How Does a Laser Rangefinder Work?

You’ve seen the magical wonders that a rangefinder can perform, telling you in a matter of seconds how far away that deer is. Or maybe you haven’t seen it in action, but you’ve heard about it and are considering picking one up for yourself.

Whether you’re in the market for a new rangefinder or just want to know how to use your existing device more effectively, it’s important to have an idea of the fundamentals of laser rangefinders. This article will explain how rangefinders work, and how you can make the most of your purchase.

The history of the rangefinder

Before laser rangefinders came on the scene, we had to rely on much inferior optical rangefinders. These devices had widely variable accuracy based on distance, and they often gave inconsistent readings from one user to the next. They were also monstrously large and cumbersom for field work, and took forever to operate. In terms of accuracy, they were only slightly better than a guess. Because of the shortcomings, most people went without a rangefinder when hunting or golfing.

Enter the laser rangefinder

The advent of the laser rangefinder changed all of that. The most economical laser rangefinder is far better performing and more accurate than any optical rangefinder, and can usually fit in your pocket. How do they do that? In truth, a laser rangefinder follows a pretty simple concept very much similar to that used in autofocus cameras.

The autofocus camera

Within an autofocus camera there is a laser emitter. The invisible laser beam is projected to the subject, reflects back to the camera, and is detected by a sensor. A computer chip then calculates the amount of time it took for the beam to return to the camera, and then it gives instructions to the motors on the camera or lens on how to focus to that particular distance.

Just like that

Laser rangefinders follow that same principle, but don’t have the camera lenses and motors. Instead, the computer chip translates the time it took for the laser beam to come back from the target into a distance that is displayed on the screen. The laser beam moves at the speed of light, so you get your reading in a matter of seconds. This technology is insanely accurate, so you can usually expect a laser rangefinder to have an accuracy of +/1 one yard, unless the manufacturer specifies otherwise.

Not every rangefinder is the same

With such a simple concept, you would think that all laser rangefinders would be the same, but they’re not. Looking at various models, you’ll see that some offer a far greater range than others. You’ve got your 400-yard rangefinder, your 800-yard rangefinder, and even some models that are accurate out to more than a kilometer. Do these longer range laser rangefinders have more powerful lasers?

Actually, no, because typical consumer laser rangefinders all use the same class 1 laser. The reason for the difference in range is not power, but quality. Some rangefinders have a more tight and uniform laser emitter, and some have better computer chips or sensors to process the information and determine the distance.

Remember this: the maximum range for a laser rangefinder should be taken with a grain of salt. There are a huge number of variables at play here, from weather conditions to the size of the target to the steadiness of the user’s hands and more. Because of this, many manufacturers have stopped listing a maximum range at all.

You are the most important factor

In figuring out how far your rangefinder will accurately work, you are actually the most important factor. Well, actually, it’s the steadiness of your hands. Imagine you’re trying to get a range on a deer that’s several hundred yards away. It makes for a tiny target, and you’re trying to put the crosshairs on the animal and hold it steady enough for a reliable reading. This can be incredibly difficult to do, and the laser rangefinder will probably be more difficult to steady than the crosshairs on your riflescope, because the device is much smaller and lighter than your riflescope/gun combination. Quite often, experienced hunters will try to target a large object close to that deer in the distance instead of the animal itself. The moral of the story is that using the rangefinder correctly is just as important as having a high quality model.

Things in the way

The other factor that can impede the accuracy of your readings is the presence of scrub or brush between you and your target. The laser beam reflects off the first object that’s reflective enough to send it back, and sometimes that can be a bush or some brush between you and your target. The beam is wide enough that some of it goes through the brush and is reflected back to your laser rangefinder, but the brush can still be what the device gives a reading on.

That’s why many laser rangefinders have a brush mode, zip mode, or distant target priority mode. This is basically a filter that tells the laser rangefinder to ignore brush between you and your subject, looking to target the most distant objects instead. For hunting laser rangefinders, this is a must-have feature and is usually the default mode.

Keep an eye on the weather

Environmental factors can often slow down that laser beam, or disperse it, affecting the performance of your rangefinder. The speed of light is constant in a vacuum, but we don’t live in one. Denser air produces a different speed of light than thinner air, so your elevation, humidity, and even the ambient temperature can affect the accuracy of your laser rangefinder. These factors are usually just a small concern and can be mostly ignored, but wait…there’s more.

Fog, rain, dust, and smog can have an even more dramatic effect on your laser rangefinder. Heavy rain, snow, or fog can render your laser rangefinder all but useless by dramatically dispersing the laser beam so that the readings are way off. Keep that in mind when you’re hunting in inclement weather.

How reflective is your target?

I read a lot of customer reviews when I’m evaluating a rangefinder, and one of the most common complaints I see is about the ability of the rangefinder to get a reading on a deer. “Advertiser XYZ says this thing is accurate to 1,000 yards, but I couldn’t even get a reading on a deer from 500 yards!” What most of these consumer reviewers fail to take into consideration is target reflectivity.

A hard, smooth, shiny, bright-colored target reflects a beam of light back to your laser rangefinder much better than something that is rough, dark, and opaque. Dark objects and dark colors tend to absorb the light energy rather than reflecting it back, too. Next, a target with a rough or soft texture will disperse the light, reducing the amount of the laser beam that gets reflected back to your rangefinder.

In other words, the broad side of a white house is going to reflect the laser beam much better than the flank of a fur-covered deer. This is why smart manufacturers list the reflective range and non-reflective range for their laser rangefinders. Hunters should keep in mind that a game animal is always considered a non-reflective target, and will have a shorter range than a golf flag, for example.

Summary

There ya go, a brief outline of how laser rangefinders work, as well as some tips on how to make the most of your purchase. Now that you’ve educated yourself, be sure to check out our laser rangefinder reviews before you go make your purchase. You might even find a good deal or two!