1. Introduction to Laser Rangefinders Laser RangeFinder Basics Before we had laser rangefinders, we had much inferior optical rangefinders whose accuracy varied with the distance and which often gave inconsistent readings from one user to the next. They were also large and cumbersome for field work and rather slow to operate. Because of these shortcomings, most folks tended to go without a rangefinder when they headed to the hunting field or golf course. Laser rangefinders have changed all that. Even the lowest priced laser rangefinder is capable of far better performance and accuracy than any optical rangefinder and all in a unit that can fit in your pocket in many cases. So how do they do it? What makes laser rangefinders work? What are the basics of a laser rangefinder? Despite all the technology that goes into a laser rangefinder, they are rather simple in concept. They are, in fact, very much related to auto focus cameras which used the same technology prior to the widespread use of laser rangefinders.

2. Laser Rangefinders - Just Like Autofocus Cameras How Laser RangeFinders Work In autofocus cameras, an invisible infrared laser beam is projected to the subject. The beam hits the subject, reflects back to the camera and is detected via a sensor in the camera. A computer chip then translates the time it took for the beam to travel to the subject and back into a distance to the subject. Based on this calculated distance, the computer chip then sends a signal to motors on the camera/ lens with instructions to focus the lens to that specific distance. Initially, this technology was slow and clumsy and not altogether reliable, but as with all things digital, the technology moved forward, rapidly. In a few short years, manual focus cameras were all but obsolete.

2. Laser Rangefinders - Just Like Autofocus Cameras How Laser RangeFinders Work Laser rangefinders use that same principle, minus the camera lenses and motors. Once again, an invisible infrared laser beam from the laser rangefinder(LRF) hits the target, then reflects back to the rangefinder. A computer chip in the LRF then translates the time it took for the laser beam to return into a distance and that is then displayed on a screen. It's lightning quick because a laser beam moves at the speed of light. Unless otherwise specified, you can expect just about any LRF to have an accuracy of plus or minus one yard/meter. When more accuracy is needed, technology now allows the most sophisticated LRFs to measure down to mere inches.

3. Not All Laser Rangefinders are Equal The Power and Range of RangeFinders As you might expect, then, not all laser rangefinders are equal. Your first glance at the various models will reveal that some laser rangefinders offer greater range than others: some 400 yard range, others 800 yards and some are accurate to distances greater than a kilometre. So are the long range models using more powerful lasers? No. In fact, typical consumer handheld laser rangefinders all use a class 1 laser. So why do some laser rangefinders list a 300 yard maximum range and others a 1200 yard maximum range? The difference is not in power, but in quality. How tight, how uniform and the capability of the computer chip or sensor to process the information determine the distance. A sensor that can detect lower light, filter out false information and so on will handle greater ranges.

4. Determining Maximum Range and Tilt One of the most important variables for determining maximum range is the user. Imagine that you are a hunter and you are trying to get the range on a deer that is somewhere in the several hundreds of yards distance category. At a distance of 300 yards, that deer presents a tiny target. You put the LRF crosshairs on the deer and try to hold it steady enough to get a reliable reading. The LRF will likely be no easier to steady than the crosshairs on your riflescope. In fact, because the LRF is much smaller and lighter than your riflescope/gun combo, it can prove much harder to steady. So even if you have the most capable 1500 yard laser rangefinder on the market, if you can't hold it steady enough to get a reading, it's no better than a cheap laser rangefinder. Experienced hunters often try to target a large object close to a distant game animal rather than the animal itself when steadiness is an issue. This is a laser rangefinder fundamental that is overlooked.

5. Angle Compensation If all we ever encountered was flat, level ground, we'd have no need for this advanced laser rangefinder feature. Once you or your target are on different levels you need to factor in the elevation difference as realize that you are now dealing with two distance measurements. To illustrate this, let's assume you are standing on a hill that is 100 feet in elevation. Below you, at the bottom of the hill is a large tree that just happens to be 100 feet tall. The tip of the tree, then, is at eye level from your position on the top of the hill. The base of the tree, though, is far below you, down at the bottom of the hill. How far is it to the tree?

