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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Tests of the Zeiss 8x54 HT (1 Viewer)

I doubt that anybody at Zeiss is losing any sleep over this thread. These are for hunters to use in low light. I don't think many hunters will notice anything wrong, especially at very low light levels when eyesight acuity is extremely poor.

You mentioned that centrefield sharpness and contrast was quite obviously poor - I think many would notice that and I would sure hope that Zeiss doesn't think this performance is good enough for a $3000 instrument.

I don't know how a 42 mm HT would fare in your tests but my sample is the sharpest, most contrasty, most vivid and lively [most ''pop''] binocular I have ever used. I don't think there should be any reason the 54's can't equal or exceed that impression. Maybe all of us that see great things from the HT's are just too unsophisticated to see the real flaws in the optics.....
 
Henry,

Sorry for the delay in getting back to you. Many thanks for the additional data and observations, I found it very useful. It's a pity you didn't get the stopped down reading but there's plenty in your comments to suggest the HT might have have produced an extraordinarily poor value for a binocular of this status and price.

I'm not particularly familiar with the resolution x D way of expressing resolution performance but I see it's a useful way of making comparisons across different apertures. Like you, I've found an apparent limit using a home printed chart of about 125/D which doesn't sound unreasonable as about midway between the Dawes and Rayleigh values. I've now found 4 binoculars better than 130/D when stopped down to 20mm, but at full aperture they ranged between 160. and 220/D. All seemed equally 'sharp' to me but more about that later. The 189/D for the HT doesn't seem exceptionally good or bad for binoculars, but as you mention eyesight is pretty poor in low light so probably unimportant for hunters and the like. I often choose to relate the resolution to acuity and I'm uncomfortable guessing the eye's pupil diameter as 2.5mm in bright conditions. Your 90” VA gives would give a guestimated discrimination threshold of 90x2.5 or 225/D for bright light but that would considerably worse for low light. The reality might be something different of course.

I'm not sure why you concluded that the HT might have been around 6.2 arcseconds at 22mm. The difference between the FL and the HT in the centre cross photo resolutions look a great deal more than a fraction of an arcsecond, it looks like the equivalent of several steps on the USAF chart to me? That would be consistent with your observations unboosted where the HT reduced apparent acuity to 11.4”. Perhaps not the most accurate method of estimation but that would put the stopped down resolution at almost double your guess and gives a value of 228/D. From my limited stopped down chart testing, 11.4” might be reasonable for a compact model but it's at the bottom end of the usual range for full size for mid range and premium models. The 20/15 user will see a differences in sharpness when compared to better models in very good light conditions. It's entirely consistent with your comment that normally you don't see apparent resolutions difference in high quality binoculars. I'd judge the majority would have stopped down values far better than that. It just highly suggestive that the middle of the HT objective appears to be seriously bad.

Naturally some users will have visual acuities somewhat better than the average and they will be able to see differences between higher performing models. One thing I have become particularly aware of is how critical the light level is to being able to discriminate between models and particularly for getting consistent results for a chart. My peak acuity is around 400cd/m2 and I try to get close to that level for testing and comparing. In poor light my VA drops like a stone and the results are rubbish. Do you think varying light levels might explain your inconsistencies using the chart?

I mentioned at the start that the 4 binoculars with <130/D values stopped down appeared equally sharp. My results suggest that my visual threshold would usually be140-150/D in good light. I'd say that plenty of demonstration samples from the big players don't reach that standard. I've only briefly tried a couple of HT x42s at BirdFair and they looked pretty good to me at the time unlike some notable others.

I know Kimmo and yourself are very keen on the star tests and you mention that they might predict the resolution performance of the HT. Maybe I'm doing something wrong, but I've not been able to find any relationship between the patterns, apparent sharpness or stopped down resolutions. A spikey mess might be 125/D and something resembling text book might be 180/D. (stopped down). I'm sure it's telling me something, but I've certainly haven't figured out what... but I'm willing to learn. ;)

“It appears that the oddities of the aberrations in this binocular create a rare instance where the resolution visible on a lp/mm chart at low magnification is poorer than would be predicted by the true resolving power of the instrument.”

