Kowa BDII-XD - september 2019 (2 Viewers)

18000bph said:

Troubador, can you get your German Kowa contact to clear up the focus wheel material question with regards to the BD? Seems strange to me that they would use metal for one and plastic for the other but end up with an almost indistinguishable product.

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I have asked the question and expect an answer on Tuesday but it would really not be very strange at all if the 'family resemblance' of a silver focus wheel was maintained across different product ranges while the materials used to achieve this are changed according to the price point that the products are sold at.

Lee

42za said:

Yeah , the focus wheel on my old BDXD Prominar is plastic , the BDII's are most likely plastic as well , although they do LOOK like aluminium , I tested this with a metal detecting pointer.

Cheers.

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The Kowa BDII XD's focus wheel is plastic. Most binocular focus wheel's are plastic aren't they? I think the SV's and the SF's are plastic. One advantage of a plastic focus wheel is it is warmer on a cold day than metal.:eek!:

dries1 said:

I tried it a bit today while out in the field, some sneak peeks.

Now this is the 8X32 - not the best for glare, not one of the strong points.
The sweet spot is if I were to put a % on it maybe 30%, the edges can be focused but only at the edge, slightly off the field stop it becomes out of focus.
To be clear these will be a great truck glass for me, though a porro, the EII is still the king of the wide FOV.

The depth of field is OK from 150 feet to infinity, but any closer it resembles in visual observation as a flat field, no depth of focus, or significant depth of field. There is significant pincushion distortion.
The FOV is wide, and it is well built, good grab and go econo glass for the money.

The 6.5X32 is likely different.

Andy W.

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"The EII is still the king of the wide FOV"

The EII is a great WF binocular but one area where these Kowa's have an advantage is contrast. Contrast is the EII's weak spot and these new Kowa's IMO have better contrast. At least my Kowa 6.5x32 does when comparing it to my Nikon 8x30 EII. Of course the EII kills any roof on 3D just like any porro will decimate a roof.

My take on the 8X32.
Decent glass for the money, water proof yes, however if I had to choose between it and an EII, it is an EII every day. Selling points of the glass.
1: All indications are that the build quality is good, (modest priced glass from China have been lacking in this arena for a while, however it appears that Kowa, a reputable company, has been able to control QA/QC, we will know more going forward, they also have a good Warranty.
2: A wide FOV for a roof.

As others who have owned viewed a few 8X30s/32s, view the Kowa 8X32, more opinions will be available.

Andy W.

Hi Folks,

Curious to know the difference between the old and the new BDII XD model besides wider FOV.

Has anyone tried the 6.5 x32 for astronomy

I will try mine tonight if it's clear out. It would be great for wide field views of the Milky Way but as it get's a little soft on the edges you wouldn't get perfectly flat star fields with no distortion like you would with a flat field binocular. It is a really bright binocular in low light due to the big exit pupil and I think Kowa used some pretty good glass and coatings on it for the price. I like it. I am anxious to see how the Kowa 10x42 performs with it's 72 degree AFOV. I wonder if it will compare to the Nikon HG 10x42? The HG's have a 69 degree AFOV and their edges are a little soft also and they are 2 oz. heavier. That could be a little bit too much of a price spread! These new Kowa's IMO are very good performer's for their price point and even a little above. If you like a big FOV and don't want to spend a lot of money they are an excellent choice in a nice small compact roof. They are small, light and they are made of magnesium instead of plastic. As Dries say's the quality is very good for MIC especially. The 6.5x32 is really good for close in fast moving birds and it work's great on butterflies. With that big FOV and great DOF you can pick them up easier! I am surprised how good the DOF is on the 6.5x is. You probably have 100 yards of depth where everything is in focus. It helps! Another I like about the Kowa's is their compactness and lightweight. They are much smaller and more compact than most 32mm and 42mm binoculars. The 32mm only weighs 18 oz. and the 42mm only weighs 22 oz and they are small. I also like the minimalist approach they take to armouring the binocular. The armour has a very nice quality feel to it. They don't slip out of your hands but they don't have that sticky feel that some binoculars have especially the less expensive ones. The armour protects the binocular but it is not overdone. I am sure this approach to armour helps keep the weight of the binocular down also and it gives the binocular a very quality look for this price point. The armour covers every square inch of the binoculars so there is no area that could be prone to getting scratched or having the paint rub off. I like the look of the Nikon Monarch HG's but there are unprotected painted areas on them that could be scratched or might be prone to abrasion. The paint and finish and build quality is flawless also. Almost, like an alpha.

Swedpat said:

Thanks for explanation.
Several years ago I have in some thread wondered about the difference if comparing different AFOV with the same magnification and aperture for stargazing. For example: two 10x50s, one with 50 deg AFOV and the other with 65deg. My thought was that with the narrower FOV less stars will be visible and therefore less light amount hitting the eye. I don't think stars will impact pupil size in a binocular but could a narrower field improve dark adaption for dim objects?

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I don't think there would be a difference when viewing the night sky, because your pupils would already be fully dilated. The issue with low-light viewing occurs while your pupils are dilating. The dilation process starts earlier and finishes earlier with the 10x. Once you have full dilation using either 8x or 10x, light from your subject will be the same again: same aperture, same glass, same coatings, same transmission factor.

outbackmaster said:

Hi Folks,

Curious to know the difference between the old and the new BDII XD model besides wider FOV.

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Improved glass and coatings give a huge increase in light transmission. This was the first thing we noticed when comparing them side by side.

