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Old Wednesday 5th October 2011, 17:12   #1
henry link
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Measurements and Tests of Zen-Ray 10x43 ED3

I recently had the opportunity to evaluate two specimens of the new Zen-Ray ED3. I had hoped to write a full review of the 8x43, but that was not possible for reasons that will soon become clear. So, what follow are some measurements and the results of some tests I conducted on two specimens of the 10x43.

The binocular I will call Sample A turned out to be incorrectly labeled, both on the binocular and the box, as an 8x43. It was actually a 10x43. I donít think Iíve ever seen that happen before, but, of course, without some reference the exact magnification could be hard to estimate. If you buy one of these I would be sure to check it against a binocular of known magnification. Sample B was correctly labeled as a 10x43.

Hereís the good part first. I found the light transmission and color accuracy of the new Zens to be fully state-of-the-art. No improvements need to be made in the areas of AR coatings or dielectric prism coating to compete with the alpha brands. Beyond that, however, I didnít find things quite so rosy.

The focuser on Sample B was adequate, with just a little slop and requiring slightly more than ideal effort, a situation that might loosen up in time. However, the focuser on Sample A was quite poor, with much more slop followed by stiff jerky movements once the focuser engaged, bad enough to make accurate focus nearly impossible. I considered that focuser to be essentially unworkable under field conditions.

I measured the effective aperture by placing a transparent ruler across the objective and reading how many millimeters spanned the image of the objective at the exit pupil, by sighting through the eyepiece with a magnifier. I found the effective aperture to be slightly under spec, about 41.5mm at infinity focus and about 40mm at close focus when the positive focusing lens moves forward toward the objective and acts as an aperture stop.

Eye relief from the eye lens glass was as specified, about 15mm, but the effective eye relief from the rims of the eyecups is about 13mm from the left eyecup and, curiously, only about 11mm from the right eyecup. Thatís because the right eyecup doesnít screw down as close to the eye lens as the left cup. The right cup is also about 2mm longer than the left when they are fully extended. (See the photos of the eyecups below). I was not quite able to see the entire field in either side when wearing reading glasses.

Resolution measurements at 60x, using the USAF 1951 chart, were not very impressive. The best of the four barrels measured about 5.2 arc seconds. One barrel of Sample A was seriously defective and measured somewhat worse than the others (more about its defects below). For reference, I measured at the same time in the same set-up about 4 arc seconds for a Nikon 10x35 EII and about 3 arc seconds for a Zeiss 8x42 FL. These instrument resolution measurements donít necessarily mean that less detail will be seen at normal magnification, but they are an indication of the true quality of the optics. In this test 5 arc seconds from a 42mm binocular is mediocre at best.

The star-test photos below show the two barrels of Sample A. The bottom two photos are the right barrel (extra-focus on the left, intra-focus on the right). It has a pretty normal amount of spherical aberration for a binocular and a little astigmatism, but the patterns also indicate a rather poorly made roof prism edge, which causes the dark division of the extra-focal diffraction disk and the splitting of the central spot in the intra-focal disk. Both barrels of Sample B looked similar, which suggests that the roof prisms are just not speced to a very high standard. The top two photos of the left barrel show a very odd abnormal pattern, which may be explained by the anomalies in the moon photo and the phase correction photos to the right of the star-test photos.

I photographed the moon through the left barrel of the Sample A. Notice that it shows a focused mini-moon nestled within the main (unfocused) image of the moon. When the main image is focused the mini-image becomes an out of focus spot of light in the center of the field, which causes a loss of sharpness and contrast in that area of the field center. This is not like a normal ghost image and only occurred in this one barrel. Iíve never seen anything like it before.

