Kunming United Optics Corporation BW8 design family includes ED bins (2 Viewers)

[Kevin Purcell]

The other interesting thing I found on the United Optics web site

This seems to be recent (February 2008) according to the news.

The BW8 Series comes in an ED and non-ED varients.

Which have the same specs except presumable less CA with the addition of ED glass (LaK - Lanthanum Crown? Which one?) I presume as a single element in an objective.

e.g http://www.osicotech.com/products/optical_glass.php

The model range is:

8x32ED/8x42ED/10x42ED/8x48ED/10x48ED
8x32/8x42/10x42/8x48/10x48

They're a "closed" bridge/hinge design so they're different from Promaster and Hawke ED bins.

Specs seem the same for both ED and non-ED. Not too wide.

8X32 #BW8-0832 ED
393 ft @ 1000 yds
ER 16mm
BAK-4
FMC
725g (26oz)

8X42 #BW8-0842 ED
367 ft @ 1000 yds
ER 17mm
BAK-4
FMC
780g (28oz)

As seems common today the 42mm is not that much heavier than the 32mm (about 55g or less than 2oz).

Optical Quality
1. Whole quality is better than our MS binoculars, 6 group and 10 elements, 5 elements eyepieces, including two pieces exotic LAK glasses, objective lens is 3 elements, focusing lens is 2 elements.
2. Extra flat field and distortion free, edge to edge sharpness
3. Clever design and eliminate chromatic aberration, color free APO version is designing also
4. High quality fully multi-coated
5. BAK-4 prism and phase coating for amazing resolution, dielectric coating for maximizing reflectivity of the roof prism.
6. Wide field of view

Mechanical Quality
1. Main body is alloy aluminum, light and durable, compact size
2. Diopter lock
3. Silk smooth 2-3 stages twist-up eyecups
4. Waterproof and nitrogen gas filled.

http://www.united-optics.com/produc...Birding_Outdoor_Binoculars/BW8_Series/BW8.htm

Do these ring any bells with anyone? Is anyone selling them?

Searching around I don't find any obvious candidates.

 

[henry link]

Kevin,

The only ED glass on the Osico page is the stuff they call FK2 (Abbe 84.48). None of the LaK series glasses are ED. All have Abbe numbers of around 60 or lower. You might find this thread on the subject of Chinese ED glass interesting:

http://www.astromart.com/forums/viewpost.asp?forum_post_id=627838&poll_id=&news_id=&page=

Roland Christen (Astro-Physics) frequently posts interesting information from an insider's point of view at Astromart.

Henry

 

[Kevin Purcell]

Thanks for the link, Henry.

Unfortunately it requires a $12 registration fee for new accounts. Could you give a summary or a repost?

I didn't realize that there was a formal definition of ED based on the Abbe number. So an ED glass requires an Abbe number of 80 or more.

So does this mean that these are not ED bins?

Does this raise a bigger issue with other Chinese ED bins?

How do we know if we are really getting ED glass?

 

[NWBirder]

Kevin, I looked at your original post. I don't think they imply LAK glass is ED glass. It seems ED glass is a separate option. BTW, what's LAK glass any way? I presume it might be something between regular glass and ED glass? What's Abbe number? I guess I don't really want to know that, but being poked by the curiosity side of myself.

 

[Kevin Purcell]

You could be correct. The page could just be written in an ambiguous manner with a bunch of phrases connected by commas: a full stop or colon would help. e.g. the phrase could be "5 elements eyepieces, including two pieces exotic LAK glasses." in which case they're using LaK in the eyepiece.

So for the ED models they could be using both LaK and ED glass though the only "exotic glass" actually mentioned is LaK. And I would consider ED glasses to be pretty exotic.

I'm sure it read better in the original Chinese.

Note they also "objective lens is 3 elements" i.e. I think they're making a semi-Apo or perhaps Apo design in the objective (so they bring three wavelengths of light to focus rather than the two for an achromat). That's a nice idea.

I'd still love to know if these are in retail anywhere.

LAK is Lanthanum Crown (LaK)

See this very nice Abbe Diagram divided up into "territories" (including ones you might recognize like BK and BaK)

http://en.wikipedia.org/wiki/Image:Abbe-diagram.png

You can see that LaK glasses have a similar Abbe Number to BaK but a higher refractive index (so they bend light more readily so you can make thinner lenses with them or include them in other lens designs).

