Are the lemons just miscollimated cherries? (1 Viewer)

Hi All,

Unacceptable sample variation is said to exist even in most expensive optical products. Fortunately many of the top manufacturers dutifully repair or even replace clearly defective products. But how about those samples which are within acceptable tolerances, but noticeably (eg. in star tests) out of what could be - or those samples that the manufacturer's local service has not always been able to repair. If we pay something like $1500-2500€ for the best possible optics, I know I would have hard time accepting that eg. the left barrel of the binos is slightly out of alignment - even though it would be within tolerances and I couldn't see it in birdwatching .

Now that we have some of the worlds best experts on optical repairs as forum members (Bill Cook, Antony Kay), it would be interesting to hear how many of those less than perfect (or even so-called "lemon") scopes or binoculars could be serviced into cherries? In the Forum's Resources list there is a link to Antony Kay's Optrep company, which offers full services for binoculars and telescopes for £30-50 including cleaning, collimation, lubrication, nitrogen purging etc. That sounds like a reasonable cost if it turns out that its optical elements are poorly assembled or knocked out of alignment.

It would also be nice to hear from members, who have used these kinds of services, have you been happy with the results.

Best regards,

Ilkka

iporali said:

Hi All,

Unacceptable sample variation is said to exist even in most expensive optical products. Fortunately many of the top manufacturers dutifully repair or even replace clearly defective products. But how about those samples which are within acceptable tolerances, but noticeably (eg. in star tests) out of what could be - or those samples that the manufacturer's local service has not always been able to repair. If we pay something like $1500-2500€ for the best possible optics, I know I would have hard time accepting that eg. the left barrel of the binos is slightly out of alignment - even though it would be within tolerances and I couldn't see it in birdwatching .

Now that we have some of the worlds best experts on optical repairs as forum members (Bill Cook, Antony Kay), it would be interesting to hear how many of those less than perfect (or even so-called "lemon") scopes or binoculars could be serviced into cherries? In the Forum's Resources list there is a link to Antony Kay's Optrep company, which offers full services for binoculars and telescopes for £30-50 including cleaning, collimation, lubrication, nitrogen purging etc. That sounds like a reasonable cost if it turns out that its optical elements are poorly assembled or knocked out of alignment.

It would also be nice to hear from members, who have used these kinds of services, have you been happy with the results.

Best regards,

Ilkka

Click to expand...

Lovely title, and not as bananas as it sounds. In fact it's a peach of a question.

Leif

iporali said:

It would also be nice to hear from members, who have used these kinds of services, have you been happy with the results.

Click to expand...

... and is the remainder of your 10/30/Lifetime warranty still valid?

Andy.

Hi Ilkka,

Are you specifically interested in "miscollimation," which is how the post is worded, or all manner and kind of unacceptable variations? Lots of things might come under the rubric of "repairs," but some are adjustments, some are parts replacements, and some are really custom mods for specialized applications.

Two general thoughts come to mind. First, if the binoculars were designed and purchased for birding or nature observation, top-end products should not compromise these applications. However, manufacturers need not be held accountable for small variations that only a well-equipped hobbyist would find with special equipment. Part of the problem is that "ignorance is bliss" or knowledge can be anguish.

Just for giggles let me ask this question. What would we think about top-end manufacturers grading their own products into two categories, A and B, with a premium charged for the better "A" binoculars? This would not require a change in quality control practices, only pre-picking the "cherries" for higher prices.

Best regards,
Elkcub

Funny this topic should come up. Your hypothetical scenario is my reality. A couple of weeks ago, I visited a excellent optics shop run by a forum expert and I brought my 8x30 SLC's for comparison with the latest and greatest binos currently available. I mention to the knowledgable salesman that my binos are sharp but a little soft at the field edge. I figure he would tell me that the 8x30's are a wide angled binos and this was the norm but he offered to look at it through their collimator just to check. I have never dropped these binos and I take very good care of them since they were a gift from my wife for our anniversary 7 years ago. Well to his surprise, he told me that my binos were slightly out of collimation and showed me on the collimator (not that I knew what I was looking at). He said they were probably within tolerances and not noticeable when in use but he was surprise this was the case for an expensive bino. I am now disappointed and have not picked them up as much as I used to. I am going to keep this bino since it has sentimental value but I sure wish I didn't know about the deficiency. Should I get this repaired, since I can't see the difference, I will leave it alone. So my point? Ignorance IS bliss in this case.