This anomaly might be related to another anomaly visible in the phase correction photos at the far right below. These photos are screen shots of my computerís LCD display. They were made through the objective ends of the Zen Sample A (left barrel at top left, right barrel at top right), a non phase-corrected Brunton monocular (lower left) and a P* coated Zeiss 8x42 FL (bottom right). The camera was fitted with a polarizing filter rotated to a position that nearly canceled the computer screen light. A Porro prism binocular or roof prism binocular with good phase correction should show an almost completely dark image across the light cone just like the darkened computer screen. The Zeiss and a Nikon 8x32 SE I tried did that. The Brunton shows the half lit and half darkened light cone of a non-phase corrected roof prism. The upper right Zen photo seems to show something like partial, rather than complete, phase correction. There is something clearly very wrong in upper left Zen photo. I can only guess that maybe the phase coating was incorrectly applied or perhaps there are internal stresses in the prism glass. Anybody else have any ides? Whatever the cause, that barrel of the Zen Sample A certainly has some fascinating defects Iíve not seen in any other binocular.

I did spend some time actually looking at birds with Sample B and comparing it to the closest thing in my collection, a Nikon 10x35 EII. Besides having lower optical aberrations and a smoother focuser, Sample B was also better collimated than Sample A. I confess I donít really like 10x binoculars or binoculars with small exit pupils, so be aware that my opinion is negatively biased from the start. The Zen light transmission was excellent, visibly higher than the Nikon, even in bright sunlight, but nothing else about the experience of using the Zen was very tempting. I found that precisely setting the diopter adjustment and exactly aligning the pupils of both eyes with the optical axis were very critical for achieving a decently sharp image at the center, but I really couldnít maintain that sort of precise alignment very well while handholding at 10x. In addition, what I would call the ďsemi-sweetĒ spot was on the small side, not much over 20 degrees, which is a bit worse than the Zeiss FL, my minimum standard for a comfortable view. Overall I found the viewing experience quite a chore compared to the Zeiss 8x56 I usually use, though, in fairness I know part of the discomfort is simply the 10x and the small exit pupil. I imagine I would prefer the 8x43 and I will be interested to see the 8x42 Prime HD model with, presumably, the same excellent coatings, a better performing eyepiece and, I hope, a higher quality roof prism and better quality control.

Henry Link
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Old Wednesday 5th October 2011, 17:59   #2
james holdsworth
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Great stuff, Henry.

This is the kind of stuff I read this forum for. There are a million posts that espouse this model or that, but one well worded, well researched test like this makes them all obsolete.
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Old Wednesday 5th October 2011, 19:29   #3
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Henry,
Thanks, that is so refreshing to have to think so hard. It's not gonna get into Birder's World, though, sorry.

The phase coating demonstration is very interesting. As I understand, the light coming out of your computer monitor is linearly polarized in one direction, and the polarizing filter in front of the camera is tilted 90deg to that direction. So no light enters the camera, unless there's additional polarizing going on between the screen and the filter.

The uniformity of illumination of the Zen is so perfect in a way, it doesn't look like a screwup, and compels a search for a happy explanation. I think it is possible that the Zen is well phase corrected, but that the light comes out of the binocular rotated, rather than unrotated as in the Zeiss. As far as I know that would be possible, just a matter of a slightly different P coating. Do you think that could be? If that were the case, you should be able to find an orientation of the filter on the camera that would cause complete darkening of the field. I may be wrong about this possibility, but it would be easier to try it than to get all theoretical.
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Old Wednesday 5th October 2011, 19:40   #4
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Quote:
Originally Posted by henry link View Post
The top two photos of the left barrel show a very odd abnormal pattern, which may be explained by the anomalies in the moon photo and the phase correction photos to the right of the star-test photos.

Henry Link
Very good job Henry, lots of information.

I have no idea about the star test. A WAG might be about 5 waves of 5th order higher order spherical aberration with no other aberrations. It might account for the lousy resolution. Possibly (again, WAG) bad melt of the prism glass, but who knows.

I have attached a computer generated diffraction patter of an f:/4 that sort of resembles your test, at least as far as the main rings.

