What is it / how does it work? A laser rangefinder tells you how far away you are from an object. It can also measure additional parameters like speed of the object and horizontal or/and vertical angles, but its main designation is to measure distances. What is the maximum distance that my rangefinder can measure? Usually manufacturers announce the maximum distance measured to an ideal object (example: a mirror of a large size standing perpendicularly to rangefinder axis). In real life, these are the factors influencing performance. Ideal Conditions Interfering Conditions Overcast, Cloudy White, Shiny object Bright sunlight Snow, Rain Dark, Dull objects The rangefinder accuracy doesn't depend on outside factors and is determined only by the electronic circuitry. How does it know how far is the object? The laser pulses emitted towards an object bounce off back, and then they are collected by the device. After statistical evaluation, the unit knows the most probable time, which it takesfor the light to travel back and forth. This time, being multiplied by the speed of light, gives the precise distance.   Accuracy shown in meters or yards, it indicates how precise the measurement is. For example, ±1 m means that the result can be one meter less or one meter more against the real distance. Target quality indicator is based on how many laser pulses were returned and collected after bouncing off the object. The measurement is more reliable when the device receives more readings. If you measure in bad weather or through a cloggy landscape, the light can bounce off brushes, flakes, wires, posts, trees, etc. Some models can choose between the first (the nearest), the last (the farthest) and "auto" (the most probable) targets. The target quality indicator estimates the reliability of measurement as high, med or low depending on number of readings from the chosen target. Reticle seen through the eyepiece when looking at an object, it gives a point of reference to center over the image. It is usually a cross or a small square. Automatic scan mode means that without doing anything more than holding a button you will get continuous measuring from different objects, to which you aim the finder. Automatic rain mode will automatically distinguish between laser pulses bounced off raindrops or flakes, and off of the object you are intending to range. The fake reflections will be rejected. Automatic 100m mode will automatically distinguish between laser pulses bounced off close brushes or other foreground clogs, and off of the object you are intending to range. The fake reflections will be rejected.