When in the patrol car, sometimes an officer needs to view outside of his box. Although commonly perceived as just a tool for surveillance, binoculars can help officers be witnesses to much more.

After questioning several law enforcement professionals, we found savvy officers who kept binoculars handy in their bags and used them regularly. One officer kept them slung around the passenger headrest. When pulling up to invisible-deployment-type calls, such as domestic violence or similar in-progress responses, he would scan a poorly lit block for activity, thus preventing parking too close to the call.

Another officer had a cadet riding in the passenger seat scan a mall parking lot while calling out license plate numbers as the officer entered them in a computer. A good pair of binoculars will also make a believer out of any officer who responds to a hazmat spill and discerns the numbers off a placard from a safe distance.

Focusing on features
Because of the variety of uses, law enforcement optics needs are unique and require several key product features. Brightness, field of view, stereoscopic viewing, glass characteristics and coatings are just a few qualities to consider.

Brightness is measured by the amount of light the optic allows through it. One factor of brightness is exit pupil. The exit pupil is the size of the disc of light the lenses deliver. The size of the objective (largest) lens divided by the binocular power calculates exit pupil. Thus, a 7x35 optic is 7 power with an objective lens of 35mm. The exit pupil is 35 divided by 7. One would say that this binocular has an exit pupil of 5 or 5mm.

The higher the exit pupil, the better. Although exit pupil is not as important as an optical instruments' coating, it is a good rule of thumb. Most adult pupils cannot dilate large enough to benefit from a disc of light bigger than 4mm. The larger exit pupil allows viewers a little leeway in eye relief - the distance from the ocular lens to the viewer's eye.

Although field of view would seem simple, it is hard to engineer. For example, as a binocular increases in power, field of view gets smaller. If the binoculars say 300 yards at 1,000 yards FOV (field of view), this means at 100 yards the glass can only take in 30 yards. Consequently, in the length of a football field, the user cannot see the entire end zone. For law enforcement binoculars, 325 yards or greater at 1,000 yards would be considered acceptable.

Stereoscopic viewing is the 3D effect desired when choosing binoculars. If this effect did not exist, everyone would just use telescopes. The higher the power, the flatter the image appears. This is the reason portrait photographers use telephotos - a higher power tends to make the background out of focus. Stereoscopic vision occurs when each eye can see more around a subject than the other and therefore the area of focus is different. This creates the 3D effect.

Different formulations of glass yield different characteristics in what they transmit. Picture a binocular lens as if it were a prism. The thinner sections of the lens allow light to pass through at a different rate than the thick sections. Uncorrected, a lens can produce streaky colors and ghost images. Additionally, poorly ground lenses can distort straight lines and turn circles into ovals. If these factors are compounded by poor alignment, or spurious light inside of binocular tubes, the results are disastrous. What the consumer pays for in a pair of binoculars are things they do not see. Unfortunately, it is hard to explain to the consumer why two binoculars with similar specifications have a $200 difference in price. These differences are subtle but invaluable to the officer who needs just a little more resolution and light gathering ability at the end of a shift when his eyes are tired.

No optical product ever manufactured will transmit 100 percent of the light that enters it. First, no glass is completely transparent. Second, each time light passes through a single lens, some is reflected back to the source. Third, it is impossible to grind lenses that are 100-percent symmetrical. It is engineering and lens coatings that make a binocular transmit light better.

One of the most important qualities in a binocular is the coating. A well-coated binocular will have reflective glass surfaces coated to increase their transmission efficiency. Coatings prevent the internal surfaces of glass from reflecting inside the optic. This is important as binoculars average about a dozen internal surfaces. Coatings are expensive and complicated to apply. Cheaper products simply coat the ocular (the lens closest to the eye) and objective (the largest) lenses. Most coatings are specific to the intended use of the instrument, such as hunting binoculars that have coatings designed to discern animals from foliage.

Most optics companies have proprietary formulas for their coatings. They can change the characteristics of a binocular so much that a poorly made product with huge objective lenses are obviously inferior to a pocket-sized, well-made optic.

The right optic for the right purchaser
As one can easily gather, law enforcement officers could benefit from all of these features. "Law Enforcement Technology" tested a total of six binoculars for patrol use from Steiner Binoculars, located in Moorestown, New Jersey, and Swift Optics of San Jose, California. Testers looked at two different styles: what the department would purchase and what an individual officer would purchase.