Swedpat said:

Hi Steve,

I find this very interesting. With 8x the image brightness is ~56% brighter than with 10x, so I have always claimed that 8x is better than 10x in low light.

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This stuck in my head and I had to come back and respond to it.


That 56% difference is in the size of the exit pupils. 5.25^2/4.2^2. It has very little to do with relative perceived brightness. Lets say you have two 8x42 binoculars made of the same glass and coatings, but with different lens formulae, creating different FOVs. You still have the same exit pupil and same light transmission rate but I contend that the one with the smaller FOV will perform better in low light. When comparing an 8x42 to a 10x42 of the same brand and model series, the light transmission factor determines the number of photons from your subject, and the FOV and its contents determines the total number of photons delivered to the pupil. The diameter of the pupil then determines the number of photons from the subject delivered to the retina.

Steve. So if you had two binoculars with everything else the same except FOV the one with the smaller FOV would be brighter and would perform better in low light ? Would that be kind of like concentrating the beam of a flashlight so it appears brighter. My Habicht 7x42 has extremely high light transmission at 95% and a small FOV of 6.5 degrees or 342 feet and it is one of the brightest binocular's in my collection. It seems almost like the FOV is a illuminated artificially with light it is so bright. That is the reason I like it even though the FOV is narrow.

I tried the Kowa on the night sky for awhile tonite and I was surprised how good they were for a 32mm aperture. I compared them to my 12x50 SV's and of course the bigger binoculars were able to resolve fainter stars but the wide field view through the Kowa was really nice. The Moon had excellent contrast and resolution and there was very little if any CA on the limb so the glass in the Kowa corrects for CA very well. The SV in that respect was not appreciably better. I saw more ghosting in the SV's than I did the Kowa's so think they are actually better in this respect. Open clusters looked really good in the Kowa but again the SV would go deeper into the night sky with it's big aperture advantage. For the aperture I would say the Kowa's perform very well for astronomy as long as you realize they only have a 32mm objective but it is amazing how many more stars you will see even with a small binocular versus your unaided eyes. I found them quite enjoyable scanning around the Milky Way and the big FOV almost made it feel like you were in space. What was interesting was in my fairly light polluted skies I enjoyed the view of the Kowa 6.5x32 as much as I did the Swarovski SV 12x50 and in fact on the full moon I preferred the view through the Kowa's because the SV was almost TOO bright and had more reflection's. Using binoculars on the night sky is a good way to judge their performance for birding and the Kowa's came through with flying colors.

Steve04B, post 190,
The effect of FOV on the brightness of binoculars is zero as very well explained by different textbooks on binocular performance. One of these textbooks is from König and Köhler, "Die Fernrohre und Entfernungsmesser", Springer Verlag, 3-d edition, 1959, where they write after thourough calculations on page 79 "Der Helligkeitseindruck der dem Auge durch das Fernrohr vermittelt wird, ist von den Grosse des Sehfeldes, die ja im Leichtwert enthalten ist, im wesentlichen unabhängig". To avoid translation problems, they say simply: no effect at all of FOV on image brightness.
Gijs van Ginkel

Gijs van Ginkel,

What I understand Steve is saying there can be a difference between the actual brightness and what the eyes perceive.
There are two alternative explanations here:

1: the relative brightness is determined by the exit pupil. But with wider FOV more total light can be gathered in the field. Which in some circumstances can decrease the perceived brightness because the eye pupil shrink.

2: the total light amount is the same independent of FOV. IF that would be the case it means that the relative brightness is higher with smaller FOV.

It can't be both. I think the first explanation is the right one.

Steve, did I understand you correct here?

Kowa advise that the focus wheel of 6.5x32 is indeed aluminium.

Lee

I found this article on light adapted pupil size rather helpful.
https://jov.arvojournals.org/article.aspx?articleid=2279420

It shows that pupil diameter is affected by various factors including the diameter of the illuminated field of view. In binocular terms would be apparent field of view, not field of view. That would make sense as much of the retinal illuminance detection and regulation is now known to extrafoveal. However the brightness perception of binoculars is quite a different matter. Retinal illuminance will be a component, but effective acuity, contrast and spectal distribution of both the binocular and ambient light, amongst and other factors, will have a significant contribution.

David

Seems like this thread has been hijacked. Wouldn’t it be better to have the brightness issue as a separate topic in the main bino section? That way more folks who are interested could join in a those interested in the BDII, like myself, wouldn’t have to go through many posts of subject. Thanks in advance.

Upland said:

Seems like this thread has been hijacked. Wouldn’t it be better to have the brightness issue as a separate topic in the main bino section? That way more folks who are interested could join in a those interested in the BDII, like myself, wouldn’t have to go through many posts of subject. Thanks in advance.

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Upland
You make a reasonable point in principal but this topic started with post 147 in the context of a member considering the BDII and several other models. Advice was given in this post and subsequent posts about choosing between 32mm (such as the Kowa) and 42mm and between different magnifications, that could be relevant to other members facing similar choices for similar reasons. It is not always possible to surgically dissect the various topics that arise on threads into neat and separate threads.

Lee
Moderator

Has there been any info about the BD II XD 8 and 10X42s?

Andy W.

Troubador said:

Kowa advise that the focus wheel of 6.5x32 is indeed aluminium.

Lee

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Interesting! It sure looks and feels like plastic. Maybe it is aluminum made to look like plastic.:-O