Chinese Bins (1 Viewer)

Anyone having any experience with chinese binoculars.
Well we all would liketo go for the branded ones but how about trying a chinese copycat bin.oo

Syed,

Since several years the big japanese brands like Nikon, Pentax, Minolta, and more produce their low and midpriced binoculars in China. Chinese binoculars are very high value for the money today, the best of them is rivalling the best japanese and europan brands.

But there is still a lack in the quality control, if your are lucky you will get an excellent example. If you are unlucky you will get a worse example.

There are companies who sell chinese binoculars and have their own quality control, however. As you will notice of the design, the most of them are from the same fabric in China.

Here are two of them, both of them well reknowned:

http://www.oberwerk.com

http://www.garrettoptical.com/



Regards, Patric

Hi Syed,

A convenience store just around the corner had some big Chinese 10x50 porro's.
Just out of curiosity I had a look through them, and within a minute I plunked down € 60 and took them home. Must have been the fastest purchase of any pair of bins in my life, but the views I got made me want to own them.
It's been 25 years since my last pair of porro's, always had roofs, but I immediately liked the feel of the big, clunky Chinese beast, and the images I got were the best I've ever seen. Note that I recently sold my Zeiss 7x42 FL's, after 20 months of trying but only scarcely finding a truly relaxed view I gave up on them. The Chinese porro's instantly gave a fine relaxed view, and after nearly two months they still do; my eyes seem to have found their state of Nirvana, in fact the view reminded me of the Nikon Venturer 10x42 I once looked through a decade ago. Should have bought it then, because the LXL's don't give me that relaxed view. I wonder if the former Venturer and these Chinese porro's share something no longer to be found in modern binoculars: lead containing glass. Could the lead in the glass be responsible for that relaxed view?

Anyway, as good as the views were, the other features of the Chinabeast were somewhat of a disappointment; close focus is no less than 8 metres, it's not waterproof though a tight fitting rainguard is provided as well as tethered objective covers. Though useless, these covers are perfectly made, fitting snugly inside the objectives' rims. Way better than the covers of the FL's. Another anomaly are two diopter settings on both the oculars. Finetuning is very easy this way. The only other pair of bins I know of to have two diopter settings is the new Steiner. Focussing is firm but smooth, and without slack, the focus wheel being centrally placed on the hinge, a small distance away from the eyepiece end which allows for focussing under the rim of a baseball cap, if it's raining. The broad housing forces me to focus with the tip of my left middle finger, my right hand holding the bins near the objectives. It's surprisingly steady for a 10x, probably due to the weight of 985 grams. That's another issue that I'm currently trying to tackle, to make some sort of comfortable strap arrangement. The strap provided was way too thin so I changed that for an OpTech comfort strap.
The Chinese porro's outperform my 10x42 Bynolyt roofs in every aspect, optically. Strange, but true. After nearly two months of using them the view amazes me every time when I'm out birding. There is a threaded tripod attachment on the far side of the hinge, I've got to have a tripod adapter to mount them and use them for raptor watching. The FOV is 6.6 degrees, as it states on the bins, and it shows; a nice, wide image, sharp to the edge, but sharpest in the center. Depth of field is spectacular, way better than my 10x roofs; from 10 to 100 metres sharp requires only a minor movement of the focus. The possibility to focus past infinity is gross, nearly a full turn of the focus wheel. I would have liked that to be less in favour of a better close focus, but now I can see without my glasses even beyond infinity.
The coatings on the eyepieces are blue, on the objectives pale green. I've only cleaned them a few times, and they seem scratch resistant.

The brand is Xinxinxin, or Gingingin, written on the left in a rather awkward style so I'm not certain I have that right. I tried to Google the brand name, but the nearest I came was a " JAXY binoculars " website; searching there I did not find my 10x50's but to my surprise DID find a spitting image in the form of a 8x40.
I had one hit with Gingingin 10x50 on a Norwegian forum. I couldn't understand a thing so that appeared to be a dead end. It's a pity, because I wanted to have more info on the stated "long eye relief " written under the brand name on the bins.

To conclude, I can only say these chunky bins are a joy to own, for a mere 60 euro's.
The bag that came with them is an unpadded, soft, tight, and not very trustworthy item.
I suppose that is fair for the amount I payed. But the peculiar thing is, I now have a 60 euro bin on a 30 euro strap.
My original intent to get me a Canon Image Stabilized pair of binoculars is completely out the window, well, until next year at least. I'm just glad that I finally found a pair of bins my eyes are comfortable with.

Regards, Ronald

I looked at something similar here in US, in walmart.

