Chinese Bins

[syed]

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.o:Do:D

[Swedpat]

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

[KorHaan]

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

[etc]

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.

[syed]

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.

[KorHaan]

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

[syed]

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.

[edz]

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.

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

[Swedpat]

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

[edz]

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

[henry link]

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

[edz]

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

[syed]

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?

[elkcub]

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?

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

[Swedpat]

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,

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

[henry link]

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.

[Swedpat]

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

[henry link]

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

[Swedpat]

Ok, thanks, I may understand it now!

Patric

[ThoLa]

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


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

[ThoLa]

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
edz

Within the range of measurement uncertainties affecting the last digit (+/- ab) the transmission values are the same for these glass types. The differences are insignificant.

[Simon S]

This is a great thread with some very interesting information regarding prism design.
From my own experience , I find that the only drawback with BK7 prisms is the reduced overall light transmission. The plus points are there low aberrations and cost.
I have a pair of chinese binoculars that my girlfriend bought me from a charity shop. They are, at a guess 1970's and use high index (BAK4) prisms and have the colour rendition of the Russian binoculars of the time.

[Swedpat]

Simon,

I checked your photos. Really beautiful images! I have bookmarked the page.

Regards, Patric

[henry link]

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

Hi Tom,

This is how I arrived at the 1% difference in favor of BK7. Ed's numbers in post #12 look like others I have seen for internal transmittance through a glass thickness of 25mm. BK7 at 546nm (close to the peak photopic sensitivity of the eye) transmits 99.6% of the light through a 25mm thickness. BaK4 transmits 99.3%. Porro clusters in binoculars have a light path through glass that mostly falls between 70mm and 90mm, so an average 80mm thick BK7 cluster would lose about 1% of the light internally a BaK4 cluster about 2%. I agree that it's not a very significant difference.

Henry

[ThoLa]

Hi Tom,

This is how I arrived at the 1% difference in favor of BK7. Ed's numbers in post #12 look like others I have seen for internal transmittance through a glass thickness of 25mm. BK7 at 546nm (close to the peak photopic sensitivity of the eye) transmits 99.6% of the light through a 25mm thickness. BaK4 transmits 99.3%. Porro clusters in binoculars have a light path through glass that mostly falls between 70mm and 90mm, so an average 80mm thick BK7 cluster would loose about 1% of the light internally a BaK4 cluster about 2%. I agree that it's not a very significant difference.

Henry

Hello Henry!
thanks for the clarification. It's always important to get the assumptions right and precise, particularly so when things get quantitative.
"Clusters" mean the combinations of prisms? (not the entire optical system under the assumption it is made of BK... only)

For those interested in glass aspects I wholeheartedly recommend
W. Vogel
Chemistry of Glass
ISBN 0916094731
Quite advanced but contains lots of interesting information. I guess it's highly valuable for an expert like you (if you don't already have it).
Table on page 9 sums up some interesting properties.

BK glass: refractive index - very low; relative dispersion - very low
BaK: refractive index - high; relative dispersion - low
Flint: refractive index - high; relative dispersion - high

I guess this gives a clue to why glass types are used or not used in certain settings.
I also suppose that the engineers in the better companies (mid-class to high end) know what they are doing.
I think it was you (?) who has repeatedly pointed out that it is important to see the entire optical system as an integrated unit rather than single components. What we see at the eyepiece end is what has been going through all optical elements so I think it is pretty difficult to judge the contribution of the prims at any level that goes beyond the circular/squarish exit pupil.
I am hard pressed to believe that the designers in the developmental departments of our cherished "Toy-makers" are only following a "BaK fashion".

Best regards, Tom

[elkcub]

Tom,

Nicely put.

I think it was you (?) who has repeatedly pointed out that it is important to see the entire optical system as an integrated unit rather than single components. What we see at the eyepiece end is what has been going through all optical elements so I think it is pretty difficult to judge the contribution of the prims at any level that goes beyond the circular/squarish exit pupil.

