Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 05-11-2018, 19:09   #1
cruiser

Join Date: Feb 2012
Location: Half Moon Bay, CA, USA
Boat: 1963 Pearson Ariel, Hull 75
Posts: 1,197
Blue versus red light for preserving night vision

I read on this forum an earlier post from a strong proponent of blue light for preserving night vision. As a pilot, I've been using red cockpit lighting for decades, and I know the FAA expended a lot of effort in biomedical research -- finally concluding red light was best.

So why the disagreement? I did some research and found the following three reasons for favoring red light over blue:

1) Producing dim blue light from an incandescent bulb that is dimmed by running at reduced voltage produces no blue light (in accordance with Planck's law), so in pre-LED days it was practically difficult to produce dim blue light without running an incandescent lamp at higher voltage (higher color temperature) and using a dense blue filter to make it dim.
2) The center of the human fovea, the part of the eye that you use to read printed materials and finely detailed charts, is blind to dim blue light: https://www.osapublishing.org/josa/a...t.cfm?id=75312. The rods can take over for blue-blindness in brighter light.
3) The rods, which we depend on to see dimly lit objects, are much less sensitive to red than to green or blue light. So at equal intensities dim red ambient light has much less of an effect on degrading night vision than does blue light. (Note the qualification: "at equal intensities." You don't need as much blue light to see in the dark.)

In the past, pilots had analog instruments and spent a great deal of time reading printed procedures and studying paper charts using ambient light. They needed to use the blue-blind parts of their eyes. Today, modern aircraft and boats frequently have "glass" cockpits with electronic displays with direct lighting where resolving fine details on paper are less frequently needed. Here, blue light is less of a hindrance, and producing dim blue ambient light with LEDs is easily accomplished. And since the blue cones are more sensitive than red cones, so you need less blue light than you need red to see nearby objects. If you don't need to read finely detailed charts, analog instruments and printed matter, you may be better off with blue light.


All of this assumes normal color vision. In the case of pilots, they are tested for color vision and are usually restricted no night flying if they have any color blindness. The FAA research completely disregards the night vision effects for color blind pilots.
Cpt Pat is offline   Reply With Quote
Old 05-11-2018, 19:40   #2
Registered User
 
Capt Ben's Avatar

Join Date: Dec 2012
Location: Chicago, IL
Boat: 40', Farr 38
Posts: 102
Re: Blue versus red light for preserving night vision

As I’ve installed RGBW led strip lighting over my nav station, of late, ive changed from a dim red to a dim green. First off, red marks on charts don’t disappear. Second, as I recall, 360nanometer light (green) focuses directly on the fovea where as red was either in front of or behind and so is blue.
Capt Ben is offline   Reply With Quote
Old 05-11-2018, 20:23   #3
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 12,855
Re: Blue versus red light for preserving night vision

This has been discussed many times on the forum.

Red illumination is a pain to use. It is not suitable for the rapid processing of high levels of information, but if you want to preserve the very best dark adaptation and still for example read depth numbers on a chart, or just make a cup of coffee, it is the only option.
noelex 77 is online now   Reply With Quote
Old 05-11-2018, 21:17   #4
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 12,855
Re: Blue versus red light for preserving night vision

Quote:
Originally Posted by Cpt Pat View Post
2) The center of the human fovea, the part of the eye that you use to read printed materials and finely detailed charts, is blind to dim blue light:
This would make blue light a very poor choice. The aim when preserving night vision is to use a light source that can used by our cone receptors, but is poorly seen by our rod receptors.

In simplified terms the cones are more prevalent in the centre of retina, the fovea. They are the only receptors able to see detail. We must use these receptors when trying to see any detail, for example to reading numbers.

The rod receptors are very sensitive to low levels of light. They cannot see detail and not very prevalent in the centre of retina (which is why you can see things better at night if you direct your fixation a little off to the side). However, it is these receptors that will best allow us to see a crab pot float, unlit navigation mark etc when sailing at night.