A department-purchased binocular would likely be used for deliberate deployments, meaning a product a supervisor would have in his vehicle. This tool will be used to make critical decisions in the field - the more accurate the information, the better the decision. These optics could be heavier and likely higher power, owing to the distance to the scene they will be used from. Close focus would not be as critical as a wide field of view. When deliberately deployed, they would more likely be found near sniper support locations or possibly used from a helicopter. Since several users might share the same unit, they should have variable interpupillary distance, as not everyone's faces are the same width.

The officer-purchased binoculars would be something an officer would carry in his duty bag. Durability is important, owing to the constant knocking around they will receive. They should have sturdy lens caps and rainguards (one-piece lens caps that attach to the straps) and compact cases. For some calls, they need to be small enough and light enough for cargo pockets. Both agency- and officer- purchased binoculars need to be waterproof and durable.

For the officer-purchased binoculars, close focus is foremost. For example, it is just as likely for an officer to need to view a VIN of a vehicle stuck in the mud only a few feet away, as it is for him to identify somebody on the other side of a city park.

General observations
Using the list of features that would benefit law enforcement officers the most, we tailored our tests for them. The areas we used to test the products varied from sea level to 7,500 feet and temperature extremes from freezing to 110 degrees Fahrenheit. The testing team performed some controlled environment tests like water resistance. We performed extensive side-by-side comparisons using optical test patterns. Finally, we put them in patrol cars and tried them on duty.

There are few standards for manufacturing optical products. For example, what one manufacturer might call waterproof, others might call water resistant. Both Steiner and Swift have similar standards for durability.

Many of Steiner's products meet military standards such as Mil-Std 810E for water and shock resistance and Mil-C-675C for optical coatings. Steiner uses Makrolon, a light polycarbonate that is rugged and stable. It also uses textured rubber, which has a similar feel, even in cold temperatures.

Swift covers their Ultra Lite models with dual-density rubber. Our testers found this material tacky, even when handled with sweaty hands. They used the same soft rubber on the focusing wheel. This rubber jacket gave them several advantages. They were vibration, shock and fatigue resistant. Combined with their luxurious twist up eyecups, all three models tested excelled in the long-term surveillance department.

Both Steiner and Swift interpreted the term "waterproof" the same way we did: they can handle a dunking, not just a sprinkle. Well-made waterproof binoculars should be nitrogen purged. This will prevent internal fogging. Imagine drawing a pair from a warm car to be used in chilly weather. They will eventually clear, but who has time to wait?

The Swift Ultra Lite 8x42 rivaled the Steiner 10x50 M&P in light gathering ability. While testing for contrast, users could pick individual lines and shades using optical test patterns. The difference in magnification between 10 power and 8 power is rather slight for what the products will be used for.

All models we tested could focus closely except the Steiner 8x30 and 10x50 models. If one adjusted the individual oculars, the closest one could focus was about 15 feet. For the 10x42 and 8x42 Swift models, focus was 6 feet to infinity. The 7x36 Eaglet focused 5.9 feet to infinity.

Following are more specific findings for each of the binocular models tested.

Steiner 8x30 Military/Marine
The Steiner 8x30 binocular is a popular individual purchase. When tracking vehicles in motion, users can concentrate their efforts on steadying the glass, not focusing.

The Sports-Autofocus system is unique to Steiner binoculars. Sports-Autofocus relies on the depth of field of Steiner products and begins with the user adjusting the individual oculars one at a time. The user picks a focus point 50 yards away and adjusts the oculars. If adjusted correctly, anything from 20 yards to infinity will be in focus.

Having superior depth of field has obvious advantages, especially after twilight. Because fewer receptors in the eye are usable due to impending darkness, it is harder to accurately focus any optic. Many purchase this style of binoculars for that reason.

Our testers did the same thing that most other Steiner users do: we carried the binoculars in the pocket and left the case in the car. No one, including our testing team, recommends this practice, but it happens. We recommend this model for officers known for dropping equipment while in foot pursuit.

Steiner binoculars in this configuration use Porro prisms made of BAK4 glass. Porro prisms give these binoculars their distinctive "M" shape because the ocular lenses are offset from the objective lenses. Whereas lesser quality prisms will "chop" the image creating a vignette effect on the edges, Steiner prisms are known for uncorrupted images.

