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Hendon Publishing

Taking Aim at the Dark

Low-light training and the right equipment is essential to officer survival. The 1995 to 1999 study “California Peace Officers Killed and Assaulted in the Line of Duty,” published by the California Commission on Peace Officer Standards and Training (POST) in November 2001 found that most officer-involved shootings occur within the first two minutes of the officer arriving on scene with no time for adaption to low light. 

The study also found that 70 percent of the shootings occurred during the hours of darkness. Lighting was a contributing factor, according to 39 percent of the officers. These statistics are similar to the national statistics compiled by the FBI. The importance of low-light shooting skills isn’t diminished during daylight hours. Even during the day, there will be many situations in which you are faced with reduced or inconsistent light.

Self-illuminating night sights have been available for over 40 years. The first U.S. Patent for “Radioluminescent Gunsight and Method” was issued in 1972 to Julio Santiago and Eliott Knudsen. Today, tritium night sights are included as an option on many models of handguns as they come from the factory.

Tritium sights are available from AmeriGlo®, Meprolight®, Trijicon®, TRUGLO® and XS®Sight Systems. The MAKO Group is the exclusive U.S. importer and distributor for Meprolight Self Illuminated Sights to the law enforcement and civilian markets. XS Sight Systems 24/7 tritium sights utilize Trijicon vials.


Passive Aiming Devices

Tritium sights differ from lasers and flashlights or tactical lights in that they are passive aiming devices. They don’t illuminate either the target or the shooter. They are entirely self-contained and don’t require any external power or exposure to an external light source. They are dependable and insensitive to temperature variations.

All tritium sights work in the same manner. Tritium sights contain special radioluminescent inserts. The inserts consist of small glass capsules filled with tritium. 

Tritium is an isotope of hydrogen that contains an extra atom. The inner walls of the capsules are coated with a phosphor compound. As the tritium decays, beta rays (electrons) are produced. The beta rays strike the phosphor particles on the inside of the glass, exciting the phosphor particles and causing them to emit visible light.

The color of the light emitted is determined by the type of phosphor that is used. Green, yellow and orange light emitting capsules are available. Green appears to be the brightest color to the human eye. This is why night vision goggles and scopes employ of green phosphor. Yellow and orange aren’t as bright, with orange being the dimmest of the available colors. Although other colors could be provided, they would be too dim to the eye to be practical for use in night sights.

XS Sight Systems Express XS 24/7 Express Big Dot Tritium and Express XS 24/7 Standard Dot Tritium sights are designed to further enhance acquisition in high-stress defensive situations under all light conditions. To align the sights, you simply center the Dot front sight over the shallow V and vertical bar of the rear sight. XS 24/7 sights are available for pistols, rifles and shotguns.

XS Sight Systems has recently come out with its XTI™ (Xpress Threat Interdiction™) angle mount sights for the AR platform. Designed in conjunction with Lone Star Armory, the XTI BUIS feature the XS Express Standard Dot Tritium front and White Stripe Shallow “V” rear for quick acquisition in CQB situations



Tritium sights need to distinguished from photoluminescent sights. Photoluminescent sights differ from radioluminescent sights in that they require activation by either sunlight or an artificial light source. Think of them like a rechargeable battery.

Super-LumiNova®, a strontium aluminate oxide pigment, is the brightest photoluminescent pigment. While Super-LumiNova is often quite bright immediately after exposure to light and doesn’t suffer any practical aging, the luminescence diminishes rapidly and is gone within a few hours after exposure. If the pigment is activated by artificial light, luminescent output is often 1/10 of when it is activated by sunlight. 

Trijicon HD™ Night Sights feature a hybrid design that incorporates a yellow or orange Super-LumiNova paint outline and tail blade on the front sight in addition to the tritium to increase visibility and hasten acquisition.


Fiber Optics

Night sights also need to be distinguished from fiber optic sights. Fiber optic sights are designed to create contrast between your target and sight with bright color. For this reason, they are popular with many hunters. Fiber optic sights rely upon ambient light. While the light gathering capabilities of the fiber optics can brighten the sights in daylight and as dusk or dawn and in so doing hasten target acquisition, fiber optic sights should be considered daylight sights, unless there is supplemental illumination of the sight.