When, for example, checking a chart, the aim is to use a light that can seen by our cones, because these are the only receptors with enough resolution, but at the same time preserve and avoid bleaching out the more sensitive rods. So the ideal light is well seen by our cones but poorly seen by the rods. Red light is the best wavelength for this.
noelex 77 is online now   Reply With Quote
Old 05-11-2018, 23:34   #5
Navigator
 
SeanPatrick's Avatar

Cruisers Forum Supporter

Join Date: Dec 2012
Location: Norfolk, VA USA
Posts: 439
Re: Blue versus red light for preserving night vision

Just do what soldiers do when they have reason to believe an illumination flare is about to be set off: cover one eye. That way, no matter how bright a light you use or whatever color, you still have good night vision in at least one eye.
SeanPatrick is online now   Reply With Quote
Old 06-11-2018, 10:25   #6
Registered User

Join Date: Dec 2011
Posts: 1,414
Re: Blue versus red light for preserving night vision

They stopped putting red cockpit lighting in transport category airplanes at least fifty years ago. The first one I flew was the Boeing 727 and it had white cockpit lighting, day and night. No one has proven this debate one way or the other. The FAA still clings to a lot of myths from WWII, some of which have caused tragic accidents, like immediately pitching to V-2, or even to stick-shaker, when and engine fails on clime-out. They changed that one after the American Airlines DC-10 accident at Chicago-O'Hare.
jmschmidt is offline   Reply With Quote
Old 06-11-2018, 10:40   #7
Registered User
 
Dooglas's Avatar

Join Date: Sep 2010
Location: Oregon City, OR
Boat: 37 Uniflite Coastal Cruiser
Posts: 724
Re: Blue versus red light for preserving night vision

Old Navy salts likely remember the blue battle lights on US combat vessels during WW2. I presume this was because of the ability for the eye to note a dim blue light at distance in the dark.
Dooglas is offline   Reply With Quote
Old 06-11-2018, 10:41   #8
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 12,855
Re: Blue versus red light for preserving night vision

The requirements for flying, at least for military and commercial jets are not the same as sailing. Pilots of these aircraft need to process lots of information rapidly and this is not compatible with maintaining high levels of dark adaptation. Red illumination is often not a great choice.

Pilots are only generally expected to achieve mild/moderate levels of dark adaptation and the work environment is designed with this in mind.

When they start marking anchorages with lighting as in this photo, showing where it is safe to drop the hook, then sailors can also forget about red illumination.

Sailing at night is a bit more like trying to land after dusk when the whole runway is only illuminated by a few car headlights, if you are lucky, if not moonlight, not that I have ever done something so irresponsible
Attached Thumbnails
Click image for larger version

Name:	763AC068-F43C-4245-A71B-3DBF71FB2ABB.jpeg
Views:	647
Size:	52.0 KB
ID:	180223  
noelex 77 is online now   Reply With Quote
Old 06-11-2018, 11:00   #9
Senior Cruiser
 
newhaul's Avatar

Cruisers Forum Supporter

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 10,230
Re: Blue versus red light for preserving night vision

Using blue-green light on deck at night preserves the ability to observe white lights On other vessels at a distance.
Using red reduces the ability . Due to the different wavelengths of the various colors .
__________________
Non illigitamus carborundum
newhaul is offline   Reply With Quote
Old 06-11-2018, 11:24   #10
Registered User

Join Date: Jan 2011
Location: Holland, Michigan
Boat: Catalina 30
Posts: 193
Re: Blue versus red light for preserving night vision

My non-scientific observation is that red / orange lighting at night is NOT helpful, because often it is too bright. Better to have much lower levels of white light, or green light. Seems to me the lumens are more important than the color....just my sense of it.
carlheintz is offline   Reply With Quote
Old 06-11-2018, 11:45   #11
cruiser

Join Date: Feb 2012
Location: Half Moon Bay, CA, USA
Boat: 1963 Pearson Ariel, Hull 75
Posts: 1,197
Re: Blue versus red light for preserving night vision

Quote:
Originally Posted by noelex 77 View Post
This would make blue light a very poor choice. The aim when preserving night vision is to use a light source that can used by our cone receptors, but is poorly seen by our rod receptors.

In simplified terms the cones are more prevalent in the centre of retina, the fovea. They are the only receptors able to see detail. We must use these receptors when trying to see any detail, for example to reading numbers.

The rod receptors are very sensitive to low levels of light. They cannot see detail and not very prevalent in the centre of retina (which is why you can see things better at night if you direct your fixation a little off to the side). However, it is these receptors that will best allow us to see a crab pot float, unlit navigation mark etc when sailing at night.

When, for example, checking a chart, the aim is to use a light that can seen by our cones, because these are the only receptors with enough resolution, but at the same time preserve and avoid bleaching out the more sensitive rods. So the ideal light is well seen by our cones but poorly seen by the rods. Red light is the best wavelength for this.
All of your post above agrees with the studies I found.

On your point of not using your center of vision for detecting dim objects, anyone can verify this with an experiment at night: look away slightly from a dim object and observe it is brighter than when looking directly at the object.

