[ QUOTE ]
gwbaltzell said:
[ QUOTE ]
UnknownVT said:
Nope, I
did mean Photopic - ie: daylight vision using the cones -
when using a flashlight there is enough light that we are using the cones vision - since we see color......
[/ QUOTE ]
I know I'm /ubbthreads/images/graemlins/dedhorse.gif, but most flashlight use would be mesopic (both rods and cones) unless starting into the working end /ubbthreads/images/graemlins/grin.gif .
Photopic (cone only) doesn't start until about 1000 cd • M^2.
[/ QUOTE ]
That's NOT much light - 1,000 cd sounds alot but that's per square metre (more than a square YARD!) - a flashlight even the
dim CMG Infinity Task light (NOT the Ultra) will produce more than that for close tasks -
Look at your own referenced article from the army and the panel on Mesopic vision says "reduces color vision and decreases visual acuity" - under white flashlight lighting unless very very dim most of us are seeing full color and clear acuity - so it IS Photopic vison we are using WITH the illumination of the flashlight.
However withOUT the flashlight we may well be using Mesopic vision - since most of us live in urban environments and with the amount of amabient light - it is very UNlikely we are using true Scotopic (night) vision.
This Army article is very similar to the USAF Flight Surgeon's article which deals a LOT more with Human Night Vision - since it is critical for pilots -
Here's a quote from
USAF Flight Surgeon's Guide: Chapter 8
(about 2/3 down the page under the heading "Night Vision")
QUOTE:
Enhancing and Maintaining Dark Adaptation: For maximum utilization of scotopic vision, 20 to 30 minutes are required, in total darkness, to attain satisfactory dark-adaptation. A more practical alternative is to have the aircrew members wear red goggles to facilitate dark adaptation. Red goggles can be worn in normal illumination and do not interfere significantly with the ability to read maps, charts, manuals, etc. They block all light except red light, and red light does not simulate the rods, as we have seen.
To understand why red filters can be used to achieve dark adaptation, it is necessary to examine the relative positions of the photopic and scotopic sensitivity curves in Figure 8-20. If a red filter with a cutoff at about 650 nanometers is worn, essentially no light is transmitted to the eye that can stimulate the rods. However, the cones are sensitive to the red light, and, thus, adequate visual acuity is permitted. By wearing red goggles for 30 minutes, the rods are almost fully dark adapted. Although the cones are not dark adapted, it only takes about 5 to 7 minutes, after a pilot steps into the dark, for the cones to adapt. Cone adaptation is relatively unimportant, since they are incapable of functioning in starlight illumination. There are, however, some drawbacks to wearing red goggles. For example, when reading maps, all markings in red ink on a white background may be invisible. In addition, red light creates or worsens near point blur in the pre-presbyopic or presbyopic pilot, as red light comes to a focus behind the retina and requires more accommodation to bring it into focus.
Dark adaptation of the rods develops rather slowly over a period of 20 to 30 minutes, but it can be lost in a second or two upon exposure to bright lights. The night flyer must, therefore, be taught to avoid bright lights. Also, the instrument panel must be kept illuminated at the lowest level consistent with safe operation, and the flyer must avoid looking at flares, after-burner flames, or gun flashes. If light must be used, it should be as dim as possible and used for the shortest possible period.
Dark adaptation is an independent process in each eye. Even though a bright light may shine in one eye, the other will retain its dark adaptation, if it is protected from the light. This is a useful bit of information, because a flyer can preserve dark adaptation in one eye by simply closing it.
Cockpit Illumination: The use of red light (wavelength greater than 650 nanometers) for illumination of the cockpit is desirable, because it, like red goggles, does not affect dark adaptation. Red cockpit lighting has been traditional since World War II. The intent was to maintain the greatest rod sensitivity possible, while still providing some illumination for central foveal vision. However, red cockpit lighting did create some near vision problems for the pre-presbyopic and presbyopic aviators. With the increased use of electronic and electro-optical devices for navigation, target detection, and night vision, the importance of the pilot's visual efficiency within the cockpit has increased and new problems have been created. Low intensity, white cockpit lighting is presently used to solve those problems. It affords a more natural visual environment within the aircraft, without degrading the color of objects. Blue-green cockpit lighting is used in aircraft in which night-vision devices are used because, unlike the human eye, these devices are not sensitive to light at that end of the visual spectrum. In addition, blue-green light is the easiest for accommodative focus and is seen by the rods more readily than any other color. It is not seen as blue-green, however, but only as light. However, the enemy can easily see a blue-green light, under scotopic conditions, in any position of his peripheral field, whereas a low intensity red light would be invisible unless viewed directly.
UNQUOTE
I hope this clarifies and confirms the use of RED light to preserve human night vision.
Green and Blue-green are primarily used for compatibility with Night Vision EQUIPMENT - with the benefit that at lower levels they are still useful for human vision.
However since they are the wavelength most sensitive to the human eye - it doesn't take much to disturb human night (scotopic) vision - in fact I would go to say that of all the mono-colors those are the WORST for
preserving human night (scotopic) vision.
(Whereas some people (including me) do have difficulties seeing well under Red light - but that difficulty does NOT negate the fact that Red is the correct color to preserve human night (scotopic) vision.)
An easy empirical evidence is the continued and persistent use of dim Red lighting in astronomy observatories...
you're very likely to be thrown out for using green or blue-green lighting -
myth or no myth......
/ubbthreads/images/graemlins/dedhorse.gif - and we can see it under red, or green/blue-green lighting /ubbthreads/images/graemlins/grin.gif
