On June 6, 2017, two rather heavy boxes, sent by Nikon Europe B.V., Amsterdam, have arrived at my office. They include the new Nikon WX binoculars which I am going to test in the field during the next two weeks. There is much to do, and here I am going to report about my work in progress.
Upon opening the box, a strap emerges first which turns out to be the shoulder strap for the aluminum case. That case is 45cm long, thus suitable to serve as carry on luggage on airplanes, very rugged and well padded to protect the binocular. Its total weight, including content, reaches close to 6kg. Apart from the binocular, the case further contains the tripod adapter, a little handbook of no less than 240 pages (which offers an opportunity for the curious reader to learn virtually every language on this planet), lens covers and the neck strap.
I have covered most of the technical details of these binoculars in a previous memo, and further specs are available online, so that we may focus on practical issues here. The dimensions of these devices are considerable, in particular on the side of the eye: The eyepiece-barrels have diameters of 57mm and do almost touch at the closest inter-pupillary distance of 58mm. There is no way to get the nose in between them. The eyecups are, however, of conical shape and taper off near the eyes. They are covered with a rubber layer which supports a slip-free contact with the face, on which they firmly rest on the eyebrows and the nasal bridge, simultaneously. The eye-lenses of the oculars have diameters of 30mm (7x50) and 28mm (10x50), and their surfaces are concave.
The eyecups twist up and interlock safely at various distances. When fully down, about 2mm of the eye-relief is wasted (the 7x50 offers 17.7mm eye-relief, the 10x50 has 15.3mm). The interlocks are at elevations of 5mm, 8mm, 10mm, 11.5mm and 13mm (7x50), and 4.5mm, 7.5mm, 9mm, 10.5mm and 11.5mm (10x50). I found it most convenient to twist the eyecups up one stage to the first lock when observing without glasses, while Asian fellows with low-profile noses will have to arrest the eyecups at higher elevations (I have confirmed that with the kind assistance of my wife and son). With the 7x50, I am able to see over the entire, nicely wide field of view without the need to swivel the eye to the edges. The 10x50 has a wider field which my eyes cannot fully cover simultaneously. With glasses on and eyecups fully down, the 7x50 has shown me the entire field, while the 10x50 was losing the outermost 10% of the angle. These numbers may, of course, vary with each individual observer.
I have noticed that the 7x50 is designed with a rather low amount of pincushion distortion. Its true angle of view of 10.7 deg. thus translates into an apparent angle which closely follows the ISO Norm 14132-1:2001, yielding 66.6 deg. Its residual pincushion distortion is likely to increase that angle a little bit to a value slightly below 70 deg. The 10x50 has somewhat higher pincushion distortion and is exceeding an apparent angle of 80 deg. by quite a margin.
First observations during daytime confirm that both binoculars may well be used in handheld mode. Standing freely and unsupported, I have no problems using them over a few minutes to scan the landscape, without any excessive fatigue of the arms. Naturally, the 10x50 is the first one to lose performance when the muscles begin to tire. When the elbows are supported, set on a railing or on the knees while sitting on the ground, both binoculars are usable without time limits, thanks to their excellent balance. In all other situations, however, they are best mounted on a tripod with the adapter provided as a standard accessory. This is particularly true with the 10x50, which otherwise would not nearly allow to exhaust its considerable resolution.
To the upper left, the system of baffles is visible. The exit pupil (here shown the 7x50, similarly with the 10x50) appears well shielded and essentially free of reflexes (upper right). Even in serious back-light, the inner tube walls remain sufficiently dark (lower left). When the exit pupil is shifted to the edge of the eyepiece lens, then the amount of vignetting becomes visible. Despite of the wide angle of this binocular, less than 30% of the exit pupil is lost, which is excellent and promises bright images up to the edge of field.
I do not own any professional equipment which would allow taking good photos through the eyepiece. This photo is a most unsophisticated handheld shot taken with my 6 year old compact camera. To the upper left, the field stop is visible, including a blue colored fringe, well visible visually with the 7x50, but hardly discernible with the 10x50 binocular. A colored image of the field stop is an esthetic flaw in daytime observations, though irrelevant in the night. The picture to the right shows a section of the image in full resolution and indicates an excellent correction of chromatic aberration. Color fringes are, if visible at all, amazingly narrow and faint. The Nikon WX competes here with the very best binoculars, and this despite of its significantly wider field.
In difficult back-light situations, stray light may reduce the contrast of the image, but that happens rarely and should be noted only for the protocol. However, the large eyepiece lens is prone to catch reflexes when the light enters from the sides. Winged eyeguards may be useful here, though hardly necessary in the night. The overall stray light resistance of both binoculars appears - so far - excellent, further tests are going to be conducted. Today, when comparing the panning behavior of both binoculars, I found a well developed globe effect with the 7x50, which was absent with the 10x50. The latter binocular is panning more naturally due to its higher amount of pincushion distortion.