They were better than I thought optically.

Problems where: Insufficient IPD, and poor eye relief. I have a pretty small IPD and wear glasses.

If you can work around these, they are a good deal.. about 100USD. or less.
What ever the brand was.

Thanks Ronald.
I think you have increased my interest in chinese bins.
Why pay five times when you are getting more or less the same for much lower price.
But still wonder that the prisms used in most of them are BK7s.
Recently checked a 10x60. Quite pleasing view I think.

Hi Syed,

Forgot to mention that the Chinese 10x50's have a warm colour cast, which I found to be pleasing. I'll take them out one of these days to check their twilight performance; early spring gives the opportunity to watch Woodcocks near the nature preserve in the vicinity here. I'll take my 10x42 roofs as well, to compare. These boast a 60 layer multicoating on the prisms, so it could be interesting to use them aside with the porro's in low light.
Do you know for a fact that the prisms used in Chinese bins are BK7s, or is that a guess?
I've understood here on BF that BK7s are better than BAK4s.
My intention is to go looking for Chinese giant binoculars, like 20x80 porro's, for sea watching; if these are as good as the ones I've got it must really be a joy to use them for that purpose.
Wow! I've had Swaro, Leica and Zeiss in the past, it's unbelievable how good these Chinese porro's are. China is a big promise!

Regards, Ronald

Hello Ronald,
The fact of the matter is that Bak4 prisms are optically superior to standard BK7 prisms.
In BK7 prisms the exit pupil is not completely circular (actually the edges of the circular
pupil are intersected by straight lines forming a gray area and when you look at the exit pupil you will find a square within a circle. That's a BK7.)
On the other hand the Bak4 prisms have perfect circular exit pupils. This gives them a bright view even at the edges of the field of view.
So check out for yourself what type of prisms your chinese bins have .
I myself have found that perhaps most of chinese bins have BK7s (as Bak4 would prove to be expensive).
A user having more experience of chinese bins may tell about that more.

syed said:

Hello Ronald,
The fact of the matter is that Bak4 prisms are optically superior to standard BK7 prisms.
In BK7 prisms the exit pupil is not completely circular (actually the edges of the circular
pupil are intersected by straight lines forming a gray area and when you look at the exit pupil you will find a square within a circle. That's a BK7.)
On the other hand the Bak4 prisms have perfect circular exit pupils. This gives them a bright view even at the edges of the field of view.
So check out for yourself what type of prisms your chinese bins have .
I myself have found that perhaps most of chinese bins have BK7s (as Bak4 would prove to be expensive).
A user having more experience of chinese bins may tell about that more.

Click to expand...

The fact of the matter is the BK7 glass is superior to BaK4 glass. However in the very fast f/4 application of almost all binoculars BK7 cannot handle the light cone as well as BaK4 glass. Therefore it is a compromise. In order to handle the light cone without vignette BaK4 glass is used. But this poses other problems. For instance BaK4 glass intoduces more false color into the image. For the very long light cones of binoviewers, BK7 is preferred. Also FWIW, a proper apllication of BK7 in a binocular, since the BK7 prism would need to be so much larger, would make the BK7 prism more expensive.

FWIW, I haven't seen BK7 in any binocular I've purchased in the last 10-12 years. I've bought and sold 30-40 Chinese binoculars in just the last 5 years. Not one has had BK7 prisms.

BK7 is not inferior glass, Chinese binoculars are not prevalent with BK7 prisms and BaK4 is not more expensive.

This is from another article I wrote on prisms:
Anyone whishing to understand the applications of BaK7 and BK4 prisms should read everything that Roland Christen has published on the subject.

BK7 glass is probably one of the best glass in the world for prisms, however is not particularly well suited for the light cone from a fast lens. For this BaK4 performs equally well.


BaK4 (Barium crown) has no advantage over BK7 (Borosilicate) when used in in a situation where the incoming light beam angle is very narrow. However in wide field applications such as low power binoculars there are advantages - increasing the brightness of the edge of field while having no effect on the on-axis image. There would be no advantage to BaK4 over BK7 to any part of the image for instance in a Binoviewer because of the narrow beam angle where generally they are slow systems without wide fields.

The disadvantages of BaK4 is that it introduces more spherical aberration into the optical path than BK7. BaK4 also introduces more chromatic aberration than BK7. You may not notice this if your optics are poor to begin with.