Henry, I've only estimated full and stopped down resolutions for 15 binoculars so far, and found that the instrument resolution (full aperture) is a very poor predictor of how sharp the view is going to appear, or indeed the stopped down result. The HT x54 appears to be an exception in the range of the difference but moderate relative shifts, both improving and deteriorating, appear to be the rule rather than the exception.

Of course the above includes a lot of speculation, but you've convinced me there is a problem with the HTs you and Kimmo tested and I really appreciate both your efforts. I hope to have a look for myself, but it probably won't be until the UK birdFair in August now.

Best regards,

David
 
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David,

I’ll try to address a few of your points.

“I'm not sure why you concluded that the HT might have been around 6.2 arcseconds at 22mm. The difference between the FL and the HT in the centre cross photo resolutions look a great deal more than a fraction of an arcsecond, it looks like the equivalent of several steps on the USAF chart to me? That would be consistent with your observations unboosted where the HT reduced apparent acuity to 11.4”. Perhaps not the most accurate method of estimation but that would put the stopped down resolution at almost double your guess and gives a value of 228/D. From my limited stopped down chart testing, 11.4” might be reasonable for a compact model but it's at the bottom end of the usual range for full size for mid range and premium models. The 20/15 user will see a differences in sharpness when compared to better models in very good light conditions. It's entirely consistent with your comment that normally you don't see apparent resolutions difference in high quality binoculars. I'd judge the majority would have stopped down values far better than that. It just highly suggestive that the middle of the HT objective appears to be seriously bad.”

The "centre cross" photos are full aperture where there was a difference of about two elements in resolution between the FL and the HT. Even that seems to me to understate the difference in image quality between the two at high magnification. Sometimes it seems that measurable resolution is the last thing to go when an image is degraded by spherical aberration. Because some rays are focused and some are unfocused it’s as if an almost sharp image is embedded in a gauzy haze. It looks worse than it measures.

The 8x resolution I could see with the HT was actually 12.4”, not 11.4”. About the best I could expect to see with any good 8x instrument is around 11” (my 90” acuity divided by 8). Someone with the best human acuity (20/8 or around 45” on a lp/mm chart) could do twice as well if the instrument optics allowed it. The curious thing to me about the HT resolution limitation at 8x in bright light is that it doesn’t appear to be explained by axial aberrations alone (the star-test at 22mm is not terrible the way it is at full aperture). That’s what led me to the supposition that lateral color is playing a role at 8x. Lateral color wouldn't show up in a high magnification star-test of a centered star, but it can smear detail at low magnification if it’s bad enough near the field center. If that’s what’s happening in the HT then better eyesight acuity won’t help much. I should emphasize that I'm not guessing about excessive lateral color being present, but I am guessing about it being a major contributor, along with insufficiently corrected spherical aberration, to the HT's lack of sharpness in the field center at 8x. That's largely because, based on the star-tests and what I saw looking through the binocular, I can't think of any other probable causes. Maybe somebody else can.


“I know Kimmo and yourself are very keen on the star tests and you mention that they might predict the resolution performance of the HT. Maybe I'm doing something wrong, but I've not been able to find any relationship between the patterns, apparent sharpness or stopped down resolutions. A spikey mess might be 125/D and something resembling text book might be 180/D. (stopped down). I'm sure it's telling me something, but I've certainly haven't figured out what... but I'm willing to learn.”

What magnification are you using for star-tests? A magnification that produces between 1mm and 0.5mm exit is best, above 2mm is definitely too little.

When it comes to scopes I think full aperture star-tests are highly predictive of image quality because scopes are intended to be used at full aperture and high magnification. You already know binoculars are a different story since the magnifications are so low that our eyes usually accept light only from from some central part of the objective lens in bright light. A good full aperture star-test of a binocular lets you know that there are very low image degrading axial aberrations present and things certainly won’t get any worse stopped down. You can reasonably expect a very nice sharp image in the field center, even at high magnification. A bad full aperture star-test alerts you that the optics are poor. At full aperture and high enough magnification the image will certainly be poor. However, if a poor instrument is effectively stopped down by a small eye pupil to just the central part of the objective some aberrations and defects will likely disappear and if the magnification is low enough the image can look fine. I haven't found that pattern to be random. Pretty much every binocular has lower aberrations when it's stopped down and some improvement in resolution (relative to the reduced effective aperture) can be expected. That’s how binoculars get by with the high aberrations they often show at full aperture.