The reason I repeatedly point out the "coherently coupled" nature of the instrument is that a sophisticated and successful design (read costly) takes advantage of the properties of the various parts to meet demanding performance objectives. The aberrations we perceive at the retina result from the interactions of the objectives, prisms, and eyepieces — as well as the optics of the eye. I know there is a tendency to associate these percepts with one primary source or another, such as the prisms in this case, but in fact it's a composite effect that we see. That the composite effect can be modified significantly through more sophisticated and costly design is exemplified by comparing a standard Swift 804 with an 804ED. They use the same BaK-4 prisms, but the observable CA is remarkably different, and other image qualities are as well. As I mentioned in post #14, and Henry/EdZ seem to agree, in good quality instruments prism glass selection is primarily an effort to minimize vignetting.

Incidentally, even I grow weary of references to the 804ED. It's the only case I know of, however, which can be used as a hands-on demonstration of what's possible through re-design.

Elk

[xiaoming]

Hi everyone:
I have some advices. The bioculars made in China are much cheaper, and the quality depends the money. "Xiong Mao(Panda)" bioculars are the cheapest in China(among the bioculars which can be used in birding, not just a toy). It is about 20-50USD in China. A better one is "SICONG" bioculars, which is about 100-200USD in China.
I think a monocular made in China is much"Wu MEi Jia Lian(High quality and low price)"A
Zeiss one is about 2000USD in China, but a China made one(80mm) is about 150 USD, and a 80mmED is about 300USD. In sunny day, using it to watch waders I can't find much difference with a Zeiss, of course in cloudy or rainy day, it 's not good. I belive it is worth the money.

[elkcub]

In light of the earlier discussion I was looking further into why some low-cost bins use BK7 and others BaK-4. Many sources I've read over the years say that BK7 is cheaper (less expensive) that BaK-4, but that was questioned somewhere on another thread.

One Chinese glass purveyor, New Rise http://www.newrise-llc.com/optical-glass.html, provides an interesting backdrop for understanding optical glass manufacture, of which there are 200+ types. Using Schott glass as a reference, the BK7 equivalent (K9) costs $6, and BaK-4 equivalent (BaK7) costs $8.40. The price advantage of BK7 is 29% — no small consideration for mass produced items.

Glass equivalence is determined by the six digit number code described in an earlier post, not the type name. The latter varies with manufacturer, and leaves much room for confusion. For example, the Chinese BaK4 is the equivalent of Schott PSK3, Hoya PCD3, and Ohara BAL23. However, Chinese BaK7 is the equivalent of Schott BaK4, Hoya ... etc. In addition, using the glass numbers for Chinese BaK7 equivalents, one notes that the Abbe V (last three digits) are also slightly different, depending on the manufacturer. Dispersion, therefore, differs between these "equivalent" products.

I'll leave it to someone else to puzzle out what's what for any given product, but there's ample room for marketing confusion and manipulation with the type names. How to determine optical quality differences between manufacturers is yet another matter.

It's interesting, even if it does make me scratch my head to the pain threshold.

Elk

[ThoLa]

For example, the Chinese BaK4 is the equivalent of Schott PSK3, Hoya PCD3, and Ohara BAL23. However, Chinese BaK7 is the equivalent of Schott BaK4, Hoya ... etc. In addition, using the glass numbers for Chinese BaK7 equivalents, one notes that the Abbe V (last three digits) are also slightly different, depending on the manufacturer. Dispersion, therefore, differs between these "equivalent" products.
Elk

Enter the further complication that the physical properties of glass does not only depend on its chemical composition but CRITICALLY on the cooling regime of the melt during the manufacturing process as it determines the molecular structure of the glass (probably as much as the chemical composition does).

So company X's BaK glass may not be as good as company Y's - hence not "equivalent".

I don't see an easy answer to the initial question.
Tom

[ThoLa]

Tom,
Nicely put.