I was taught to scan in 10 degree increments while shifting to the next increment every 5 seconds - the width of your fist held at arm's length is a good guide for 10 degrees of arc - while doing this, focus your attention on both sides of your center of vision. Don't be surprised if the object vanishes when you look directly at it.
Cpt Pat is offline   Reply With Quote
Old 06-11-2018, 11:55   #12
cruiser

Join Date: Feb 2012
Location: Half Moon Bay, CA, USA
Boat: 1963 Pearson Ariel, Hull 75
Posts: 1,197
Re: Blue versus red light for preserving night vision

Quote:
Originally Posted by jmschmidt View Post
They stopped putting red cockpit lighting in transport category airplanes at least fifty years ago. The first one I flew was the Boeing 727 and it had white cockpit lighting, day and night. No one has proven this debate one way or the other. The FAA still clings to a lot of myths from WWII, some of which have caused tragic accidents, like immediately pitching to V-2, or even to stick-shaker, when and engine fails on clime-out. They changed that one after the American Airlines DC-10 accident at Chicago-O'Hare.
Yes, I remember that accident. The DC-10 literally "lost" an engine: it fell off. If the pilot hadn't followed procedure, and instead lowered the nose and angle of attack, he may have been able save the aircraft.
Cpt Pat is offline   Reply With Quote
Old 06-11-2018, 11:59   #13
cruiser

Join Date: Feb 2012
Location: Half Moon Bay, CA, USA
Boat: 1963 Pearson Ariel, Hull 75
Posts: 1,197
Re: Blue versus red light for preserving night vision

Quote:
Originally Posted by SeanPatrick View Post
Just do what soldiers do when they have reason to believe an illumination flare is about to be set off: cover one eye. That way, no matter how bright a light you use or whatever color, you still have good night vision in at least one eye.
Yes, it's a useful procedure.

Imagine how salty one would look using a black patch over one eye to accomplish this!
Cpt Pat is offline   Reply With Quote
Old 06-11-2018, 12:06   #14
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Boat: Bestevaer.
Posts: 12,855
Re: Blue versus red light for preserving night vision

Quote:
Originally Posted by Cpt Pat View Post
I was taught to scan in 10 degree increments while shifting to the next increment every 5 seconds - the width of your fist held at arm's length is a good guide for 10 degrees of arc - while doing this, focus your attention on both sides of your center of vision. Don't be surprised if the object vanishes when you look directly at it.
This is a good technique when reasonably dark adapted. The other option to scan the horizon is to keep your fixation about 10°-20° below, or above the actual horizon. This will put any vessel, mark etc that is on the horizon in the zone where the rod concentration is highest which is about 10°-20° away from the fixation point.
noelex 77 is online now   Reply With Quote
Old 06-11-2018, 13:22   #15
Marine Service Provider

Join Date: May 2011
Location: PDX
Boat: Gulfstar 50
Posts: 1,978
Re: Blue versus red light for preserving night vision

Take a look at this chart of rod and cone sensitivities. You can see that if you use a red light at greater than 600 nm or so you are in the peak of the red cone sensitivity and no blue or rod sensitivity. The idea for red light is that the red cones get their sensitivity decreased while keeping full sensitivity in blue and rods.

The problem with red lights in the past was that they were not monochromatic. Thus even a dim red light would deplete the sensitivity of blue cones and rods as well as green cones.

Typically red led are around 630 nm or 660 nm. (nano-meters)

One other theory for keeping night vision is to use a low level blue-green light in the 520 nm range. This is the area of the maximum sensitivity of the eye and thus very low levels of light give "good" vision while not decreasing the sensitivity of the eye too much.

You pays your money and takes your chances
Attached Thumbnails
Click image for larger version

Name:	1416_Color_Sensitivity.jpg
Views:	422
Size:	388.3 KB
ID:	180228  
evm1024 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FLIR Night Vision versus dated Raymarine rader Wolfgang6 Marine Electronics 18 07-07-2019 09:05
Yanmar SB8 versus repower, versus more space and a larger outboard? SailingFan Engines and Propulsion Systems 46 01-09-2017 17:47
Boston Whaler versus Albury versus ??? Magor Powered Boats 3 26-02-2014 12:43
Colour of Light for Best Night Vision Lars_L Electrical: Batteries, Generators & Solar 37 11-09-2011 12:49
WTB: ITT Night Mariner 160 night vision monocular sporf Classifieds Archive 0 17-11-2008 18:53

Advertise Here


All times are GMT -7. The time now is 05:07.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.