“Henry, I've only estimated full and stopped down resolutions for 15 binoculars so far, and found that the instrument resolution (full aperture) is a very poor predictor of how sharp the view is going to appear, or indeed the stopped down result. The HT x54 appears to be an exception in the range of the difference but moderate relative shifts, both improving and deteriorating, appear to be the rule rather than the exception.”

In my experience, if a binocular shows a good full aperture star-test and high resolution at boosted magnification you can normally be confident of a sharp clean image in the field center under any lighting conditions at normal magnification. If the boosted magnification tests and measurements are poor, then the same tests with the aperture stopped down to an appropriate size will normally tell you how much the image can be expected to improve in bright daylight. The 8x54 HT seems to me be the odd exception by showing a worse center field image in bright light than its stopped down axial aberrations indicate it should. Once again, my best guess is that’s because of an excessive amount of lateral color, something normally thought of as primarily an off-axis aberration, piled on top of a healthy dose of spherical aberration. Frankly, I though lateral color occurring near the field center of internal focus binoculars had largely been eliminated by ED glass, but looking through the 8x54 HT was like a trip to the bad old days of the 1990’s when excessive lateral color was pretty common in expensive roof prism binoculars.

Henry
 
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Henry,

If I can pick up on a couple of those issues:

You make the point that an excellent full aperture resolution test and a good star test will predictively give a sharp clean image. I'm happy to accept that a perfect binocular will be perfect at any effective aperture. ;) However I've repeatedly found that pretty average full aperture resolutions and what look to me like bad star tests can be either appear exceptionally sharp or pretty soft in bright conditions as the iris block the image from the outer portion of the lens. An improvement may be more common stopped down but I have seen a couple of examples that do get relatively worse. Nothing like your HT tests though.

I regularly get a VA of 65” and occasionally below 60” so my sharpness criteria will be rather different to yours. I've found that unlike the full aperture resolution and star test (so far), the stopped down test is a good predictor of apparent sharpness. I'm not going to claim it's perfect. Masking the objective will often improve contrast a little and could clean up residual peripheral aberrations as you suggest. It does appear to improve resolutions values slightly. However, so far with the exception of one binocular with very basic coatings where there was a dramatic contrast improvement, all the others follow a consistent pattern. At 20mm if I get better than 7 arcseconds I'm confident it's going to be eyesight limited for me. Generally between 7 and 8.5 it's going to acceptable most of the time and more than that it's going to look soft. Different VAs will simply have proportionally different thresholds I suspect.

We have a rough value of 12.4” for the HT effectively stopped down by your iris, but I'm sure you would agree that a bit of boosting would improve the accuracy of the result. Of course with a 20mm objective a 3x boost would normally be sufficient.

Your thoughts on the possible causes of the poor result sound quite plausible, but surely the centre 20mm of the objective needs to be the first consideration?

Regards,

David
 
Henry and David,

Reading along as you guys question and answer one another is a great refresher/tutorial, thanks.

The 18 or 19 people in the world who like to split double stars with binoculars have it tough. Their pupils are wide open, because its dark, which often uncovers lumps and bumps in the outer region of the eye's lens, and as a result most/all of the binocular objective is used also, including its typically less perfect outer regions. The real kicker is, bright points of light are seen acutely by the retina's cones, quite unlike the extended and dim nebulae viewed by "deep sky" fans, which require the less acute rods to sense the object. So for that application, performance at reduced aperture offers no escape from the truth.

My 10x56 FL beats anything I've ever seen at this game, compared magnification to magnification, save the small-pupiled little 8x30 Fujinon FMTR-SX. Henry, I though at one time you were going to get a 10x54 HT to test too. Did that pan out? That would be the one to tempt me, once upon a time, maybe.

Ron
 
Ron,

Yeah, double stars have to the most brutal test. All the aberrations hanging out and tiny points to separate. I'm afraid to look.

I don't think I'll be testing a 10x54. I've had enough for a while.

