Nikon WX 10x50 IF Evaluation

20 17 Nikon's centenary, many people will wonder how Nikon will celebrate this centenary birthday. In particular, the photography circle is still looking forward to what new products Nikon can launch. In fact, Nikon has not done so. On the contrary, in order to inherit the tradition (in fact, Nikon is closer to sports optics than photography), Nikon released two telescopes of Super Bull X, saying that Super Bull X is not an exaggeration, because these two mirrors show Nikon's powerful strength. Regardless of cost and size, God knows what Nikon can do.

And the result? Nikon brought two telescopes, WX 7x50 and WX 10x50. From the parameter point of view, the most common thing between the two images is the name. In terms of visual field, the two models are 10.7 degrees and 9 degrees respectively, which is also the most suitable place for these two mirrors. In order to compare the visual field of these two models, you need to know that the widest 7x50 and 10x50 are only 7.5 degrees and 6.5 degrees. In addition, Nikon also guarantees that in such a huge field of vision, the edge should be well corrected and the distance from the pupil should be comfortable enough.

So what are the disadvantages of these two models? As I have already said, volume/weight/cost, the final mass-produced products of these two mirrors weigh 2.5 kilograms and are 30 centimeters long, and the price is higher, reaching 4W. If you choose the centenary edition, it will be more expensive.

design

It must be cool to evaluate such a mirror, but I think it is necessary to introduce the optical design of this mirror.

The objective lenses of modern telescopes are basically universal, and the slightly better ones may be separated by two pieces of ED (low dispersion glass) bands. Nikon's design goes further, using three pieces, one of which is ED glass.

From the above picture, you can basically see the lens layout of Nikon WX. If you look closely, you may think that there are only two objective lenses. In fact, the first piece may be laminated, and then you can see Abbe prism, which is a total reflection prism. This configuration can ensure the brightness and contrast of the picture.

You can see that there are two flat-field mirrors behind the prism, which are mainly responsible for compensating the curvature of the field of view from the center to the edge of the picture. Behind it is a huge eyepiece group, which looks like about 6 pieces, with 2- 1- 1-2 layout. The manufacturer claims that there are three ED lenses in the lens barrel, so there may be ED lenses in addition to the objective lens, eyepiece lens and field lens.

But what I said is only a personal guess, because from the side, Nikon did not say whether it was 7x50 or 10x50. So can you think that the two telescopes use the same objective lens and prism, followed by a flat-field mirror and a more complicated eyepiece?

Since it is born for performance and uncompromising, the coating of the objective lens is also top-notch. Nikon claims that all air surfaces are coated with the best multilayer coatings, and prisms are also coated with phase films.

Can such a complicated optical structure guarantee the light transmittance if it is used to observe stars? Obviously, this mirror has so many air surfaces, about 20? Even the best coating will lose 0.2%-0.3% (visible light) per piece of direct light. Let's assume a loss of 0.25%, then 20 is 5%. However, the reduction of coating efficiency should also be considered, especially far away from the visible spectrum, because the reflector will be optimized for the visible light band, and there are some large-angle incident light, and some angles of the ultra-wide-angle eyepiece are particularly large. Considering these, it is not surprising that the loss is 10%.

That's not all. If it is a simple small mirror, we can just say that the coating is ok, and we can ignore the problem of light absorption. This is also reasonable, because modern mirrors are optically clean and the optical path is as short as a small mirror, so the problem of light absorption is secondary to coating. However, because Nikon WX has such a long optical path and so much glass, this aspect still needs to be considered.

We don't know what kind of glass Nikon uses, but we can imagine that Nikon must use the best glass, just like some top mirrors use short HT glass. The 400 nm Schott glass will absorb 0.2% at the optical path of one centimeter. The bigger problem lies in the prism, because if you use Bak4, even if you use Short HT, you will lose 0.7%. Of course, SK glass can also be used, and the absorption rate drops to 0.4%.

We can roughly guess the optical path of WX through the cross section, and we can get that the optical path length of WX is 13 cm by pixel marking method, and half of it is in the prism. In general, you have to add 6-7% blue light loss, and the light loss in the middle and red parts of the visible spectrum is much smaller.

The mirror is magnesium alloy, the hand-held part is covered with a layer of leather, the eyepiece has six gears, and the end of the eye mask is rubber. In addition to these, the mirror body was also washed with nitrogen, and the waterproof depth reached 5 meters (10 minute).

The buyer can get a beautiful aluminum alloy box, a leather objective/eyepiece cover, a tripod adapter and two belts (one for the mirror and the other for the box). The mirror itself comes with a 10 year warranty.

