse effect as clashes of chart detail, respectively printed in black and magenta, can be more difficult to distinguish. In summary, the best lighting for reading the chart (and other documents on the bridge) whilst retaining night vision is always a compromise.
To further complicate the picture, some nations have introduced additional colours on their charts. Partly because of arrangements with other hydrographic offices for reproducing foreign charts into the Admiralty series, and partly because of increasing clutter of information on charts, UKHO has just begun introducing additional colours on selected Admiralty charts.
Accordingly, we have been careful to choose a colour palette which should be visible under bridge lights which contain at least an element of white in the make up. Under any purely red bridge lights, some colours may ‘disappear’.
As we produce increasing numbers of 'multicoloured' charts, we would welcome any feedback on readability under all types of bridge lights noting that, in recent times, more attention has been given to studies on the colour palettes and vision settings for ECDIS screens rather than paper charts.
[...]
"
So, from the world's leading chart designer and printer, you have direct advice. All red colour makes some details disappear. Charts are best read in subdued light with some white in it.
Now back to the MCA to garner their views
I have had a reply from the UKHO Chart Operations Standards Team to my enquiry about the 'best' light for reading Admiralty charts.
" UKHO is well aware of the effects of different types of lighting on the ability to read paper charts. But in practice, as varying lights are in use in vessels worldwide over which UKHO has no control, UKHO's research has mainly been from the perspective of choosing chart colours which will be visible under typical low intensity bridge lights, rather than your specific enquiry of assessing what colours of light are best for viewing a chart.
The brighter and whiter the light (i.e. the closer to replicating full daylight conditions), the easier the chart will be to read. However, bright bridge lights impair night vision, so subdued lighting is necessary on the bridge. White light is usually avoided, due to perceived increased impairment. The typical preferred lighting was judged to be red, particularly by a significant user of our charts, the Royal Navy. But all coloured lights will affect perception in some way. When magenta was being introduced into the standard chart colour scheme, experiments showed that it tended to ‘disappear’ under red bridge lights, so some black was added to the magenta ink specification on Admiralty charts to compensate (i.e. to ‘strengthen’ the colour); this is why the 'magenta' colour on Admiralty charts is now darker than on most other nations' charts and is actually closer to purple. Whilst this presents a clearer portrayal in subdued light conditions, it may sometimes have an adverse effect as clashes of chart detail, respectively printed in black and magenta, can be more difficult to distinguish. In summary, the best lighting for reading the chart (and other documents on the bridge) whilst retaining night vision is always a compromise.
To further complicate the picture, some nations have introduced additional colours on their charts. Partly because of arrangements with other hydrographic offices for reproducing foreign charts into the Admiralty series, and partly because of increasing clutter of information on charts, UKHO has just begun introducing additional colours on selected Admiralty charts.
Accordingly, we have been careful to choose a colour palette which should be visible under bridge lights which contain at least an element of white in the make up. Under any purely red bridge lights, some colours may ‘disappear’.
As we produce increasing numbers of 'multicoloured' charts, we would welcome any feedback on readability under all types of bridge lights noting that, in recent times, more attention has been given to studies on the colour palettes and vision settings for ECDIS screens rather than paper charts.
[...]
"
So, from the world's leading chart designer and printer, you have direct advice. All red colour makes some details disappear. Charts are best read in subdued light with some white in it.
Now back to the MCA to garner their views
PetiteFleur
Well-Known Member
I also no longer use my red LED light - fitted about three years ago but on my first night trip just after the new Sunk 'roundabout' was created, all the magenta lines dissapeared! Fortunately I'd still left my white light so continued.
Never used the red light since.
BrendanS
Well-Known Member
Took me ages to find it, but in a previous discussion on the subject over 3 years ago, I posted this interesting article
http://stlplaces.com/night_vision_red_myth/
http://stlplaces.com/night_vision_red_myth/
alan_d
Well-Known Member
Oh dear.
Your time would have been better spent reading the thread before posting; see posts 3, 10 and several subsequently.
Waterdog
New Member
If you don't fancy bits of red plastic or nail varnish I know that Labcraft make exactly this with a flexible arm and red rotating filter etc. they call it the Adjustalamp. Seems to work just fine, though it did cost £16. I got mine online from Boat Electricals but I'm sure lots of others will stock it too.