TRUGLO has come out with a hybrid tritium/fiber optic (TFO™) sight that is a patented combination of tritium and fiber optic technologies. The TFO handgun sight utilizes the same technology that was first employed in the company’s TFO archery pins, which were designed for bow hunters. The tritium maintains the brightness of the sight in low-light or no-light situations.


3-Dot and Bar-Dot Systems

Tritium sights are available in a variety of fixed-sight and adjustable-sight models. Both three-dot systems and bar-dot systems are available. The front sight insert on all night sights is green because this color is the easiest for the human eye to see in low light. It also provides the greatest contrast from muzzle flash and is the longest lasting of the colored tritium.

Although green three-dot systems are the most common, many shooters prefer two-color night sights with green front and yellow rear dots. The use of two colors provides more distinction between the front and rear sights and helps avoid the possibility of momentary confusion as to which dot is which. Also, many shooters find that two-color night sights make it easier for them to concentrate on front sight in low-light conditions, aiding accuracy.


Service Life

Everything else being equal, all tritium sights have the same life irrespective of the manufacturer. Tritium has a half-life (the time required for half of the tritium to decay) of 12.26 years. As the tritium decays over time, the brightness of the capsules will diminish. At the half-life, the sights will have lost approximately 50 percent of their illumination. From a practical standpoint, night sights may remain serviceable for up to 15 years.

This is not to say that there aren’t differences between the various tritium sights on the market. There are definite differences in construction, ruggedness, brightness and warranty. Tritium sights don’t pose any health hazards whatsoever. The amount of radiation that’s emitted is minuscule. It’s classified by the NRC as “below regulatory concern.” The exposure is approximately one-thousandth of that which one would receive from a watch. This minute exposure is obviously certainly nothing to worry about.

Even if the capsules were to rupture, there wouldn’t be any hazard. The beta radiation emitted by Tritium is unable to penetrate the human skin. Even a thin sheet of paper completely blocks it. A typical three-dot tritium night sight contains approximately 50 millicuries (mCi) of tritium. According to documentation on file at the NRC, it would require the simultaneous rupture of 10,000 tritium sight capsules in a small room to potentially pose a radiation health risk.


Increased Hit Probability

Due to their advantages, tritium sights are rapidly becoming considered to be essential equipment for law enforcement firearms. Nevertheless, the fact remains that most law enforcement firearms today aren’t equipped with night sights. The primary reason undoubtedly is their cost. Night sights do add to the cost of the weapon. This leads to an important question. Just how much of a tactical necessity are tritium sights?

To accurately aim a weapon, you need to be able to clearly see the sights, something that is often difficult or impossible to do with standard sights in low-light situations. Tritium sights have proven to be a valuable aid in delivering precise and accurate fire in low-light conditions. Tests that were conducted at the FBI Academy demonstrated an increase in night-firing accuracy of as much as 500 percent when tritium sights were used. 

Do tritium sights improve hit ratios on the street? The answers are not clear-cut. Most officers involved in spontaneous shooting scenarios report either not using their sights or not remembering if they did. There could be several reasons for this. When faced with a threat, the human mind instinctively focuses on the threat. Also, the physiological effects of extreme stress can make it difficult, if not impossible, for the eyes to get a clear sight picture.

This isn’t to say that tritium sights aren’t advantageous to have in close range, spontaneous shooting scenarios. Tritium sights allow you to use a flash sight picture in situations where this would otherwise be impossible due to low ambient lighting. The flash sight technique, also known as the front sight method, is, according to proponents, easier to learn than point shooting and inherently more accurate. With practice, there is very little loss of speed by using this technique. 

At longer distances, or in situations where there is time to use the sights, tritium sights really come into their own. Tritium sights really shine in non-spontaneous shooting scenarios where the target is clearly identifiable and standard sights couldn’t be seen or wouldn’t be silhouetted against the target. They are invaluable in these scenarios.


Eugene Nielsen provides investigative and tactical consulting services and is a former officer. He may be reached at

Published in Law and Order, Mar 2014

Rating : Not Yet Rated

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