The Abbe Number is well described in Wikipedia. In handwaving way it describes the dispersion: the tendency of a transparent material to refract light of different wavelengths by different amounts. A lower dispersion means the different wavelengths are refracted more similarly and so you get lower LCA.

http://en.wikipedia.org/wiki/Abbe_number

Abbe numbers actually matters if you wear glasses.

Crown glass (i.e. ye olde eyeglass glass) and old, cheap (but good) CR39 plastic have decent Abbe numbers (almost 60). The newer ophthalmic lens materials have lower (in some cases much lower Abbe numbers) and lead to eyeglass lenses with much more stray color. The worst case is polycarbonate which whilst tough and resistant to most solvents (so it's good for lab safety eyeglasses) has the worst stray color. It should be avoided in a birding eyeglass.

CR39 is the best bet for a birding eyeglass: cheap, good color but can be thick in strong prescriptions.

 

[NWBirder]

Thank you for the explanation. I know most of decent+ binoculars use BAK4 prism. How about their lenses? Are they BAK4 too?

It seems there is an inverse relationship between refractive index and Abbe number from your reference on wiki. Does that mean ED glass like FK2 has lower refractive index, hence longer focal length (can I come to that conclusion?), therefore less chromatic abberation. No wonder my unaided eyes perform better than the best ED glass because the air has refractive index of 1.0. Is this the reason all the high end binoculars like Swarov EL all have long body length because of longer focal length from ED glass?

 

[henry link]

Thanks for the link, Henry.

Unfortunately it requires a $12 registration fee for new accounts. Could you give a summary or a repost?

I didn't realize that there was a formal definition of ED based on the Abbe number. So an ED glass requires an Abbe number of 80 or more.

So does this mean that these are not ED bins?

Does this raise a bigger issue with other Chinese ED bins?

How do we know if we are really getting ED glass?

Sorry, Kevin. I didn't know about the registration fee.

In the thread Roland Christen says that a Chinese glass company, CDGM, has been making large quantities of an ED glass called H-FK61, which they sell for "a very low price comparable to normal optical glass". He describes it as being a "first generation ED glass similar to Ohara FPL51" which has an Abbe number of about 80. He claims that this glass is used in nearly all the inexpensive Chinese ED refractors flooding the astronomical telescope market now. I imagine there's a very good chance that this same glass is used in the inexpensive Chinese ED binoculars. As for the Lanthanum glass, that's probably in the eyepiece.

Thanks to the low focal ratios there is actually plenty of longitudinal chromatic aberration in binocular optics whether ED glass is used or not. It's just not visible as a color fringe because the magnifications are so low and in daylight we're usually using only a small central area of the objective.

Henry

 

[Kevin Purcell]

Thanks for the info, Henry.

So we should expect to see more ED bins from China, I think.

BTW, I asked the United Optics if they could tell me if anyone is OEMing this family for sale in the USA and of course he demurred (as one might expect). I asked him to forward my email to any client who may contact me directly. I won't hold my breath for a reply but you never know.

 

[edz]

I tested the 8x42 version of this model line. Frankly, it was rather poor.

Effective aperture is 8x34
field stop was not at focal plane, so was out-of-focus
Boosted resolution one of the poorest marks ever recoreded for any binocular.
beam transmission was actually the lowest ever measured.
Beam balance was tilted 20% off-center

After discussion with the supplier from whom I boughht this test model, he stopped carrying this line.

edz

 

[NWBirder]

Boosted resolution one of the poorest marks ever recoreded for any binocular.

edz

edz, are you saying the resolution on this binoculars is very poor? I am curious whether ED glass makes any difference there. thanks

 

[edz]

I'm sure the models I tested were NOT any special glass. That would be an option on these binoculars from Kunming. All I posted above was on a normal glass version. Yes the resolution was very poor. So were several other tests, both mechanical and optical. I would not invest in ED glass in this particular binocular housing.

This BW8 roof is poorly designed with an internal baffle near the prism that stops the aperture down to 35-36mm. Then in addition to that the prisms are too small to span completely across the prism aperture, so it looses another 4% of aperture arera. The effective aperture is only 34mm. On the sample I tested, it appears the prisms were uncoated.


