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Source: National hunter’s magazine “Hunting” (source language - Russian)
Mostly compact devices all laser rangefinders of classic monocular design are not deprived of some of the drawbacks resulting from their compact size. Small magnification and field of view, low light transmission ratio (viewing channel is often used for displaying measurement results and for emitting laser signal) and light gathering power do not allow the rangefinder be regarded as an alternative to a simple binocular. 

In a certain moment some wise head produced an idea of combining a binocular with a rangefinder in one device. Lying just on the surface such solution helps to kill two birds with one stone by solving challenges of observation and measurement making the latter much more comfortable and by reducing the need of bearing an additional equipment thus reducing the weight – hybrid is still lighter and takes less space than two separate devices. 

But there is always a fly in the ointment. Majority of contemporary models of rangefinding binoculars are designed so that emitter and receiver together with the system of image displaying are integrated into the optic scheme of binoculars which results badly in color rendering and light transmission ratio of the whole system.

In the beginning of 2012 Yukon Advanced Optics Worldwide has produced a unique model of binocular with incorporated laser rangefinder – Expert LRF (Pulsar brand). According to the claim of manufacturer this model lacks all of the above drawbacks. 

The look of Expert LRF is more or less unconventional if not to say futuristic. Optic channels are arranged in one glass-fiber housing instead of two separate channels joined by a bridge. Mono housing design cannot be called know-how since existing on the market binoculars with image stabilization employ the similar scheme. In the places where hands grab the binocular it is covered with rugged rubber covers. 

Inter pupillary distance is altered by a reciprocal convergence or divergence of eyepiece blocks. The blocks move tightly which is good because the adjustment of IPD remains stable during the use. The eyepieces have tinted eyeshades which main function is to protect the observer’s eye from the lateral light exposure (if needed the eyeshades can be bended against the housing). 

The focusing is performed in a classic way with the help of central focusing unit while diopter adjustment is performed separately for left and for right eyepiece. The order of the adjustment is as follows: first adjust the right eyepiece to see the symbols of rangefinder clearly, and then with the help of central focusing unit the object’s image in the right eyepiece is adjusted after that adjust the image sharpness in the left eyepiece. 

The main peculiarity is that monoblock housing has enough space to allocate rangefinding unit. Emitter and receiver of rangefinder - two small objectives are placed between the viewing channels. In other words the rangefinder as a unit is separated from the binocular and its presence in the binocular’s design does not influence the optic parameters of Expert LRF as a unit. 

The only rangefinder’s part in the binocular is the image display in the right channel. It consists of a beam splitter that reflects the info projected by the LED matrix array. Patented block design allows to transmit all light gathered by the objective of binocular which is a great advantage over the LCD systems of image introduction. Two main problems characteristic for binoculars with incorporated rangefinder are solved – limited use in twilight time because of the low light transmission and visible bluish tint of image. In Expert LRF the image is bright and clear, observed picture is close to ideal and subjectively warmer in color. Operation in twilight conditions is perfect. Let’s take a close look at the rangefinder. It is very simple functionally without unnecessary extravagance. It allows to make unique measurements and conduct a continuous measurement in the scanning mode showing results in meters and yards. All controls (measurements, units switching, symbols’ brightness adjustment) are performed with the help of two buttons situated on the top of the housing. Rangefinder is powered by one 3V battery CR123A. 

Response time of rangefinder (showing the result from the moment of pressing the button) is half a second subjectively. Test measurements of distance to large objects (billboards on the highway) during good weather conditions have shown a repeating result (plus/minus 1 meter) at the distance of 925 meter. Distances measured to immobile vehicle up to 750 meters and distance to a walking man up to 567 meters. The measurements were made holding the unit in the hands elbows against the body (unfortunately Expert LRF does not have a socket for a tripod) but there were no problems with correct aiming – correct holding of the binocular plus unit’s weight resistance (0,9 kg) allow confidently place measuring cross on the target. 

Cross mark of rangefinder and results are displayed in red. There are five levels of symbols brightness switched by a button on top. In the twilight and low light conditions it makes sense to reduce the brightness of symbols, in the daytime when there is much light it is better to increase the brightness. 

Claimed range of operating temperatures is from -30⁰ up to +40⁰ C. There was no chance to check these figures, but absence of LCD screen in Expert LRF’s design allows to assume that the device is operative in temperatures below zero and in winter. 

A couple of short words about packaging and its contents. Binocular has a carrying case and a wide neck belt. However it is possible to use Expert LRF with a standard belt for binoculars and photo equipment. The battery and optic cloth are also included into the packaging. 

In general the binocular creates an impression of stability. The total weight is 950 g which is less than the weight of any binocular 8x40 and a rangefinder. The drawbacks include absence of tripod socket and the fact that it is impossible to put the unit on the table objectives down when the objective lids are open (in this case it is better to remove the lids totally). 

Both functional parts of binocular perform well: binocular gives a quality image, bright clear and realistic in color; rangefinder measures quickly and accurately, shows the data in the field of view correctly and ensures a good perception. If it is necessary to draw a line with a single word than we can say that Expert LRF comprises two fully functional devices in one body.