Elk

Elk,
sorry for having credited the wrong person!
I always appreciate your insightful contributions (even if they complicate "simple" matters, ;), reminding us of the complexities of the real world).
Tom

[elkcub]

Enter the further complication that the physical properties of glass does not only depend on its chemical composition but CRITICALLY on the cooling regime of the melt during the manufacturing process as it determines the molecular structure of the glass (probably as much as the chemical composition does).

So company X's BaK glass may not be as good as company Y's - hence not "equivalent".

I don't see an easy answer to the initial question.
Tom

Tom,

You're forgiven for not remembering who pointed out the complications. I rarely get complimented for that, but I see we think along similar lines. ;)

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.

Harking back to an earlier post, I'm starting to wonder whether or not the "BK7s" referred to here aren't possibly Chinese BaK7, which is the "equivalent" of Schott BaK4. And, by the way, there are other Chinese glass purveyors that use different codes and equivalence tables.

A glow of clarity. I believe what you just mentioned about the manufacturing process and consistency of the molecular glass structure may be one of the most important and salient points in the whole discussion. One could probably build knockoffs using inexpensive but equivalent glass, pay less attention to manufacturing or assembly tolerances, and still lay claim to having made the same thing for less. How might one discriminate the copy from the real thing?, that is the question. One is reminded of Rolex watches. :-O

Best,
Ed

[ajie1a]

The binoculars made in China can up to hundreds Euro/Dollars, from Nikon Monarch series to Fujinon Techonstabil series. It is really expensive. But the binoculars with original chinese brand is cheaper. Nikon Monarch series, Fujinon new series HCF, and original chinese Sicong binoculars looks almost the same. but Sicong binoculars have only half price! The only difference is that Sicong have no Pahsecoating.

The Bak4 or Bk7 is really not a problem. Sometimes a binoculars in 30 Dollar have a Baka Prisma.

[keithdrengen]

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.

Regards, Ronald

We have this 8x40 for sale in Denmark for the equivalent of 79 euro:

http://naturbutikken.dk/index.php?id=articles&a_id=1137

Is that the same one as your 10x50, but in a 8x40 version?

Do you have a picture of your 10x50, or a link to the 8x40 picture you found?

Would be interesting to see if its the same one.

Thanks,

Carsten

[KorHaan]

We have this 8x40 for sale in Denmark for the equivalent of 79 euro:

http://naturbutikken.dk/index.php?id=articles&a_id=1137

Is that the same one as your 10x50, but in a 8x40 version?

Do you have a picture of your 10x50, or a link to the 8x40 picture you found?

Would be interesting to see if its the same one.

Thanks,

Carsten

Hello Carsten,

No, it's not the same.

Here's a link to the 8x40 I found googling JAXY binoculars:
http://www.madeinchina.com/99807/P5769294/wp04-8x40.shtml

These 8x40's are a spitting image of my 10x50's.

Regards, Ronald

[keithdrengen]

OK, thanks anyway though.
Carsten.

[varmintmaster77]

Hello,This question is for henrylink.I have a pair of leupold olympic 8x42 binoculars,and written on the box is bk7 and bak4 is used.Does that mean both is used in the binocular or one or the other?The optical quality in this specific bino is superb for the price...Steve.

[ksbird/foxranch]

While we have been away from forums because we are doing allot of ranch/farm work (20 gallons of mulberries don't pick themselves), I wonder why many binocular manufacturers highlight that their roof prism binoculars use BAK4 prisms, when it is optically inferior, unless they think the market is so stupid that a feature that MIGHT be beneficial for a porro prism binocular, is so ingrained in people's minds that they will believe it HAS to be better for roof prism binoculars too.

I also wonder about the problem of BK7 prisms not being able to pass a wide cone of light properly. I have a couple of pairs of 1949-1952 ultra-wide angle binoculars with what I think was BK7 prisms, but the prisms are about 37mm wide at the opening in the front facing the objective lenses (35mm objectives and F5 FR) and the face of the prism is only about 20mm from the back of the objective lenses. In addition since most of the light path is actually inside the prisms, the eye lenses are very wide (22mm) and the focusing range forwards and backwards is only about 3mm.