Read my CN review of the 42mm roofs and you will see this series 8 binocular.

edz

 

[NWBirder]

Ed, I am not sure whether I found the right page http://www.cloudynights.com/item.php?item_id=1771

The only one with 34mm effective aperture is Oberwerk 8x42rp. It does not look like the BW8 series, as it weighs only 680 g vs 750 g for BW8 from OP's link. From the picture, the old oberwerk 8x42rp looks very much like an old Bushnell Trophy. Again, I might not be looking at the right binoculars in your report.

Maybe it is BW2 series? I found this from Kevin's original link

http://www.united-optics.com/produc...Birding_Outdoor_Binoculars/BW2_Series/BW2.htm

Thanks for pointing us to the right source. It's amazing how deep and broad you have over there on CN.

 

[Kevin Purcell]

Well, that's a disappointment.

Seems odd that they would offer a ED version of such a poor bin.

The other thing I notice is a quote from the review: "The Oberwerk 8x42 is 5.8°" (i.e. 304 feet @ 1000 yds) but the HW8 specs above do not match this at 367 ft @ 1000 yds or 7 degrees.

The weights quoted for the Oberwerk 8x42 and the non-ED HW8 8x42 are 60g (3oz) different (681g versus 745g).

The ER is different 14mm versus 17mm for HW8. Though I see in the review you quote the Oberwerk as speced at 20mm ER.

In the review you say: "one eyecup constantly changed position needed to reset it every time I used it." but the BW8 has stepped eyecups (2 or 3 stops) but you don't mention it.

That's a significant number of differences.

http://www.oberwerk.com/products/srpseries.htm
http://www.united-optics.com/produc...Birding_Outdoor_Binoculars/BW8_Series/BW8.htm

Plus your review is dated March 20008 and these bins were introduced by United Optical in Feb 2008. Did they really get to the end users that quick?

So that begs the question "How do you know they are the same bins?"

No doubting the review but I'm perhaps doubting the mapping to the BW8. Perhaps they're reusing the same enclosure.

I suspect these are United Opticals BW2 just from a look at the spec and the pictures (though even those specs don't quite match up ... the FOV is too narrow).

<http://www.united-optics.com/products/Hunting_Birding_Outdoor_Binoculars.htm>

Clearly the bin you reviewed is a dog but it doesn't seem to match-up with anyhere. Though perhaps their previous bins explain the apparent absence of this in in the US market?

An aside: the United Optics BW9 look like the share the same enclosure (and perhaps some design) with the Xi'an Sciong Navigator (i.e. the Garret in your review). Difficult to tell them apart without looking at the specs.

EDIT: Ah ha! I see NW Birder came to the same conclusion whilst I was researching and writing this post. Clearly my telepathic wave can extend over a city (or perhaps it's HIS telepathic waves extending to me!)

 

[NWBirder]

EDIT: Ah ha! I see NW Birder came to the same conclusion whilst I was researching and writing this post. Clearly my telepathic wave can extend over a city (or perhaps it's HIS telepathic waves extending to me!)

I am glad I am not the only one who was puzzled. As kevin, I have no doubt about Ed's review. The mapping is the one in question.

That's a significant number of differences.

http://www.oberwerk.com/products/srpseries.htm

I think this link is their newer rp series. The one Ed reviewed is different. It had 19 ft close focus according to Ed's article. But this one has 8 ft close focus. I remember seeing one of those old one reviewed by Ed on ebay before. It had a weird shaped metal bridge over the focus wheel, exactly like an old Bushnell Trophy 5-6 years ago. Maybe oberwerk discontinued that model after Ed's feedback and changed to the current one.

 

[Kevin Purcell]

Maybe oberwerk discontinued that model after Ed's feedback and changed to the current one.

One can only hope. But the whole of edz review sounds like one of a "crappy" Chinese bin designed a few years ago. It makes one wonder why they didn't notice how bad it was when building it.

Seems rather like my Promaster 7x32 review (which I still haven't posted here) though that one was less "just crappy" and more "trying quite hard but not succeeding".

I wonder if United Optics have anyone carrying a BW8 derived bin (especially the ED bins) in the USA?

 

[edz]

the Kunming thread in reference to 36mm compares to the Oberwerk sport RP, not this thread. I mentioned the sport rp in that thread. the binocular in my CN 42mm roofs is not the sport rp, it is an older model. I may be mistaken in mapping it to the BW8 (is that this thread).

edz

 

[Kevin Purcell]

Got it, edz.

This is the BW8 thread (apologies for the occasional HW8 usage ... that bleed through from another hobby ... it's a well known Heathkit radio ... and is in my muscle memory).