Fujinon Polaris 7x 50 mm FMT-SX Binocular

Right: Fujinon 7x 50 mm FMT-SX Binocular (118,346 Bytes).
Click on image to see enlarged view (311,768 bytes)

The Fujinon company is based in Japan and is a well regarded maker of medical, photographic and sports optics products. Their FMT-SX series are their result of years of efforts to perfect a series of binoculars that are suitable for highly demanding marine and astronomical uses. These systems employ a refined doublet objective lens arrangement feeding substantial optical glass (BaK-4) porro prisms and so light fall off or vignetting are among the most modest in production binoculars. These are matched to a very comfortable five element eyepiece. Fujinon's multilayer electron beam deposited antireflection coatings assure a high degree of light throughput, and the elimination of ghost images or glare. The result provides an high degree of contrast, clarity and sharpness across the entire field of view; stars appear as pinpoints against a black velour background of the night sky. The clarity leaves little to be desired, and these feel reassuringly firm in the hand - complemented by their non slip coverings and rubber trim pads.

The balance of magnification and aperture provided by the 7x 50 mm FMT-SX can make good sense for some pursuing astronomy. Given the eye's inability to fully dark adapt in suburban areas, the large 7 mm diameter exit pupil provided by this binocular is more practical when used at darker sky sites than in the suburbs. But its convenience, and moderate cost with high performance make it a bargain for astronomers nonetheless. For those observing in suburban skies we most often recommend they consider the 10x 50 mm FMT-SX, or better yet the larger 16x 70 mm FMT-SX instead since with the extra magnification and light gathering provided by the 16x 70 mm FMT-SX (and it's predecessor the 14x 70 mm FMT-SX) a number of Company Seven's clients and some of our employees have been able to identify the entire Messier Catalog of deep sky wonders.

The eyepieces of the FMT series are constructed of five optical glass lens elements providing a field of view with little coma or distortion. All air to glass surfaces of the SX series are E-Beam coated. The eyepiece design provides flat field performance (hence the "F" prefix) with diminished field-curvature. When pointed onto the night sky the stars across most of the field of view are seen as intense pinpoints. And those stars seen toward the extreme periphery while not quite as sharp are clear and not distracting. The capability to image a star as an intense point of is the most difficult test of any optical system, and in fact in production "star tests" using artificial stars (usually a laser light source fed through a tiny perfect pinhole) are quite a common and valid technique for subjectively judging the degree of perfection of a system.

The FMT series display less pincushion distortion than most competing models. One has to work to see what little there is of it - but if you look carefully when panning then a slight bending of the image may appear towards the edges of the field of view. This level of correction comes with some balance of field of view, with a 52 degree apparent field of view, the Fujinon 7x 50 mm FMT-SX provides a field of view comparable or better than the best other Porro 50 mm models (which range 7. to 7.5 degree). In order to obtain wider actual fields of view, then one would have to consider our Carl Zeiss or Leica roof prism models which even in smaller apertures of 42 mm, these models may cost three times as much as the 7x 50 mm FMT-SX.

The color correction of the FMT-SX is quite good too, but then at only 7x this should not be obvious in most better binoculars. When looking at a bright star (Sirius, Vega, etc.) or a black bird on a tree contrasted against a light blue sky, you will not observe any obvious secondary color fringing. The terminator of the Moon for example is sharp, crisp, and three dimensional contrasted against the blackness of space.

The optical performance alone could be considered critical features for the demanding astronomer, and this is not commonly found with most other binoculars anywhere near this cost. But in addition to the very good optical aspects, there are highly attractive mechanical features:

• Individual Focus: the user initially sets focus by turning each of the two eyepiece housings clockwise or counterclockwise, and once focus is set for infinity then there is no need to fiddle with it. It is possible to adjust each independently and so if you have normal vision, then you may set "0" on the dial. Or if you have prescription glasses with one eye -1.5 and another +2 then it is a simple matter to dial these in on the eyepiece indicator scales and then make fine adjustments as may be needed. The depth of field of focus is so great with these binoculars, that once focused for infinity one may see details on objects as near as about eighty feet without having to focus again.
  

  Thus individual focus eyepieces and mechanical bridge design are helpful considerations for astronomy and shipboard marine use too where one needs to be able to pull the binocular up the eye and see a target in the distance quickly, and without wondering if an object coming out of the fog is in focus or not. The individual focus arrangement facilitates sealing against water and the elements.
  

  The eye relief (distance from the eyepiece lens to the eye) is 23 mm - unrivaled in this binocular aperture range. The eye relief is adequate for anyone who prefers to wear prescription or sunglasses. To provide that generous balance of eye relief and field of view means the eyepiece are about 50.8 mm (2 inches) in diameter and so those who have wide noses especially if combined with narrow interpupilary spacing may run into trouble. Those wearing glasses can simply roll down the provided eyecups. The rubber eyecups are slipped onto a threaded metal ring, and this assembly threads over the eyepiece; in time these can be replaced easily since they are threaded in place. Their 7 mm exit pupil make this binocular more practical to use for astronomy than those of similar aperture and with smaller exit pupils for those in the urban where their eyes may dilate to accept a large exiting light cone. This in suburban areas, and who can hand hold a 10x binocular could consider their cousin the 10x 50 mm FMT-SX.
  