Henry
 
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Ron,

Yeah, double stars have to the most brutal test. All the aberrations hanging out and tiny points to separate. I'm afraid to look.

I don't think I'll be testing a 10x54. I've had enough for a while.

Henry

Henry:

I enjoyed reading your tests of the HT 54, and found the poor results surprising as many would.

With all optics makers the new models are always made better.

I appreciate your optics evaluations, well done and with a comparison.

Your posts have placed some pressure on the design and manufacturing team at Zeiss I suspect and hope.

The Victory is supposed to be mfr. in Germany, and I expect the results
to match, the highest level.

The other mention I will make, is the Chinese mfr. model, which is to make things "just good enough".

Jerry
 
Henry,

Thanks for the excellent job you have done again. It must have taken quite a number of hours to do the tests and put it all together.

I’m posting here a summary of sorts of my findings with the HT line, which really do parallel what you found, well within expected sample variation range. Some of this stuff I have posted on another thread here, and some has been in personal correspondence with Henry. I’ve edited it a bit for clarity.

First some comments from my first encounter with a 10x54 Victory HT at the local shop. I got to try it outside in cloudy/partly cloudy weather with a little bit of mist, so grey, low-contrast lighting. I did not have lots of time available, so did not attempt to mount them or to boost the magnification. There was just one sample.

On a digital scale it weighed 1070 g with no straps or guards. Handling is nice, with good balance and easy focus. Focus wheel was smoother than what I recall from the 42 mm HT's.

I was surprised and disappointed by the image quality of this sample. I came to the store after about an hour of birding, and my first impression was that the image was distinctly inferior to what I get with my now rather old Canon 10x42 IS L. There was rather obvious CA even on axis, and contrast was not at all impressive. There was a couple shopping for 10x binoculars for the wife (husband has Swarovision 12x50) trying out Swaro SLC 10x42 and SV 10x42, and they both thought (as did I) that the image of the 10x42 SLC was distinctly better than that of the Zeiss 10x54 HT. The difference was a bit like that between a top-quality scope and medium-tier 80 mm ED scope at 40-50x. A difference in purity, contrast, color rendition and snap. Or, thinking of binoculars, like the difference between a Swarovski and a mid-prized roof. I'm being harsh here, but I was expecting much better. I was doing quick back-and-forth between the 10x54 HT and the 10x42 Canon (not using the stabilizer), and every time the Canon image felt sharper, contrastier and more natural.

Then some comments about the Zeiss 8x54 Victory HT. These are combined from three different occasions but with the same binocular. On two of these I also used a Zeiss 3x12 tripler to look at glitter points and USAF glass slide resolution pattern with the binoculars tripod-mounted.

The short of it is that this particular sample of the HT had really excessive spherical aberration in both barrels. Outside of focus showed a bright pink central dot with what should have been diffraction rings being a vague haze of greenish light, while inside focus images showed a very bright yellow-green outer ring with much dimmer and redder inner rings. It is hard for me to guess how much under corrected SA there actually was, as I have not seen photos with this much and don't have the aberrator functioning at present. Looking through the booster, the star-test patterns of the 8x54 I saw were actually even worse than those in Henry’s photos.There was no miscollimation or astigmatism to speak off, but with this much SA that did not salvage much. The sample I viewed also did not have the anomaly visibly in Henry’s left-barrel photos.The line-pair target looked mushy and low-contrast both through the booster and with naked eyes.

Looking at a yard of gravel or a field with the 8x54 HT, it felt like my eyes needed to do a bit of adjustment every time I moved them to a different part of view field.

There were two of us studying the resolution target (USAF Edmund optics glass slide), and unboosted, we could resolve about 1-2 elements less with the 8x54 HT than with a Zeiss 8x56 FL or a Swarovski 8x42 SLC. The 8x56 FL had, at full aperture, quite a lot of spherical aberration also, but not as much as the HT. The SLC had much less SA, and although with the steps in the resolution target we did not resolve a smaller pattern with it than with the big FL, the image looked subjectively cleaner and had better contrast. It also snapped to focus more decisively.