Toothless9 said:

1) ... he told me that my binos were slightly out of collimation
2) ... He said they were probably within tolerances
3) ... and not noticeable when in use
4) ... but he was surprise this was the case for an expensive bino.
5) ... I am now disappointed ...

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Arggggg, — that sounds passive-agressive to me, my friend. I would suggest that you send those precious 8x30 SLCs to Swarovski, after calling customer service for authorization and explaining they may be slightly out of alignment through continued use. When they come back just enjoy them again. Mine were reconditioned after 12 years and now I can't put them down.
http://www.birdforum.net/showthread.php?t=31205

Best wishes,
-elk

iporali said:

Unacceptable sample variation is said to exist even in most expensive optical products. Fortunately many of the top manufacturers dutifully repair or even replace clearly defective products. But how about those samples which are within acceptable tolerances, but noticeably (eg. in star tests) out of what could be - or those samples that the manufacturer's local service has not always been able to repair. If we pay something like $1500-2500€ for the best possible optics, I know I would have hard time accepting that eg. the left barrel of the binos is slightly out of alignment - even though it would be within tolerances and I couldn't see it in birdwatching .

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Those who are not interested in optics can jump directly to the Conclusion.

Finally I have star tested 5 binoculars in the same conditions :
Zeiss 10x42 FL, Zeiss Classic 10x40, Meade 10x50 (a cheap bin internally stopped down to 40 mm, noted "10x40 sample A"), another sample of the Meade 10x50 ("10x40 sample B"), and a cheap 10x25 binocular. I have also included the results for my Zeiss FL before it was fixed by Zeiss.
This represents a total of 12 barrels examined.
I have rated each barrel with a mark between 1 and 8 : 1 for perfection, 8 for the poorest diffraction pattern. This scale is highly subjective, and imprecise : the gap between the marks 7 and 8 is much more significant than the gap between the marks 1 and 2. Furthermore, it is difficult to compare diffraction patterns with highly different errors. The 10x25 has a diffraction pattern clearly larger than the other binoculars, due to the small aperture, and is difficult to compare with others.
However, an interval of two points (for example between 4 and 6) represents a definite and very obvious difference.
Here are the results :

10x25, Left : very strange diffraction pattern, the Airy disc is elongated. Not so bad. 4
Right : a big amount of astigmatism. 7
10x40 sample A, Left : a huge amount of astigmatism. The focused pattern is awful. 8
Right : stunning ! Absolutely perfect ! 1
10x40 sample B, Left : coma, three arcs visible at focus. 4
Right : the same amount of coma, but with a different angle. 4
10x40 Classic, Left : excellent, only a pronounced and somewhat coloured first ring, probably due to chromatic aberration. 2
Right : identical to the left barrel. 2
10x42 FL before, Left : a visible amount of spherical aberration, and a big amount of coma, three or four arcs at focus. 6
Right : the same amount of spherical aberration, and a moderate amount of coma. 4
10x42 FL fixed, Left : again spherical aberration, a very slight amount of coma. The airy disc is not so clearly defined, and exhibits some colours. 3
Right : again spherical aberration, some colours on the Airy disc, but a pronounced coma. 5

Now here are my impressions of sharpness when looking trough the binoculars in normal use :

10x40 Classic (2/2) : exceptional. Unbeatable on stars.
10x42 FL fixed by Zeiss (3/5): exceptional. The view through this binocular doesn’t seem as natural as the Classic, but the difference is too small to be objectionable.
10x40 sample B (4/4) : exceptional. Not quite as good as the FL and the Classic only on stars.
10x42 FL before repairing (6/4): excellent, but not as impressive as the three above. Disappointing on stars, given their price.
10x40 sample A (8/1) : very good sharpness, excellent for the price !
10x25 (4/7): really disappointing. Poor binocular

Conclusion :
It appears that a big amount of aberrations is necessary to introduce visible changes in the image for an average eyesight. ( The result for the 10x25 suggests that this is not true for small binoculars, for which tolerances must be very tight ) . My conclusion is that if a binocular A appears sharper on axis than a binocular B, the only reason is that the optical components in the binocular A are better fitted than in the binocular B. The brand, the model, or the optical design have nothing to do with on-axis sharpness. Obviously, manufacturers, even the most prestigious ones, rely on this phenomenon to make binoculars with very large tolerances. Sometimes, these tolerances may be a bit too large for some demanding users.
So, all the comparative reviews stating that, for example the Leica XXX is sharper than the Swarovski YYY are totally meaningless, it’s only a matter of sample variation. That’s the reason why we can always find another review saying that the Swarovski YYY is sharper than the Leica XXX.
Finally, the practical advice generally given, “try before you buy”, must be understood as : “try not only several brands and several types of binoculars, but also try several specimens of the same type of binocular.”