BK7 is the clearest, most defect-free optical glass available for prisms. BaK4 is close, but not quite as good. That's ok for low power applications of a typical binocular, but not for high power low contrast situations seen in telescopes. For a high powered high f# telescope, with a very narrow light beam, BK7 would be a better choice for a prism. Similar applications are found in binoviewers.


edz

Hi Ed,

What you are telling is actually a big surprise to me, and it's the first time I have heard it. Accordingly, the only reason BAK4 prisms are chosen for quality binoculars is because they provide an exit pupil free from vignetting.
According to the usual selling arguments of binoculars I have actually got the incorrect impression that BAK4 is optically superior in any respect!

Regards, Patric

BaK4 is not used for binocular prisms because it is superior glass. It is used because it is better able to handle an f/4 light cone. If BK7 were made large enough (wider prism aperture) to allow the passage of the entire light cone without internal vignette, it would be the better glass prism. But then it would a much larger prism, the binocular housing would be larger and it would be heavier.

Some of the best binoviewers in the world are made with BK7 prisms because they are intended to be used with a light cone in a binoviewer of generally f/10, in which case the prisms can be made smaller. Some of the best prism diagonals are made with BK7.

The disadvantages of BaK4 glass prisms as noted above are that it increases spherical aberration and chromatic aberration. The advantages are, those aberrations may not be prominently seen at the extremely low powers of binoculars, and you get an unvignetted light cone. It certainly has nothing to do with which glass is more expensive.

This is not really new information. There are internet discussions relative to this topic going back quite a few years. I suggest referencing work written by Roland Christen, one of the foremost optics designers of the last 20 years, owner of Astrophysics.

edz

Ed,

I agree with everything you said except the part about larger BK7 prisms being able to handle an f/4 light cone. It's the refractive index of the glass that prevents full transmission of the part of the cone outside about f/5.5. Increasing the size of the prism wouldn't help since the refractive index would remain the same. It's a shame that BK7 has been so demonized by binocular marketers. Except for brightness when the full exit pupil is utilized, the image quality in most binoculars would probably be improved by replacing the BaK4 prisms with BK7.

Henry

Thanks Henry for that correction.

Also, I dug this up. In addition to the elimination of CA and SA, BK7 has greaster transmission.

Internal transmittance at various wavelengths (in nm):
BAK4: 700nm: 0.996, 660nm: 0.995, 620nm: 0.994, 580nm: 0.993, 546nm: 0.993, 500nm: 0.992, 460nm: 0.991
BK7: 700nm: 0.998, 660nm: 0.997, 620nm: 0.997, 580nm: 0.996, 546nm: 0.996, 500nm: 0.996, 460nm: 0.994

The Abbe Number of a particular glass type refers to the reciprocal value or dispersive power of the material. A higher Abbe number indicates that less chromatic dispersion occurs for light passing through such a material. This would indicate a superior common focus and less chromatic aberration due to unfocused light of various wavelengths.
Abbe Number of BAK4 Glass: 56.1
Abbe Number of BK7 Glass: 64.2

edz

Then someone please explain
Why the giants from fujinon have BAK4?
Why the giants from oberwerk have BAK4?
And almost any expensive bin from a big brand mentions "BAK4".
Are they all wrong at the same time?

syed said:

Then someone please explain
Why the giants from fujinon have BAK4?
Why the giants from oberwerk have BAK4?
And almost any expensive bin from a big brand mentions "BAK4".
Are they all wrong at the same time?

Click to expand...

Except for Henry's brief comment, it may not be particularly evident from the discussion that optical glass has two essential properties in design: an index of refraction and an Abbe V number, the latter of which gives the dispersion relative to refraction (the amount of bending that a light ray undergoes). For visible-spectrum glass, the V-number is defined as the refractive index at a mean wavelength (helium d line), divided by the difference in refractive indices between short and long wavelengths (hydrogen F and hydrogen C lines). This ratio is referred to as the inverse of dispersive power, but the important point is that dispersion is expressed relative to refraction. A two dimensional plot with the mean refractive index shown on one axis, and the (non-independent) Abbe V number on the other, locates a particular glass within this two-dimensional conceptual framework.

There are many glass types to pick from that could influence final performance. Frankly, I don't think we consumers really get to know which ones are used in any given instrument, and the dichotomy between BaK-4 vs. BK7 has probably become a convenient but somewhat misleading marketing simplification. For those who build their own telescopes the situation is markedly different, of course, because they get to pick not only the glass for their own applications, but also their own applications.