And finally, I went back to look at my notes on the star-test of the 8x42 HT I had reviewed in early 2013 for the Linnut magazine. I checked two units, and both had exhibited unusually high levels of spherical aberration, more in one barrel than the other, with the worse sides having a very similar look to the patterns seen in Henry’s photos for the 8x54 HT. An unusual thing was that in both of these 8x42’s, the weaker side showed in best focus through the booster three rather bright diffraction rings around the central dot, meaning that the barrel was not able to bring light to anything like a focused point.

Looking at the resolution targets, the 8x42 HT visually and unboosted, showed slightly weaker resolution than a Swarovski 8x42 SLC HD, but the difference was considerably more subtle than that between the 8x54 and 8x56 Zeiss.

Kimmo
 
I've posted this on the forums before with no response. Seems to correlate pretty well with Henry's findings on the 54mm.

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5672577/Main/5672493




I did use the 8x42 HT vs a 70 years old zeiss 8x60 outside a shop and wasnt happy with the HT

All response at the Forum was this :
Well, there was one user that wanted to pitch the HT in the dustbin after a brief viewing in a shop, so it's not unanimous.:king:
 
What were the differences between the 8x60 and the HT ??

I have a number of 8x60s and yes, they are good optically, but they are porros, heavy and cost a fortune to build.

If the equivalent of an 8x60 was produced today it would probably retail for $15,000. The 8x60s were built for military contracts where money is no obstacle.
 
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My thoughts was that the HT should be a wow . Yes it was bright . But I wasnt happy with the view . I did have trouble to get it sharp at 3 km distance

The 8x60 is a spesial order for sweden in 1941 . Left version . Seems to be only one made . Maybe I have found myself a very very good one.
 
I am sure you have found a good one and I am sure you are very lucky.

Unfortunately, as you said, you may have the only one in the world so no-one else can experience the optical pleasures that you do.

As most birders would not want to carry an 8x60 around with them (especially if it is a deck mount version) I suppose they will have to put up with lesser binoculars like the HT.

Gary.
 
Dont worry -I do know its too heavy to walk around with for hours.

I did only bring it with me to the shop to check if the Ht was good enough vs the old one . I was going to buy myself a HT but it didnt happened . I wasnt happy with the HT .
The 8x60 is normal in use at home . view is 50 m and up to 60 km distance . IF and the okulars is always standing on : 0 . No need for adjusting anything
I am now waiting for the SF to be available.
 
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I hade a few minutes with the 8x54 HT:s today,
I can agree they are very sensitive to eye placement,
saw a lot of CA and a soft image, but it seemed to decrease when positioning eye perfectly,
very strange phenomenon, and very confusing,
perhaps you could adapt your brain/binocular handling to this?
 
I'm not sure why anyone would want to try to adapt to the hypercritical pupil position demanded by the 8x54 HT. So many other binoculars better it for central sharpness and don't require any special effort. Previously I had thought one of the advantages you could reasonably expect from any large exit pupil binocular was an easy relaxing view, uncritical of pupil position.
 
I hade a few minutes with the 8x54 HT:s today,
I can agree they are very sensitive to eye placement,
saw a lot of CA and a soft image, but it seemed to decrease when positioning eye perfectly,
very strange phenomenon, and very confusing,
perhaps you could adapt your brain/binocular handling to this?

A new phenomenon is born: "rolling eyeball."

I think Henry said it best:

"So many other binoculars better it for central sharpness and don't require any special effort."

Like Clyde Crashcup and Leonardo, it's time for Zeiss engineers to go back to the drawing board after a failed experiment. They should also hire Henry to help them redesign it.

Brock
 
Maybe it was designed by a computer without much skilled human input.
Good human designers are getting more difficult to find nowadays as the oldtimers with vast experience retire.
 
Man, I had thought the 10X54's HT's would be my grail glass. Sigh.

So, I am no longer waiting to place an order with B&H Photo for 10x54's based on this thread. Do you think Zeiss will correct this? Do I keep waiting? Go for the 10X42? Another sigh.

I have a great pair of Zeiss 7X50 Marine, so I wanted the extra reach of the 10X54's. So, I'll be just as happy with the 10X42 HT's right (except at the break of dawn and the end of dusk)? Those HT 42's are free of the problems described here in the 54's?

Thank you.
 
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