  The "M" in the designation indicates this is a Fujinon binocular designed for marine use. The FMT-SX meet the US military specifications for water proofness. This rating is a measure of the binocular's capacity to survive immersion in water at depth for a period of time. Our sense is the binocular will tolerate more shock, vibration and water immersion than the owner will. Furthermore, the metal and alloy materials used in the construction are nonferrous and so the binocular will not distort a magnetic compass.
  

• The eyepiece focus and the 56 to 74 mm interpupilary (IP) spacing adjustment by pulling the hinged barrels together or apart. These motions are done smoothly with some mild effort, and stay where you leave them set. The seals and lubricants permit focus and IP spacing changes in temperatures ranging from from a low of -20 and + 50 degrees C.
  

  These eyepieces are wide enough that some people with larger noses and narrow IP spacing may not be accommodated. And this is in part why we at Company Seven continue to see the value of a showroom environment where one may visit and try a binocular first hand.
  

• Tripod Adapter: There is a good amount of area on these to grip comfortably, and to balance well in the hand. However, weighing 48.1 ounces, these binoculars are quite manageable by an adult of average height and good health. In all fairness, there simply is quite a lot of weight associated with the optical elements needed to provide such good images at this cost. Most amateur astronomers prefer to keep their binocular handy on a neck strap, at the ready to help sight a telescope onto a target or to observer wide expanses of sky however, some will not wish to hand hold a binocular when looking overhead for extended sessions. The solution for the weight issue is the optional Tripod Adapter used with a suitable tripod and head.

  The front of the 7x 50 mm FMT-SX binocular Central Axis Bridge incorporates a ¼ inch - 20 tpi threaded socket which will accept most L bracket style binocular Tripod Adapters; this socket is provided protected by a thread on plastic cover. This hardware option permits one to install the binocular onto typical camera tripod heads. While there are many cheap and simple adapters, and some poorly engineered adapters made, Company Seven recommends and stocks that adapter made by Fujinon for the FMT-SX series. Using this accessory one may leave their binocular fastened onto a suitable tripod and head, set up conveniently by a window for panoramic uses or for looking at a bird feeder, etc.

  Left: Fujinon 50 mm FMT-SX binocular bridge at Company Seven showing Tripod Adapter socket with protective cover removed (46,652 Bytes).
  Click on image to see enlarged view (118,957 bytes).

  However, most camera tripods do not work well for astronomical applications with binoculars and so for extended astronomical observing sessions Company Seven recommends an articulated parallelogram stand such as our Universal Astronomics UniMount™ Light Deluxe. Such a stand, when installed onto a suitable field tripod provides a most comfortable observing experience. Stands such as the UniMount™ do this by allowing the user to position a counter balanced binocular high enough to provide more comfortable head positioning; one could even be reclined in a lawn chair while observing objects overhead.
  

• Filters: The 7x 50 mm FMT-SX are among the few binoculars made that are able to accept optional filters. To support those who buy the Fujinon binoculars from Company Seven we offer:
  
  • Haze Filters: a nearly transparent appearing filter reduces the haze ("blue blur") or a bluish cast effects caused by UV light during the day especially when observing from high altitudes or from long distances, particularly over water. This filter can be used to protect the eyepieces in harsh climates.
    

  • Binocular Polarizing Filters: to cut the glare from water or snow, the shine from streets or leaves, windows, and enhance color saturation.
    

  • Binocular Nebula Filter (Light Pollution Rejection) Filters: darken the night sky background so that faint nebulae are more easily seen.
    

  • Solar Filters: permit the safe observation of Sun Spots.

• Cast alloy construction, sealed with the interior filled with dry nitrogen prohibits fogging or corrosion of the interior optics. Mechanical durability provides longevity. Given reasonable care, then these individual focus FMT-SX can provide a lifetime of good service that is simply no likely to be matched by similarly priced center focus 50 mm models.
  

• Baffled and antireflection covered interior construction prevents ghost images and reduces possible effects of glare all accomplished without any loss of contrast or definition. Observations of even the brightest objects (the Moon, etc.) against the background of the night sky show no ghosting or flare.
  

• Partial Rubber Covering: since July 2001 the FMT-SX binoculars are finished in satin black with a textured covering of the hand held areas. To protect the objectives ends and prism housings rubber coverings are provided. These keep the appearance of the binocular more intact since they prohibit chipping the anodized and painted areas from becoming chipped or scraped. The contribute some mechanical dampening too. Company Seven can service any Fujinon we sell, and we can replace the FMT-SX partial coverings over time if needed. Note, these coverings are not covered under the Fujinon warranty.

  It is possible to buy the FMT-SX fully clad in rubber armoring, but this adds nothing other than some convenience of handling when the binoculars are wet, or in extremely cold environments. And the objective lens covers are captive.

Below Right: Fujinon 7x 50mm FMT-SX from above, note the comparatively immense Eye Lens diameter (57,650 Bytes).
Click on image to see enlarged view (104,537 bytes)

7x 50 FMT-SX Binocular Specifications

† Twilight Factor (sometimes termed Relative Brightness) is a mathematical product of a formula. This formula however, does not factor differences of quality. For example two 7x 50 binoculars of vastly differing qualities will produce the same value by using this formula, and so this should only be used to compare binoculars of similar quality (i.e. a Fujinon 7x 50 FMT vs. Fujinon 10x 70 SMT-SX).

Twilight Factor = Square Root of (Diameter of Objective Lens x Magnification)

† Relative Brightness (or Relative Light Efficiency) pertains the the efficiency of the optical system in terms of throughput of light. This is measured by sensitive equipment and can help one to determine quality differences between models.

* Specifications are subject to change without notice.