Just idle speculation on my part. I have never seen anything like it either.
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Old Wednesday 5th October 2011, 19:42   #5
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I'll leave that up there as a testament to my speculative weakness. But another possibility is, see how only blue gets through. It looks like at the very least, the P coating on the Zen is working well for the longer wavelengths. What little gets through the Zeiss is blue too, just about a hundred times less, so there seems to be a characteristic weakness of P coats for the shorter wavelengths.

How broadband is your P-coating? Great conversation starter.
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Old Wednesday 5th October 2011, 21:17   #6
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Thanks Ron (Surveyer). That does resemble the pattern.

Well, Ronh, try cogitating on the images below. They were taken the same way, but somewhat overexposed to bring out more details of the uneven transmission.

L to R - 5x25 finderscope with no prism in the light path, Fujinon 8x30 FMTR-SX Porro, Nikon 8x32 SE Porro, Nikon 7x50 Prostar Porro, Zeiss 8x42 FL Roof (phase-coated), Dakota Elite 8x32 Roof (phase-coated). (The Dakota photo is in the next post.)

Unfortunately I no longer have the Zens to photograph the same way, but they resemble the Dakota in the sense that equal illumination of the two halves of the light cone does not occur at the same rotation point as the darkest illumination for each half. As one half gets darker the other gets lighter. I'm really not sure what this test shows beyond the obvious difference between phase-coated or not. Only the non-prismatic scope is really fully and evenly darkened, even Porros appear to have random patterns of uneven polarization (what's going on with the Prostar?). In the Zen photos I was mainly interested in showing the very weird pattern of the Zen Sample A, left barrel.

Henry
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Old Wednesday 5th October 2011, 21:22   #7
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Oops, sorry, the Dakota photo didn't show up in the post. Here it is
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Old Wednesday 5th October 2011, 23:01   #9
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Henry,

After you notified me about the potential mixed up on the model, I was worried that we may have mistakenly sent out those defective units that were previously identified and put aside for repair work during the final quality inspection. Based on your report, I am almost certain that's how that mistake has occured.

Besides the final quality control we already put in place, we are going to take steps to improve our operation to prevent similar escapes from happening again.

Thanks

Charles
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Old Wednesday 5th October 2011, 23:29   #10
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Steve C said in another thread ZR switched factories with the ED3 to improve QC. Looks like with Sample A they outsourced QC to the customer!
Rick, although I disagree some of your posts with regard to our products, I do feel the same way that whenever there is an escaped defective unit, we failed to do our job by "outsourcing" our destiny into the hands of other people. For that, it's not acceptable!

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Old Thursday 6th October 2011, 00:18   #11
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Henry,

Did Zen-Ray send you these units, on your request? Or did you acquire them on your own?

I'm interested to see if this is as simple as Charles implies.
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Old Thursday 6th October 2011, 01:29   #12
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Thanks Henry for a detailed review.
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Old Thursday 6th October 2011, 01:45   #13
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James,

These were purchased by a friend, based on my recommendation, which was based on what I had read here. I emailed Charles to let him know I intended to review them when they arrived and then sent another email to inform him about the mislabeling when I saw them. I think that email must have escaped his attention because I didn't receive a reply and decided to go ahead and post my findings after about a week had passed.

I'm happy to hear that at least Sample A was known to be defective and was shipped out accidently, so anything I wrote about it should be taken in that light. All companies send out the occasional defective unit. I think some of the other findings are probably not related to sample variation, like the unequal eyecup extension, the effective aperture measurements, the off-axis performance of the eyepiece and, on the positive side, the high light transmission.

Henry

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Old Thursday 6th October 2011, 01:54   #14
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Wow, amazing thread! Nice going, Henry.
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Old Thursday 6th October 2011, 17:04   #15
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Henry,
Thank goodness that last round of images required strong exposures to get, so puzzling as it is, we are seeing a small noise effect.