Several parameters in binocular design can be manipulated to correct (compensate) for the CA/SA contributed by the prisms. In the end a holistic instrument is produced, however, and not a collection of individual pieces. Without complex math models, moreover, no one can readily predict the performance of the total system just by knowing the performance of the individual parts. In such fully-coupled, coherent optical systems, aberrations interact between the components, sometimes canceling and sometimes reinforcing each other. CA and SA are particularly subject to this complex interaction effect, and, in fact, the optics of the eye itself (exclusive of the retina) also become part of the coupled system. Its aberrations interact with those of the instrument.

Vignetting, unlike optical aberrations, is essentially a geometric issue that imposes a boundary constraint on the refractive intex, and this largely limits the glass types that are appropriate, i.e., the right area of the glass chart mentioned above. Assuming that CA and SA are properly corrected, however, I for one am not persuaded that an instrument with BK7 prisms intrinsically produces a better quality image at the retina than one using BaK-4 (or 1 or 2). One can not reason from the properties of the prism glass independent of the design of which it is a part.

So, to finally answer your question, BaK-4 glass shows up in high-end products because it best meets the design objectives. Apparently, most companies have come to the same conclusion. I can't imagine why lower-end products use BK7 prisms if not for the price advantage or some other factor related to manufacturing costs.

Blue skies,
Elk

syed said:

Then someone please explain
Why the giants from fujinon have BAK4?
Why the giants from oberwerk have BAK4?
And almost any expensive bin from a big brand mentions "BAK4".
Are they all wrong at the same time?

Click to expand...

Syed,

Your questions are highly justified!
It is one thing if BAK4 are used in "normal" binoculars when it's important to get a binocular of a suitable size and weight.

This isn't the case with the models of large astronomy-binoculars (some of them aimed to be specific tripod mounted), however.
The difference of size and weight has to be quite insignificant if a 20x80 or 25x100 uses BAK4 or Bk7 prisms! If the Bk7 really had been optically better I am sure that brands like Fujinon and Miyauchi had used them. But they use BAK4.

Also the Miyauchi 25x141mm and the worlds largest binocular Fujinon 25/40x150 use BAK4. The difference of as well weight and price would be (percentually) insignificant using Bk7 instead, and a true optical improvement by using Bk7 would make them justified to use it.

Regards, Patric

BAK4 is used in high quality binoculars for one reason only. It can transmit the entire light cone of an f/4 optical system. The one and only disadvantage of BK7 as a binocular prism glass is that it will not fully transmit the light from the outside part of a light cone if the optics are faster than about f/5.5. That's what causes the familiar square shadowing at the outside of the exit pupil in binoculars that use BK7 glass. Prism size (or binocular size) doesn't matter at all, only the focal ratio of the optical system.

Full transmission of the part of the light cone outside f/5.5 has one obvious advantage when the eye is open wide enough to accept the full exit pupil. A binocular with BAK4 prisms will be brighter than an identical binocular that uses BK7. But the BAK4 binocular will also suffer from higher levels of chromatic and spherical aberrations because all the extra light the BaK4 prism transmits comes from the outside edge of the light cone. Every binocular has lower aberrations when it is stopped down to eliminate the light from the edge of the fast f/4 light cone. In daylight, even the brightness advantage for BAK4 disappears if the stopped down eye limits the effective binocular focal ratio to something above f/5.5. Then a BK7 prism actually transmits slightly more light (about 1% in a typical size Porro cluster) because BK7 glass is more transparent.

As far as I can tell BK7 is held in such contempt that it has virtually disappeared, even in cheap binoculars. I don't think anyone has to worry about seeing it in any expensive binoculars. Ironically, the reassuring BaK4 prisms in those cheap Chinese binoculars may be totally uncoated (even if the binocular claims to be "Fully Multi-Coated" ) causing a 20% light loss under all lighting conditions and the prisms are sometimes so undersized that the true aperture of the binocular may be as much as 20% smaller than specified. Those are the things to beware of in cheap binoculars these days, not BK7 glass.

Henry,

I understand what you are saying. But isn't the ability to transmit the light mainly depending of the SIZE of the prism? I mean that if the size of the prism is adequate it ought to transmit the entire light anyway? Just wondering, don't know...

Regards, Patric

Patric,

It's the angle at which the edge of the light cone strikes the prism face that causes the light loss, not the size of the prism. No matter how large a BK7 prism is made it will always show the same shadowing at the edge of an f/4 light cone, even if the prism is much larger than the light cone.

Henry

Ok, thanks, I may understand it now!

Patric

henry link said:

Then a BK7 prism actually transmits slightly more light (about 1% in a typical size Porro cluster) because BK7 glass is more transparent.

Click to expand...

A statement that is in conflict with the numbers given in #12.