Steiner 10x50 Police
Both the 10x50 Police and 8x30 Military/Marine models reflect the hard use philosophy of Steiner. They come with one-piece rainguards connected to the straps and objective lens caps that stay attached to the body when removed. There is a protractor for interpupillary distance. The lenses are recessed enough to protect them when dropped on an uneven surface, and they are firmly secured against shock in the body.

The Steiner 10x50 binoculars were light magnets. We were able to use them in subdued light while working crowd control during a fireworks display. While scanning crowds in intermittent light, officers were able to discern faces and license plates where unaided eyes could not even find vehicles and people. They were too bulky for officers to carry on a call, but are lighter than they look.

With most products, it is hard to accurately focus at night. However, the Steiner 10x50 M&P model was quick to put into action after dark. The field of view was only 300 feet at 1,000 yards, but this was offset by their excellent panning ability. One can move through an area like a panoramic picture.

Although both the Steiner 10x50 M&P and 8x30 models offer good clarity, the huge depth of field confused the user when looking through a chain-link fence, Venetian blind or screen window. With conventional focusing systems, the user can focus out the foreground. The images were consistent anywhere in the viewing field.

Swift 930 Ultra Lite 10x42 and 929 Ultra Lite 8x42
When given the choice between large objectives and fully coated optics, our experts would choose coated optics every time. When we brought out the Swift Ultra Lite 10x42, we were able to clearly read license plates at 100 meters lit only by a porch light. This was also a great demonstration of why officers should be selective about coatings. Spurious light did not confuse any of the Swift binoculars we tested.

Both the 8x42 and the 10x42 Ultra Lite models had similar physical dimensions. When we tested the 8x42 model using optical test patterns lit by a porch light, we were able to see some of the lines of crosshatching used for shading. This was like taking an eye exam and reading the copyright notice on the bottom of page. Both had the smooth focus necessary for surveillance use. Optically, both the 8x42 and 10x42 Swift models set the standard for true stereo vision. The 10x42 offered powerful magnification with a brilliant image and moderate field of view.

Both models felt more comfortable in the hand than the Steiner Police 10x50. Their twist-up eyecups were of softer material and more generous.

Steiner 8.5x26
At 11 ounces, this was the smallest and lightest pair of binoculars we tested. They also had the smallest objective lens and exit pupil. It has a dual-hinge design with Steiner's Fast Close Focus system. The dual-hinge style of binoculars is popular for inexpensive models because they fold up smaller than conventional styles. Unfortunately, it is a harder design to align than a single hinge one.

Steiner applied the type of coating that would be found on a much more expensive model, awarding them with fairly good contrast. This contrast compensates for the moderate light transmission inherent in the design. Most pocket-size binoculars are not much good in twilight. These were. They focused close enough for a very tall person to look straight down at the floor. However, the focus wasn't particularly fast. It took 3.5 turns to focus to infinity.

We anticipate that officers who always carry binoculars will want these. They are small, light and durable enough for a tactical vest.

Swift 825R Eaglet 7x36
Although we reviewed this product as a compact binocular, it could hold its own in either category. Because the Eaglet delivered unsurpassed performance, we recommend them for overall law enforcement use. First, they offer superior stereoscopic vision. Their edge-to-edge clarity and accurate color rendition gave our team hours of fatigue-free viewing. This is an example why magnification isn't everything. The Swift Eaglet 7x36 gave the best performance at twilight of any product we tested. Swift uses the Kellner method for optimizing an image. Two or more types of glass are used together, capitalizing on the qualities of both. The result is accurate color transmission without "ghosts" in the view.

The Swift Eaglet 7x36 was the only product that fulfilled each of the optics needs. With 374 feet field of view and weighing only 21 ounces, they were the lightweight choice. We were able to fit them into the utility pocket of an entry vest, a location they were well suited for.

The focus knob was easy to work, whether one-handed or wearing heavy gloves. The entire range of focus can be accessed in a single turn. The body flexed into interpupillary distance and held the setting. The Swift Eaglets felt and handled best of all models tested.

Like the other Swift models, their only major drawback was not performance related. The Eaglet 7x36 has individual lens covers. They are protective, but cumbersome. Swift should use a one-piece rainguard and flip-down objective covers that remain attached to the body. Considering the Swift Eaglet's reasonable price, purchasing after-market lens caps would not be a problem.