5. Angle Compensation That's an incomplete question. You have to decide which part of the tree you want to target. Will it be the tip of the tree straight out in front of you at eye level or will it be the base of the tree that is far below you at an angle? You decide to take both readings. You quickly discover that the distance to the tip of the tree at your eye level, the horizontal distance, is considerably shorter than the straight line distance down the hill to the base of the tree. That distance corresponds to the hypotenuse of the triangle that you are making with the tip of the tree and the base of the tree. It's simple geometry, but it's a lot easier to find if you have the right laser rangefinder.

5. Angle Compensation If you have a tilt or angle compensated rangefinder, though, it will compensate for the difference in elevation because it can 1) detect and measure the angle produced by the difference in elevation and 2) calculate the horizontal distance based on that angle and 3) do it in the blink of an eye. Some models may also display the angle involved, but all models will display that corrected or horizontal distance to the target for you.

6. Laser Rangefinder Modes Scan Mode Scan mode is a useful mode found on most laser rangefinders. It's a useful feature to get the lay of the land and it can also be used to note distance changes on a moving target. Brush, Zip mode, Distant Target Priority This is actually a filter that tells the LRF to ignore intervening brush between you and your target. In other words, the LRF seeks to target the more distant objects that you want to see. If you are an experienced hunter or target shooter, you know that your bullet begins to drop as soon as it leaves the muzzle. Just how much of a drop occurs at any given range will depend on your cartridge, your load used and how you zero your gun. LRFs with a ballistic program will help you determine how much hold over or hold under to use for a given distance with your cartridge.

7. Magnification Most, but not all, laser rangefinders offer some magnification to improve target accuracy. This effectively increases the range at which you can use your LRF. Compact laser rangefinders are usually a monocular, though there are binocular laser rangefinders on the market. Binocular laser rangefinders offer you the convenience of two instruments in one, but they are more expensive than monocular laser rangefinders and they are also heavier and bulkier than the same binocular without the laser rangefinder. An important basic principle of laser rangefinders to remember is that they use a beam of light to get readings off a target that can be affected environmental factors as well as the reflectivity of the target. If something is blocking your view of a target, you'll likely struggle to range it.

8. Fog, Rain, Dust, Humidity, Temperature, Elevation Any environmental factor that slows down that beam of light or disperses that beam of light from your LRF can effect the performance of your LRF. The speed of light is constant in a vacuum, but it varies when passing through different types of matter. For instance, the speed of light is different through denser air than thinner air, so things such as elevation, humidity and even temperature, which affect air density, can also affect the accuracy of an LRF. In general these factors are only of small concern and can all but ignored for field work, but they're important to keep in mind.

8. Fog, Rain, Dust, Humidity, Temperature, Elevation Fog, rain, dust and smog, on the other hand, have a more dramatic effect on rangefinders. Because of this, some LRFs have a rain mode or fog mode which help to an extent, but keep in mind they can't work miracles. Heavy rain, snow or fog can render an LRF nearly useless by drastically dispersing that beam of light. Another rangefinder fundamental to be aware of is waterproofing. This is highly recommended for outdoor use, especially if you expect to encounter inclement weather. Waterproofing seals not only keep out water, but also dust and dirt.

9. Target Reflectivity How Color and Surface Brightness Affect Reflectivity A hard, smooth, shiny, bright colored target reflects a beam of light to your LRF much better than a rough, dark, opaque target. That's why the effective range of an LRF is better for the first type of target and much reduced for the second. Color can have an effect. Dark objects and dark colors tend to absorb light energy from that LRF beam and reflect back less light to the laser rangefinder. Range is reduced for these types of targets. Likewise, targets with rough textures or soft textures tend to disperse light and therefore reduce the amount of light reflected back to your LRF. This is why some manufacturers list a reflective range and a non-reflective range for some models of their laser rangefinders.

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