I will hazard a guess as to the cause. Mechanical stress can induce birefringence in a piece of perfectly homogenous glass. In the old days when glass wasn't so good, and likely to suffer internal stresses from imperfect mixing and annealing, they used to pick out good pieces with a polarizer test. Nowadays, I suspect the stress of holding a prism in place will induce a tiny bit of birefringece in somewhat regular ways, as the stress is regular. That regularity is a part of what I'm trying to understand, ie., the patterned look of the images.

In addition to birefringene's refraction, the differently refracted beams are differently polarized. Like all refrative effects, this would be stronger in the blue. To whatever extent this is really happening (everybody's roaring with laughter by now, right?), it would cause something like what you have observed.

Ron
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Old Friday 7th October 2011, 17:09   #16
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I purchased a Zen-Ray 10x43 ED3 last month that was bad right out of the box. I couldn't get either barrel to focus clearly at the same time, and while it's kind of hard to explain, they gave a "sea sick" feeling while looking through them. I assumed this was either a collimation issue or something wrong with the focus mechanism.

I emailed Charles about the problem and he said to send them in for evaluation, which I promptly did. I exchanged emails with Charles along the way and after about a week he said a new pair had been shipped to me. The new pair arrived and were far better than the first.

Overall, I'm pretty impressed with the view of the ED3's, and in my opinion, their appearance and feel is much better than the earlier ED's (and ED2's), but I'm still not sold on their durability. Having said that, their customer service seems to be very good from my experience and Charles was easy to work with.

Don't know if it's the case of not, but after reading this thread it makes me wonder if the "faulty" pair that were sent to Henry were the ones I returned?

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Old Friday 7th October 2011, 17:17   #17
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I think Ron's idea about mechanical stress is exactly right. I tried an experiment with an old Nikon E prism, still mounted in the prism housing, but with no eyepiece or objective. I loosened the prism mounting screw I could reach and photographed the polarization pattern just as before. Then I deliberately over-tightened the screw and photographed the prism again. The far left photo below is with the loosened screw and the next one to the right is with the over-tightened screw. It's pretty obvious that tightening the screw has changed the polarization pattern, most likely by introducing a stress point at about 7:00.

Next I went through my collection of binoculars looking for something interesting. The photo on the right is a CZJ 8x50 Octarem which seems to show some unusually high stresses. This binocular has a cemented prism cluster and a unique prism mounting system with no prism shelf. This could be the way it came from the factory, but this pair was cleaned about fifteen years ago, so it's possible the tech who serviced it might have over-tightened the prisms.
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Old Friday 7th October 2011, 19:17   #18
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That's the ideal demonstration, Henry, thank you.
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Old Friday 7th October 2011, 19:44   #19
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Quite apart from the content of your tests Henry which I'm still digesting I am very impressed with the images you are able to obtain.

I recently tried to photo a star test of my new to me Nikon scope at 75x and just couldn't manage it handholding the camera. I presume I need a tripod with camera set up behind the scope eyepiece to give me more exposure time.
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Old Saturday 8th October 2011, 16:49   #20
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dipped,

The binocular star tests were done inside at 10m, using a pinhole artificial star. The exposures are about 1/8-1/20 sec, but my camera lens has vibration reduction so handholding is not too hard. Scopes need smaller point sources, so I have a outdoor set-up, using small glass balls in the sun at distances from about 30-60m. Those never turn out as well as the indoor shots. The shutter speeds are usually quite high in sunlight 1/500-1/2000 second so hand holding is OK, but even when I can see nice clear diffraction rings in the eyepiece they nearly always turn out fuzzy in the photos because of air turbulence.

Henry
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Old Sunday 9th October 2011, 05:21   #21
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I'm going to have a serious second look at my 8X43's, I just might have been a little to generous with my first general impressions.

The "slop" is what might have swayed me away from the optics......i'll let you all know how it goes from here (it's not that I noticed but i'll have a good second look)
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