Jean-Charles

Jean-Charles,

Thanks for this fascinating analysis. Nicely done! It certainly reinforces the notion that meaningful comparative reviews should use three or more binoculars of each type, so we can understand both within- and between- product variations. :t:

Regards,
Elkcub

Jean-Charles,

Thank you so much for taking the trouble to perform your analysis. That was a really informative piece of work and shows how powerful tool star testing is in expert's hands.

If I read your conclusions correctly, the most significant imperfections in your binoculars are various aberrations of the lenses, and not so much miscollimation. Or what do you think, could the binos be improved without changing lenses just by having them carefully collimated?

Best regards,

Ilkka

Excellent work and very interesting, Jean-Charles. I have one question about the Meade 10x50 (sample A). Do I understand correctly that you saw no spherical aberration at all in the right side? Diffraction rings were completely symetrical on both sides of focus?

I've had some recent experience that might help explain why you found that such large aberrations produced such small effects in "normal viewing", and why the one exception was the 10x25.

When I recently star tested a Nikon 8x30 E I found the left side to be good enough (perhaps a 2 or 3 on your scale), but the right side had considerable astigmatism (probably a 7 or 8 on your scale). Resolution also measured worse on the right side (4.5" left vs 7" right) and the image with boosted magnification looked worse, very soft and difficult to bring to good focus, as I expect with astigmatism. However when I simply looked through the right side in sunlight without boosted magnification the image was not bad, approximately equal to the left. Part of the explanation was of course the forgiving nature of low magnification, but an additional reason was that I had star tested the full 30mm aperture of the binocular, while in "normal use" in daylight I was only actually only using about the center 20mm. When I fitted a 20mm stopdown mask over the objective and star tested again much of the astigmatism was gone. You may have already read all that since it was in my EII review. Later, I also retested the resolution of the right side with the 20mm stopdown in place and found that it actually improved to about 6" and the image quality with boosted magnification was much cleaner and easier to focus. Then I moved indoors to a darkened room and looked directly through the binocular at a dimly lit target at about 6m. Now that my eye was open wide enough to use the entire 30mm objective I could easily see the softening effect of the astigmatism in the right side without needing to boost the magnification. I found I could actually watch the effect of the astigmatism appear and disappear by quickly removing then replacing the 20mm stopdown. In the case of small exit pupil binoculars like your 10x25 the full aperture of the objective is almost always being used, even in sunlight, so that optical defects seen in star tests of the full aperture are more likely to actually visibly degrade the image quality at "normal use" light levels, and of course those defects will probably look worse at 10x than at 7 or 8x.

Hmm.... I'm definitely no expert, just a curious beginner, but I made this following observation...

I've tested 3 Zeiss 10x40Bs (one used, one new and my pair) against 2 10x42 SLCs (one new, one used), and all five are very similar in overall view. One of the 10x40bs was a bit softer. Out of the remaining 4, after about an hour of sitting there and going back and fourth from one bin to the next, moving from test location to test location... 5-7 mile distant mountain ridge line; shady patch under trees at about 40 yards, trees with high contrasting leaves at 100yards, a grid pattern at 30 yards, a busstop billboard (text) at about 100 yards, and various other spots.

I was surprised to see that Cabela's $799 Classic 10x40b offering was pretty much on par with the SLCs ...slightly softer edge sharpness, slightly better sweet spot, a little more contrast than the SLC, but just very slightly less resoultion.

I wish I had a 10x42 Trinovids to compare them with, but I did have a pair of 10x42 Ultravids to use as reference... I'm sure it's not a surprise, but the Ultravid was easily better in every aspect.

Anyways, I looked for sample variation, but didn't really find any. Then again, I'm not an opthamologist.

Thank you for the comments. |=)|
I have corrected a little mistake in my previous post : the 10x25 binocular is rated (4/7) instead of (4/6). This changes nothing in my conclusion.