In spite of only being fully single coated, these binoculars always seemed very bright (for a 7x35 with an exit pupil max of 5), even though they had 11-13 degree Fields of view. The trade-off was that these were heavy binoculars with huge back grip areas. Compared to a nice 8x30 Deltrintem or 6x30 Kern or Czech military binocular the Bushnell/Korvette/Jason-Statesman ultrawide 7x35s were gigantic. Yet they were very bright and sharp, so perhaps it is possible to make a super or ultra wide bin with BK7 prisms.

And in spite of the problems with a restricted cone of light, Fuji/Meibo made a waterproof porro binocular with center focus 10x50 bin in the 50s with really long barrels, and a rather narrow FOV (6.5 degrees). But I've kept these fully single coated bins to this day because of the sharp image they produce and more than enough brightness, even compared to multicoated models from today.

There is a Carson porro 10x50 and a very similar Carson roofer 10x50 both with incredibly long barrels that use BK7 prisms. And I can't even read the Chinese on the box or binoculars, but I have a pair of very cheap (like $35 delivered) 10x70s that are multicoated and use BK7 prisms that also perform very well and they also have ultra-long barrels. This makes for a large, heavy, difficult-to-balance binocular but on a tripod they work really well.

It is amazing that manufacturer's marketing was able to misrepresent the way that BAK4 glass actually performed since it has poorer light transmission and more dispersion for a slightly lower quality image.

[KorHaan]

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 bought a tripod adaptor a few weeks ago which gave me the opportunity to test both the 10x50 Chinese porro's and my 10x42 Bynolyt roofs tripod-mounted.
The roofs performed better; sharper, more detail, better resolution in short.
This led me to the conclusion that the roofs are far more susceptible to handshake in their performance when handheld than the heavy porro's.
No surprise, in theory, due to the greater weight of the latter.
The thing that did surprise me, though, was the staggering difference in performance of the lightweight roofs, handheld vs. tripod-mounted; I had thought and was convinced I could keep them steady quite well - until I put them on a tripod.

So in fact, the porro's seem to be better when used handheld though the optics of the roofs are superior!

Perhaps when buying new optics it's a good idea to bring a tripod with bino adaptor to test how handshake might influence the views. Now that I realise that I'm using the 10x42 roofs way under their full potential ( without tripod that is) I doubt that I would have bought them as I want them around my neck and not on a tripod.

The good thing is, however, that I love these big porro's all the more. I have them four months now.

Regards, Ronald

[Renze de Vries]

Ronald,

Next to the mass factor, difference in perceived image size could contribute to unsteadiness as well in my opinion.
It's well known that roof binoculars, because of their objectives being in line with the oculars, give the impression of a larger image (object) size in comparison to porro binoculars, where the objectives are set wider apart than the oculars. Of course this is an illusion - the brain is 'led to believe' that objects are smaller in the porro view - in the way that magnification is not altered (8x is 8x, be it in a porro or a roof) but it is also 'real' in the sense that we 'see' this difference in image size and will be affected by it. My impression is that most people are pleased by the image size effect of roof binoculars in comparison to porro's because the image is more spectacular. However, if the image is perceived as larger, wouldn't displacement of the image be perceived as larger as well? Isn't it logical to assume that the unsharpness caused by our trembling hands is more easily noticed in a roof binocular? And perceived as less troublesome in a porro type binocular?
Just a thought.

Renze

[marcus]

Where you said that more people are pleased with the image size affect of roofs in comparison to roofs, I assume that you meant in comparison to porros, right?
I'm not saying that roofs are better, or anything like that. I'm just clarifying your comment.

[Renze de Vries]

Thanks Marcus, my error indeed. As I could still edit the text, I did. So now it reads as it should (and your, very welcome, comment has turned incomprehensible, excuse me).

Renze

[Renze de Vries]

I decided to give the shake-image size issue applied to porro vs. roof binoculars a thread of its own.

Renze