After sunset, the almost full moon was rising and we had the opportunity to verify the outstanding performance of both binoculars on our trabant. The contrast is excellent, no loss due to reflexes or ghost images is visible. Regardless whether the moon is placed at the center or edge of field - its image remains fully sharp to my eyes. If image curvature exists, then it is sufficiently small to be accommodated by my eyes without the need to re-focus the image. Close to the edges of field, a faint and very narrow color fringe turns visible. The level of correction of chromatic aberration amazes once again. With the 7x50, the shape of the moon turns somewhat ellipsoidal at the edge of field, which is a testimony of the low level of rectilinear distortion (or, equivalently, its higher level of angular distortion). Contrary to the 7x50 WX, the moon remains almost circular all over the field with the 10x50, due to its considerably higher pincushion distortion (or low level of angular distortion). Under the sky, I personally prefer the distortion pattern of the 10x50, which preserves the angular distances between stars in a cluster. In daytime observations, the absence of pincushion distortion produces those pleasant straight lines with the 7x50.
Transmission: I do not have official numbers about the visual transmission of these binoculars, but a comparison with a couple of other instruments, while inspecting a white sheet of paper through the upside-down binoculars, suggests a transmission of slightly below 90%. Though that would not be a record breaking number (top transmission values are nowadays reaching or surpassing 93% in high end binoculars), my estimate appears reasonable when considering the large amount of glass present in these WX binoculars. The image is of almost perfect neutral color, though I believe to discern a very faint yellow hue.
To my surprise, I was initially unable to find the roof edge, that thin line cutting through the center of field, when looking through the objective ends of common roof-prism binoculars. I had to let a flashlight shine through the eyepiece to make that faint line show up. This may indicate the high level of precision invested into the manufacturing of these prisms, and is supported by the observation that fairly bright street lanterns have not been able to generate any diffraction spikes which are otherwise visible with roof prism binoculars of lesser quality. They did, however, produce a couple of faint ghost images - pale reflections of the lantern - inside the eyepieces of the 10x50 binocular. These ghost images remained absent with the 7x50. Assuming that both binoculars obviously have identical anti-reflection coatings, the observed differences may be due to different curvatures of the lenses employed in these eyepieces. These reflexes are not worrisome in practical applications because the intensity of the street lights easily exceeded that of the full moon, and these ghost images should not deteriorate the contrast during astronomical observations.
The twilight test is passed without any issues. Here, the binoculars are, after sunset, pointed toward the direction of the illuminated sky, while observing details on motives in the foreground which are already in deep shadow. This is a tough test for the efficiency of the baffles, because light from the sky right above the object is shining into the barrels and more often than not causing a partial or total whiteout of the image, if stray light protection is inefficient. Moreover, it is more demanding than back-light tests for veiling glare during daytime, because in twilight, the observer's pupils are wide, and the chance of running into the light contamination of a side pupil is rather high. There is no issue with the Nikon WX: The image retains its full contrast, showing all details on the landscape despite of the glaring sky above the horizon.
Today, the evening sky cleared up for some time to enable a couple of observations of Jupiter, Vega, Arcturus and less luminant stars. The imaging of starlike objects is outstanding, and I only find minor issues close to the edges, in the outermost 10% of the angle. Here, both Jupiter and Vega showed some lateral chromatic aberration. The brightest stars do also display hints of a deformation, perhaps due to astigmatism. Stars fainter than mag 2, however, remained perfect all over the entire field of view, which is a spectacular result when considering its huge angle. No significant differences were visible between the 7x50 and the 10x50, the images of which seem equally well corrected. The view of star fields, or the Milky Way, in a truly dark night must be breathtaking through these binoculars. But I also noticed that the 10x50 is hard to focus precisely when used in handheld mode. Even though handheld usage is possible and enjoyable, the tripod should better be around for in-depth observations. Here, the 7x50 is significantly less demanding, and I would not hesitate to take it out into the fields while leaving the tripod at home.
The transparency of the atmosphere had suffered significantly after 11 pm, before it had turned fully dark, so that observations of deep sky objects or the Milky Way remained out of reach.
Last night I have been out again, with hardly improved seeing conditions, but this time until darkness. I supposed that star fields would appear perfect all over the angle of view with both Nikon WX binoculars, and - well - they almost do. Close to the edges there is a minor, rather, a very minor loss of sharpness, the stars are not quite as pinpoint any more as in the rest of the field. But I am splitting hairs now. These are the best views I have ever had under the night sky with any binocular. I have brought my trusty Meopta 10x50 Meostar, my most frequently used astro binocular, for comparison. That was a mistake, and my suggestion to anybody who wants to compare the WX to his favorite binocular would be: Don't do it! It just turns too ugly for any competitor I am aware of. The Meostar is a good binocular; it offers a 6.3° angle, with an outstanding center sharpness, and within 75%, stars are pinpoint. That makes 4.7° of perfect image. The 10x50 WX has 9° and is perfect within 90%, at least, which makes 8.1°, and the area of that perfect field is thus three times as large as with the Meostar. Even when compared to the best of the best, the Swarovski 10x50 EL WB, which has 6.6° and is close to perfection within 90%, the WX still offers almost twice an area of perfect star images. Similarly, the 7x50 has 10.7°, 9.6° (again 90%) showing pinpoint stars. The closest competitors, Nikon SP or Fujinon FMT-SX, have 7.3° and 7.5°, and pinpoint stars within 85% (Nikon) and 80% (Fujinon), thus 6.2° or 6°. The Nikon 7x50 WX has about 2.5x as much area of perfect imaging as its competitors. At least one benefit stuck to the Meostar in this night: It suddenly felt as light as a feather, and I shall never again complain about its weight exceeding barely 1kg!
Last modified: June 2017