Measure with an instrument

Measuring aperture of objective lens: left -50mm, right -50mm.

Actual multiple: 9.97 times

Light transmittance: 85%

Color difference: excellent center and moderate edge.

Divergence: negligible, starting point of needle tip

Distortion: The line with a radius of 38% from the field of view has radian.

Huicha: Actually, it's invisible. Even at the most extreme edge, there are dots on the tip of the needle.

The edge of the field of vision is blurred: very clear, all the way to the extreme edge.

The edge of the field of vision is dark: no.

Screen whiteness: slightly yellow-green, refer to the transmittance chart.

Optical axis: perfect

Internal reflection:

Mirror body and mirror cavity: very large and heavy, made of metal, probably the largest 10x50 specification on the market. The appearance is covered with leather and feels good. Watch out for 6th gear, it's rubber. Because the field of vision is too large, you need to pull the blindfold back or just pull it in one gear to see the full field of vision. Made in Japan

Focus: Independent focus, huge eyepiece. There are two texture rings on the eyepiece for focusing, which can rotate smoothly and have acceptable damping. The diopter adjustment is 5, but the reality is far more than that. Some look strong and cattle.

Shelf: It has a central shaft and can be connected to a shelf adapter.

Pupillary distance adjustment: 57mm-79mm

Recent focus: 8.2 meters

Apparent visual field: the apparent visual field is simply converted into 89. 1 degree (simple conversion), and the tangent formula is converted into 75.9 degrees.

True field of vision: measured 8.94 degrees, slightly smaller than the official claim, which is very awesome in this specification.

Internal extinction: it is very dark, and there is no grating inside, but there is a partition between it and the prism. There is also black around the prism, but there are gray particles on the prism.

Vignetting (trimming):

Prism: high quality Bak4 prism.

Antireflection film: the objective lens is yellow-green, the prism is blue, and the eyepiece is yellow-green-blue. Low intensity shooting

Warranty: 10 year

Score: 84.6%

superiority

disadvantaged

abstract

I used too much space to introduce the theoretical transmittance and optical loss, and then I will talk about some actual data. The following is Nikon's transmittance chart.

According to the above picture, we can confirm that our judgment is correct. The transmittance is as high as 90%, which is the red part, and this spectral absorption can be ignored. These light losses are mainly caused by the air surface of glass. The middle part of visible light is about 85%, and the blue part is less than 80%. The remaining light loss is the big prism of Nikon WX. Because light absorption is selective blue, the color of this mirror is not perfect. The colors are green and yellow. Of course, this can't blame Nikon. At present, the glass layer is just like this, and the complicated light path will inevitably have more light loss.

I mentioned some shortcomings found after the test, so I'll add two more. Despite Nikon's guarantee, I still don't believe that such a wide eyepiece can perfectly correct the distortion. According to the actual measurement, we are right, or at least, Nikon didn't do better. The result is not necessarily bad, it belongs to the medium level, but obvious distortion can be seen on the picture.

The second problem is the huge vision. I'm not sure if Nikon can do better or in other ways. Nikon claims that the eye mask has six slots, but in fact, if you want to see the full field of view, you can only choose not to pull the eye mask or just pull one slot, and the other four slots can be said to be useless. In addition, if you want to look good, you have to cover your eyes with your hands, because it is difficult to avoid side light in such a large field of vision, which may affect your observation mood.

Of course, such a great mirror really doesn't have so much to criticize. Just like distortion, I don't believe that the sharpness of the visual field edge can be corrected more perfectly. However, I think my distortion is right, but the edge sharpness is wrong. Nikon has proved many times that they are very professional on the flat field, and this one is the same, and it also retains the normal shooting distance. The field of vision is really large, almost perfect and sharp to the edge, with no coma and no light loss. The visual effect must be amazing. I don't even believe that such a mirror can be made, and I believe that other manufacturers are unable to release similar mirrors.

In 20 13, Zeiss introduced an Otus lens to show its strength, just like saying, "If we don't consider the cost and 3D, let's see what we can make". Nikon WX has done the same thing in the mirror circle, which not only reflects the strength but also encourages the morale, because the sports optical circle is much smaller than the photography circle, which is of course a blessing for Nikon for a hundred years.

My suggestion is that if Nikon really has the courage to produce a 7.5-8 degree 10x50, the field of view should be corrected perfectly, and its performance should surpass any competitor at the same level. Of course, it is more important to make the mirror smaller, lighter and cheaper, so that everyone can accept it more easily. Finally, congratulations to Nikon, except for the mirror WX of Niu X, which opened everyone's eyes.