More on Flashlights and Night Vision

Today’s post is actually a comment make by C.E. Harris on yesterdays post on flashlights.  It provides a lot of additional information on flashlights and night vision. The Fenix flashlight I have on my keychain is the Fenix E01, the same one he refers to.


If you’ve ever had to find your way out of a building when the power goes out you can appreciate the value of having at least a small light with you as EDC. When working SAR or damage assessment a head lamp which provides hands-free search capability and overnight battery life without a change is a plus.

A small keychain light such as a Fenix E01 on your zipper pull or keyring is a great backup light. has my review:

Backup Light for Personal Survival Kit – Ed West Virginia December 11, 2012

I picked up several of these as replacements for the discontinued CMG Infinity Task Light. The original CMG was machined from solid aluminum, took a single AA and gave 8 lux for 20 hours. The Fenix E01 gives similar performance and is of the same rugged, machined solid aluminum, gasketed construction, but is much smaller, using a single AAA battery. Light output in side-by-side comparison is better than tiny coin-battery keychain lights, or the current single AA Gerber, which is constructed of mechanical tubing, not machined solid aluminum and therefore less rugged than the original CMG which you cannot get anymore. The Fenix is a worthy replacement which fits into an Altoids tin with your personal survival kit, or to wear around your neck as a backup light for everyday carry. It is perfect for finding small items in the cockpit, glovebox or pack at night. It is inexpensive and small enough that you can put one on the zipper pull of every outer garment, on your key ring, in your PSK and to wear around your neck all the time. When the lights go out it is enough light to find your way down exit stairways to get out of a darkened building safely. It is safer than candles for kids and women to use during the storm. AAAs are inexpensive and available everywhere. Get a bunch of these!

I have the single-AAA E01 LED lights on the zipper pulls of all garments, and carry one on my key ring all the time. They are superior to coin-battery keychain lights. AAA batteries can be found anywhere. Performance is similar to the original CMG Infinity Task Light (pre-Gerber) which uses a single AA, but is no longer available. The Gerber light is assembled from cheap mechanical tubing, not machined from a solid bar aluminum bar stock and is a poor substitute in terms of ruggedness.

I also carry as EDC a Surefire E1B Backup. This light is about the size of a cigar butt and has two power levels. Run time is 1.3 hours at 80 lumens or 37 hours at 5 lumens.

LED lights are more rugged than Xenon bulbs if dropped, and usually have a long enough burn time for one set of batteries to last overnight on a 12-hour shift, which is important. With incandescent Xenon lamps you must carry both spare lamps and spare batteries.

My needs are less for target intimidation and identification and more for trail illumination and building searches. Here we teach that in the civilian CCW role having a weapon-mounted light violates the basic safety rule of not sweeping your muzzle past anything you don’t want to shoot. If you are waving a light on your weapon it may draw fire and give the bad guys something to shoot at, so I would prefer to use a light extended away my body, as I was taught at FBI National Academy many years ago.

Back in the stone age when the US Navy flew T28 Trojans with 8-cylinder radial engines for Basic Instrument Trainers we were issued a simple 2-AA cell pen light with white bulb and sliding red filter for night cockpit use. This was used mostly for writing ADC clearances on the kneeboard for night ops, but we were trained to use it an evasion night light in denied areas also. These days a Petzl headlamp with red filter is a good choice for cockpit use in general aviation during night ops, on its lowest setting, and also as an E&E trail illuminator.

When I took my jungle survival training ion the Navy 1970s an “evasion light” was no light at all, but using your own night vision, and only when necessary as little light as possible exposed for no longer than absolutely necessary. In “Indian County” you don’t want anything which can be spotted at a distance. You must depend on staying quiet and still until your eyes are fully dark adapted, then move slowly, quietly and cautiously, traveling only at night to avoid detection and hiding under debris during the day. Movement attracts the eye, and so does any light. A moving light at night especially draws attention and gets investigated. Even a tiny LED is highly visible for a mile or more with the naked eye and several times that with FLIR or NVG.

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If you incautiously leave a light on unprotected for more than a few seconds and move around you will be seen, rapidly intercepted and caught or killed by the enemy. Side shields are necessary for military any evasion light.

For deployed personnel I recommend for evasion purposes I would consider a night vision monocular as is sold to civil aviators: see also

ALWAYS wear protective safety glasses with side guards when moving around in the bush at night!

The human eye performs poorly at night. Fatigue experienced by evaders has great influence at night. The retina is the first and fastest part of the body to react to reduction of blood oxygen. Cigarette smokers start out with an immediate night vision problem. Complete night adaptation of the eye to darkness takes over 30 minutes and can be destroyed in seconds by a muzzle flash in your face. If you MUST shoot and scoot to create a window for escape, a low-powered handgun, such as a High Standard HD Military .22 pistol with suppressor, reduces noise AND FLASH signature.

The cones used for color vision are centered in the eye but are slow to adapt and then only by a factor of x 100. Rods make it so we can see at night but not in color and are spread to the sides in the back of the eye. They are more sensitive at night by a factor of x 100,000. Rods take 30 minutes to recover from a bright light shock.

The oval shaped region retinal blind spot cannot see light, but binocular vision compensates for this in daytime. At night we often are unable to see objects if we look directly at them.

To see at night do not look look directly at what you want to see because your central vision is inoperative at night.. Looking off center at night uses your peripheral vision which is 100,000 times more sensitive than central vision at night.

Your eyes can be adapted to night vision by wearing red glasses, patching one eye and using dimmed lighting.

No matter how well you do this one muzzle flash or mortar burst in your face destroys it all. Life isn’t fair.

Your visual adaptability to light/darkness is reduced 50% every eleven years of your life. Experience and frequency of night flight is the best compensation for this loss. Any bright light effectively reduces night vision. You might try protecting one eye from light until airborne. Try wearing sunglasses at dusk.

The use of colors other than red in the cockpit has become more common after the 1990′s. Light-emitting diodes (LEDs) are more efficient than other systems and will be in all cockpits of the future. Blue lighting such as is are now common in US military aircraft requires much more lighting than white lighting.

Vitamin A is a vital element for night vision and adaptation. Vitamin A deficiency will make a significant difference in night vision.  However, excessive intake of Vitamin A will not give an apparent improvement.

Ample oxygen is necessary for adequate night vision more so than day vision. Above 4000 feet supplemental oxygen improves night vision. The most dangerous aspect of this is that the pilot has no way of knowing that he is not seeing as well.

Wearing of sunglasses during the day is one way to improve your night vision. Neutral gray glasses with UV resistant coating are best. At night, red lenses will absorb blue light and aid dark adaptation. Severely limit any use of bright white light at night since even a momentary flash can destroy night vision. Use blue, green or red LEDs for your evasion light.

Should blur interfere with the things you see at night, it may be indicative of night myopia. Squinting will help some or the use of glasses. If the eye is unable to focus on anything at a distance at night it may be having space myopia. Keeping the eyes moving can help limit these effects that are made worse by staring.

Objects are harder to see at night just because they are less well defined around the edges. This makes things appear farther away than they actually are. The requirement for corrective lenses (if you wear them) at night is much greater than during daylight.


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