Jean-Charles

iporali said:

If I read your conclusions correctly, the most significant imperfections in your binoculars are various aberrations of the lenses, and not so much miscollimation. Or what do you think, could the binos be improved without changing lenses just by having them carefully collimated?

Click to expand...

Ilkka,

The coma is generally the sign of a miscollimated objective. So each time there is “coma” in my description, I presume that the sharpness could have been improved if the lenses have been correctly placed. I don’t know the origin of astigmatism, I wonder if it appears in a doublet when a lens is shifted relative to the other. If so, a proper manufacture of the doublet would have improved the binocular, without changing the lenses. Of course, the lenses themselves can also differ from the ideal specifications.
In fact, I don’t know WHERE lies the major part of errors in optical instruments, binoculars or not, and I would like to have the answer, but I presume that those who know the answer prefer keeping the information for themselves and their company.
I don’t know if badly fitted binoculars are easy to repair. For my Zeiss FL, if I have correctly understood my dealer, Zeiss has changed the “running lenses” in the binocular, probably the focus lenses.

Jean-Charles

henry link said:

I have one question about the Meade 10x50 (sample A). Do I understand correctly that you saw no spherical aberration at all in the right side? Diffraction rings were completely symetrical on both sides of focus?

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Henry,

In my descriptions, I have reported only visible aberrations. So the right barrel of the “Meade sample A” has no astigmatism, no spherical aberration, and no coma. However, I can’t see the diffraction rings in the out of focus patterns. This is due in my opinion to the fact that I use a too low magnification for star testing (50x for 10x binoculars, thanks to a 5x monocular), and because there is chromatic aberration. This is visible because the colours if the large out of focus discs differ in each side of focus. Unfortunately, I have not the skill to evaluate the amount of C.A. in a star test, I have never star tested astronomical instruments. I remember you gave me a tip a few months ago to look at C.A., but I haven’t performed this test. So, when I said “perfect”, this does not mean a polychromatic strehl ratio superior to 0.95.

About your explanations, I agree with you.
However I must say that the Meade A remains very good even in low light conditions. It’s very surprising for me given the awful star test in the left side. I suppose that the excellent right side compensates for the weakness of the left side. This binocular is not as sharp as my other 10x binoculars, but it provides a very good image, and is very pleasant in use.

I have read indeed your review of the Nikon EII. It was a great review, with very useful comments.

In another thread, I mentioned that I could not correlate the resolution with a booster to the resolution without a booster. I was wrong. There is definitely an interesting correlation between the star test, the resolution measured with a booster, the contrast of the image with a booster, and the perceived sharpness in normal use. My previous experiments were not rigorous enough. For the 10x42 FL, I found a resolution of 8.6” in normal use with both eyes, 4.8” in the left side with the booster, and 5.6” in the right side. I think these values depend a lot on the conditions of the test. For my taste, the easiest ways for evaluating sharpness are the star test with a booster, and the examination in low light conditions of a complex target, like irregularities in a concrete wall, a bark of a tree, or a small writing. Looking at stars at night with the binocular tripod mounted seems a very harsh test, but not so easy to perform in a store.

I have understood why the Airy disc in the 10x25 is elongated. Of course the prisms are not phase coated !
http://www.birdforum.net/article.php?a=4

Jean-Charles

xenophobe said:

Hmm.... I'm definitely no expert, just a curious beginner, but I made this following observation...

I've tested 3 Zeiss 10x40Bs (one used, one new and my pair) against 2 10x42 SLCs (one new, one used), and all five are very similar in overall view. One of the 10x40bs was a bit softer. Out of the remaining 4, after about an hour of sitting there and going back and fourth from one bin to the next, moving from test location to test location... 5-7 mile distant mountain ridge line; shady patch under trees at about 40 yards, trees with high contrasting leaves at 100yards, a grid pattern at 30 yards, a busstop billboard (text) at about 100 yards, and various other spots.

I was surprised to see that Cabela's $799 Classic 10x40b offering was pretty much on par with the SLCs ...slightly softer edge sharpness, slightly better sweet spot, a little more contrast than the SLC, but just very slightly less resoultion.

I wish I had a 10x42 Trinovids to compare them with, but I did have a pair of 10x42 Ultravids to use as reference... I'm sure it's not a surprise, but the Ultravid was easily better in every aspect.

Anyways, I looked for sample variation, but didn't really find any. Then again, I'm not an opthamologist.

Click to expand...

xenophobe,

I urge you to read this thread :
http://www.birdforum.net/showthread.php?t=26991

This was the very first time I learned that sample variation exists even in most expensive binoculars. In this example the Trinovid is sharper than the Ultravid. I’ve read several reviews saying that the Zeiss Classic 10x40 is better than the Trinovid. And you said than the Ultravid outperforms the Classic…
----> SAMPLE VARIATION !

Jean-Charles

I just read that thread again. (first time was when I first got here, lol)

I would assume sample variation, but there was no mention of the 10x coming into play, and assume that one design might be particularly suited or perform better at a certain magnification/obj size than another.

The Ultravids I used outperformed the Classic and SLC by an easily distinguishable margin.

You are right, I have mixed up the magnifications.

However, according to the 12 star tests of my binoculars, it is for me absolutely impossible that the design alone is the cause of differences in sharpness, even in 10x40 binoculars.
I remember someone (Henry Link or Kimmo Absetz ?) saying that the diffraction patterns of binoculars always exhibit various amounts of coma, astigmatism, pinched optics, and chromatic aberration. The first three aberrations are unsymmetrical, and therefore have nothing to do with optical design. C.A. may be due to optical design because it is symmetrical, however according to theory a 40mm F/4 cemented doublet has very few C.A, and surely not enough to decrease sharpness at 10x. I wonder now if even C.A. that some users see in binoculars is not as well an effect of sample variation. The only designed aberration I saw which was in my opinion due to design was the spherical aberration in the Zeiss FLs. But here again, it is impossible that this aberration alone causes visible damages in the image.
I would be glad to change my opinion if I am wrong, but I am afraid that my arguments are serious.

Jean-Charles

jcbouget said:

xenophobe,

I urge you to read this thread :
http://www.birdforum.net/showthread.php?t=26991

This was the very first time I learned that sample variation exists even in most expensive binoculars. In this example the Trinovid is sharper than the Ultravid. I’ve read several reviews saying that the Zeiss Classic 10x40 is better than the Trinovid. And you said than the Ultravid outperforms the Classic…
----> SAMPLE VARIATION !

Jean-Charles

Click to expand...

Let us keep our feet on the ground: of course there is sample variation, but in this class it is not visible (as long as there are no defects).

A Leica Trinovid cannot outperform a Leica Ultravid in sharpness. How should it do this?

A Zeiss Classic better than a Trinovid? Nonsense. Same nonsense if somebody says a Leitz Trinovid outperform a Zeiss FL.


THE MOST ANNOYING CRITISISM DURING A DISCUSSION IS DONE BY MENTIONING FACTS.


Walter

Jean-Charles: Is the Meade 10*'50' a porro or roof prism instrument?

I have on several occasions used resolution targets and real objects to compare top grade 8x40-ish bins with budget ones. Each time I find that the budget ones do not provide the same amount of detail as the expensive ones. A Nikon 8x42 HG easily bested a Nikon 8x40 Egret and a Zeiss 8x42 FL easily bested a budget 8x40 roof prism instrument. In the latter case the difference was not insignificant, whereas in the former case it would not have made that much difference when hand-holding the instruments. Could it be that the 10x50 had longer focal length objectives, and hence when stopped down to 10x40, you were only using the best part of the objectives, and they would have been operating at a larger F ratio than for the other bins? Hence aberrations would have been reduced by design, independent of manufacturing quality and coatings. (Yes I know that in daylight the eye's pupil effectively stops down the objective, but the argument still holds even if stopped down to an 8x16 instrument!) That might explain why a modest supposedly 10x50 instrument equalled the posh ones, at least in terms of on-axis resolution. I'm sure the Meade had awful contrast!

But I would not really want to compare the sharpness of two top grade 8x40-ish bins, since as you say sample variation within one product might well be comparable to the small differences between products.

Leif

Leif said:

Jean-Charles: Is the Meade 10*'50' a porro or roof prism instrument?

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It's a porro prism binocular. The focal length of the objective is 180 mm. Stopped down to 40 mm, the effective focal ratio is indeed 4.5 .
This binocular has a single layer coating on all surfaces. Of course the contrast is not in the same league than the Zeiss, but is not awful. I don't like its yellow image

Jean-Charles